life on mars research essay

• Ask An Astrobiologist
• Resources Graphic Histories Coloring Pages Heroes Posters Life in the extremes Digital Backgrounds SciComm Guild

Life on Mars: A Definite Possibility

Was Mars once a living world? Does life continue, even today, in a holding pattern, waiting until the next global warming event comes along? Many people would like to believe so. Scientists are no exception. But so far no evidence has been found that convinces even a sizable minority of the scientific community that the red planet was ever home to life. What the evidence does indicate, though, is that Mars was once a habitable world . Life, as we know it, could have taken hold there.

The discoveries made by NASA ’s Opportunity rover at Eagle Crater earlier this year (and being extended now at Endurance Crater) leave no doubt that the area was once ‘drenched’ in water . It might have been shallow water. It might not have stuck around for long. And billions of years might have passed since it dried up. But liquid water was there, at the martian surface, and that means that living organisms might have been there, too.

So suppose that Eagle Crater – or rather, whatever land formation existed in its location when water was still around – was once alive. What type of organism might have been happy living there?

Probably something like bacteria. Even if life did gain a foothold on Mars, it’s unlikely that it ever evolved beyond the martian equivalent of terrestrial single-celled bacteria. No dinosaurs; no redwoods; no mosquitoes – not even sponges, or tiny worms. But that’s not much of a limitation, really. It took life on Earth billions of years to evolve beyond single-celled organisms. And bacteria are a hardy lot. They are amazingly diverse, various species occupying extreme niches of temperature from sub-freezing to above-boiling; floating about in sulfuric acid; getting along fine with or without oxygen. In fact, there are few habitats on Earth where one or another species of bacterium can’t survive.

What kind of microbe, then, would have been well adapted to the conditions that existed when Eagle Crater was soggy? Benton Clark III , a Mars Exploration Rover ( MER ) science team member, says his “general favorite” candidates are the sulfate-reducing bacteria of the genus Desulfovibrio . Microbiologists have identified more than 40 distinct species of this bacterium.

Eating Rocks

We tend to think of photosynthesis as the engine of life on Earth. After all, we see green plants nearly everywhere we look and virtually the entire animal kingdom is dependent on photosynthetic organisms as a source of food. Not only plants, but many microbes as well, are capable of carrying out photosynthesis. They’re photoautotrophs: they make their own food by capturing energy directly from sunlight.

But Desulfovibrio is not a photoautotroph; it’s a chemoautotroph. Chemoautotrophs also make their own food, but they don’t use photosynthesis to do it. In fact, photosynthesis came relatively late in the game of life on Earth. Early life had to get its energy from chemical interactions between rocks and dirt, water, and gases in the atmosphere. If life ever emerged on Mars, it might never have evolved beyond this primitive stage.

Desulfovibrio makes its home in a variety of habitats. Many species live in soggy soils, such as marshes and swamps. One species was discovered all snug and cozy in the intestines of a termite. All of these habitats have two things in common: there’s no oxygen present; and there’s plenty of sulfate available.

Sulfate reducers, like all chemoautotrophs, get their energy by inducing chemical reactions that transfer electrons between one molecule and another. In the case of Desulfovibrio, hydrogen donates electrons, which are accepted by sulfate compounds. Desulfovibrio, says Clark, uses “the energy that it gets by combining the hydrogen with the sulfate to make the organic compounds” it needs to grow and to reproduce.

The bedrock outcrop in Eagle Crater is chock full of sulfate salts. But finding a suitable electron donor for all that sulfate is a bit more troublesome. “My calculations indicate [that the amount of hydrogen available is] probably too low to utilize it under present conditions,” says Clark. “But if you had a little bit wetter Mars, then there [would] be more water in the atmosphere, and the hydrogen gas comes from the water” being broken down by sunlight.

So water was present; sulfate and hydrogen could have as an energy source. But to survive, life as we know it needs one more ingredient carbon. Many living things obtain their carbon by breaking down the decayed remains of other dead organisms. But some, including several species of Desulfovibrio, are capable of creating organic material from scratch, as it were, drawing this critical ingredient of life directly from carbon dioxide (CO 2 ) gas. There’s plenty of that available on Mars.

All this gives reason to hope that life that found a way to exist on Mars back in the day when water was present. No one knows how long ago that was. Or whether such a time will come again. It may be that Mars dried up billions of years ago and has remained dry ever since. If that is the case, life is unlikely to have found a way to survive until the present.

Tilting toward Life

But Mars goes through cycles of obliquity, or changes in its orbital tilt. Currently, Mars is wobbling back and forth between 15 and 35 degrees’ obliquity, on a timescale of about 100,000 years. But every million years or so, it leans over as much as 60 degrees. Along with these changes in obliquity come changes in climate and atmosphere. Some scientists speculate that during the extremes of these obliquity cycles, Mars may develop an atmosphere as thick as Earth’s, and could warm up considerably. Enough for dormant life to reawaken.

“Because the climate can change on long terms,” says Clark, ice in some regions on Mars periodically could “become liquid enough that you would be able to actually come to life and do some things – grow, multiply, and so forth – and then go back to sleep again” when the thaw cycle ended. There are organisms on Earth that, when conditions become unfavorable, can form “spores which are so resistant that they can last for a very long time. Some people think millions of years, but that’s a little controversial.”

Desulfovibrio is not such an organism. It doesn’t form spores. But its bacterial cousin, Desulfotomaculum, does. “Usually the spores form because there’s something missing, like, for example, if hydrogen’s not available, or if there’s too much [oxygen], or if there’s not sulfate. The bacteria senses that the food source is going away, and it says, ‘I’ve got to hibernate,’ and will form the spores. The spores will stay dormant for extremely long periods of time. But they still have enough machinery operative that they can actually sense that nutrients are available. And then they’ll reconvert again in just a matter of hours, if necessary, to a living, breathing bacterium, so to speak. It’s pretty amazing,” says Clark.

That is not to say that future Mars landers should arrive with life-detection equipment tuned to zero in on species of Desulfovibrio or Desulfotomaculum. There is no reason to believe that life on Mars, if it ever emerged, evolved along the same lines as life on Earth, let alone that identical species appeared on the two planets. Still, the capabilities of various organisms on Earth indicate that life on Mars – including dormant organisms that could spring to life again in another few hundred thousand years – is certainly possible.

Clark says that he doesn’t “know that there’s any organism on Earth that could really operate on Mars, but over a long period of time, as the martian environment kept changing, what you would expect is that whatever life had started out there would keep adapting to the environment as it changed.”

Detecting such organisms is another matter. Don’t look for it to happen any time soon. Spirit and Opportunity were not designed to search for signs of life, but rather to search for signs of habitability. They could be rolling over fields littered with microscopic organisms in deep sleep and they’d never know it. Even future rovers will have a tough time identifying the martian equivalent of dormant bacterial spores.

“The spores themselves are so inert,” Clark says, “it’s a question, if you find a spore, and you’re trying to detect life, how do you know it’s a spore, [and not] just a little particle of sand? And the answer is: You don’t. Unless you can find a way to make the spore do what’s called germinating, going back to the normal bacterial form.” That, however, is a challenge for another day.

Suggestions or feedback?

MIT News | Massachusetts Institute of Technology

• Machine learning
• Social justice
• Black holes
• Classes and programs

Departments

• Aeronautics and Astronautics
• Brain and Cognitive Sciences
• Architecture
• Political Science
• Mechanical Engineering

Centers, Labs, & Programs

• Abdul Latif Jameel Poverty Action Lab (J-PAL)
• Picower Institute for Learning and Memory
• Lincoln Laboratory
• School of Architecture + Planning
• School of Engineering
• School of Humanities, Arts, and Social Sciences
• Sloan School of Management
• School of Science
• MIT Schwarzman College of Computing

Addressing the possibility of life on Mars

Press contact :.

Previous image Next image

In 2018, millions of people around the world caught glimpses of the planet Mars, discernible as a bright red dot in the summer’s night skies. Every 26 months or so, the red planet reaches a point in its elliptical orbit closest to Earth, setting the stage for exceptional visibility. This proximity also serves as an excellent opportunity for launching exploratory Mars missions, the next of which will occur in 2020 when a global suite of rovers will take off from Earth. 

The red planet was hiding behind the overcast, drizzling Boston sky on Oct. 11, when Mars expert John Grotzinger gave audiences a different perspective, taking them through an exploration of Mars' geologic history. Grotzinger, the Fletcher Jones Professor of Geology at the Caltech and a former professor in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS), also used the eighth annual John Carlson Lecture to talk to the audience gathered at the New England Aquarium about the ongoing search for life on Mars.

Specializing in sedimentology and geobiology, Grotzinger has made significant contributions to understanding the early environmental history of the Earth and Mars and their habitability. In addition to involvement with the Mars Exploration Rover (MER) mission and the High Resolution Science Experiment (HiRISE) onboard the Mars Reconnaissance Orbiter (MRO), Grotzinger served as project scientist of the Mars Science Laboratory mission, which operates the Curiosity roving laboratory. Curiosity explores the rocks, soils, and air of the Gale Crater to find out whether Mars ever hosted an environment that was habitable for microbial life during its nearly 4.6-billion-year history.

“What I’d like to do is give you a very broad perspective of how we as scientists go about exploring a planet like Mars, with the rather audacious hypothesis that there could have been once life there,” he told the audience. “This is a classic mission of exploration where a team of scientists heads out into the unknown.”

“Simple one-celled microorganisms we know have existed on Earth for the last three-and-a-half billion years — a long time. They originated, they adapted, they evolved, and they didn’t change very much until you had the emergence of animals just 500 million years ago,” Grotzinger said. “For basically 3 billion years, the planet was pretty much alone with microbes. So, the question is: Could Mars have done something similar?”

Part of the research concerning whether or not Mars ever hosted ancient life involves identifying the environmental characteristics necessary for the survival of living organisms, including liquid water. Currently, the thin atmosphere around Mars prevents the accumulation of a standing body of water, but that may not always have been the case. Topographic features documented by orbiters and landers suggest the presence of ancient river channels, deltas and possibly even an ocean on Mars, “just like we see on Earth,” Grotzinger said. “This tells us that, at least, for some brief period of time if you want to be conservative, or maybe a long period of time, water was there [and] the atmosphere was denser. This is a good thing for life.”

To describe how scientists search for evidence of past habitability on Mars, Grotzinger told the story of stratigraphy — a discipline within geology that focuses on the sequential deposition and layering of sediments and igneous rocks. The changes that occur layer-to-layer indicate shifts in the environmental conditions under which different layers were deposited. In that manner, interpreting stratigraphic records is simple, he said.

“It’s like reading a book. You start at the bottom and you get to the first chapter, and you get to the top and you get to the last chapter,” Grotzinger said. “Sedimentary rocks are records of environmental change … what we want to do is explore this record on Mars.”

While Grotzinger and Curiosity both continue their explorations of Mars, scientists from around the world are working on pinpointing new landing sites for future Mars rovers which will expand the search for ancient life. This past summer, the SAM (Sample Analysis on Mars) instrument aboard the Curiosity rover detected evidence of complex organic matter in Gale Crater, a discovery which further supports the notion that Mars may have been habitable once.

“We know that Earth teems with life and we have enough of a fossil record to know that it’s been that way since we get to the oldest, well-preserved rocks on Earth. But yet, when you go to those rocks, you almost never find evidence of life,” Grotzinger said, leaving space for hope. “And that’s because, in the conversion of the sedimentary environment to the rock, there are enough mineralogic processes that are going on that the record of life gets erased. And so, I think we’re going to have to try over and over again.”

Following the lecture, members and friends of EAPS attended a reception in the main aquarium that featured some of the research currently taking place in the department. Posters and demonstrations were arranged around the aquarium’s cylindrical 200,000-gallon tank simulating a Caribbean coral reef, and attendees were able to chat with presenters and admire aquatic life while learning about current EAPS projects.

EAPS graduate student, postdoc, and research scientist presenters included Tyler Mackey, Andrew Cummings, Marjorie Cantine, Athena Eyster, Adam Jost, and Julia Wilcots from the Bergmann group; Kelsey Moore and Lily Momper from the Bosak group; Eric Beaucé, Ekaterina Bolotskaya, and Eva Golos from the Morgan group; Jonathan Lauderdale and Deepa Rao from the Follows group; Sam Levang from the Flierl group; Joanna Millstein and Kasturi Shah from the Minchew group; and Ainara Sistiaga, Jorsua Herrera, and Angel Mojarro from the Summons group.

The John H. Carlson Lecture series communicates exciting new results in climate science to general audiences. Free of charge and open to the general public, the annual lecture is made possible by a generous gift from MIT alumnus John H. Carlson to the Lorenz Center in the Department of Earth, Atmospheric and Planetary Sciences.

Anyone interested in join the invitation list for next year’s Carlson Lecture is encouraged to contact Angela Ellis .

Share this news article on:

Related links.

• John Grotzinger
• Photos: 2018 John Carlson Lecture
• Lorenz Center
• Department of Earth, Atmospheric and Planetary Sciences

Related Topics

• Earth and atmospheric sciences
• Planetary science
• Space, astronomy and planetary science
• Special events and guest speakers

Related Articles

It's time to rock and rove for MIT's Grotzinger

Exploring Mars with the Curiosity rover: The search for ancient habitable environments

3 Questions: Roger Summons on finding organic matter on Mars

A brief history of environmental successes

Big ice, big science

Previous item Next item

More MIT News

To build a better AI helper, start by modeling the irrational behavior of humans

Read full story →

Researching extreme environments

Advancing technology for aquaculture

Using deep learning to image the Earth’s planetary boundary layer

New flight procedures to reduce noise from aircraft departing and arriving at Boston Logan Airport

New major crosses disciplines to address climate change

• More news on MIT News homepage →

Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, MA, USA

• Map (opens in new window)
• Events (opens in new window)
• People (opens in new window)
• Careers (opens in new window)
• Accessibility
• Social Media Hub
• MIT on Facebook
• MIT on YouTube
• MIT on Instagram

Should We Go to Mars? Carl Sagan Had Thoughts

It’d be “a step more significant than the colonization of land by our amphibian ancestors some 500 million years ago.” But Sagan had reservations.

The U.S. and Chinese governments hope to send humans to Mars in the 2030s. Elon Musk claims his SpaceX company may be able to accomplish the task even sooner. But is this a good use of Earth’s resources? Back in 1991 the legendary astronomer and science communicator Carl Sagan shared some ideas about how to think about that question.

Two years earlier, in 1989, President George H.W. Bush had announced a plan to land the first human on the red planet in 2019. (As you may be aware, this goal ultimately went unmet ). Sagan wrote that he’d been dreaming of Mars voyages since childhood, and advocating for human missions to the planet for several years. He predicted that the eventual creation of self-sustaining colonies on other plants would be an enormous milestone in history—“a step more significant than the colonization of land by our amphibian ancestors some 500 million years ago.”

But, he added, “that doesn’t mean it has to happen today. It will also be a transforming event if it happens 100 years from now.”

The central downside Sagan saw was the price tag. He cited a long list of “clear, crying national needs”—including homelessness, the AIDS epidemic and the need for alternatives to fossil fuels—that might be better candidates for large shares of the federal government’s discretionary budget.

Sagan ran down a list of common justifications for a Mars mission: Advancement of basic scientific knowledge? Useful, but probably accomplished nearly as well with far cheaper robotic missions. Promoting science education? OK, but wouldn’t it be better to just fund schools and libraries? “Spinoff” technological benefits for the domestic economy? “But this is an old argument: Spend $75 billion to send Apollo astronauts to the Moon, and we’ll throw in a free nonstick frying pan. One can clearly see that if we are after frying pans, we can invest the money directly and save almost all of that $75 billion.”

He found less tangible arguments for sending humans to Mars more convincing. Perhaps international missions could bring nations together in the wake of the Cold War. The grand adventure of space travel might inspire young people with optimism about the future. And an “emerging cosmic perspective” of humanity’s place in the universe might help in “clarifying the fragility of our planetary environment.”

Weekly Newsletter

Get your fix of JSTOR Daily’s best stories in your inbox each Thursday.

Privacy Policy   Contact Us You may unsubscribe at any time by clicking on the provided link on any marketing message.

Sagan ended his essay with suggestions for research and development projects that could support an eventual mission to Mars, while also providing other benefits. Ultimately though, he argued, the top way to support the exploration of Mars was to address pressing matters on Earth.

“Achieving even modest improvements in the serious social, economic, and political problems that our global civilization now faces could release enormous resources, both material and human, for furthering space exploration and other worthy goals,” he concluded.

Support JSTOR Daily! Join our new membership program on Patreon today.

JSTOR is a digital library for scholars, researchers, and students. JSTOR Daily readers can access the original research behind our articles for free on JSTOR.

Get Our Newsletter

More stories.

• Charles Darwin and His Correspondents: A Lifetime of Letters

Who Can Just Stop Oil?

A Brief Guide to Birdwatching in the Age of Dinosaurs

The Alpaca Racket

Recent posts.

• I Hear America Singing
• A People’s Bank at the Post Office
• London Planetrees, Moon Time, and Dunning-Kruger
• Culinary Fusion in the Ancient World

Support JSTOR Daily

Sign up for our weekly newsletter.

• April 18, 2024 | Scientists Discover Gigantic Global Reserve of Soil Carbon Underground
• April 18, 2024 | Stanford’s Innovative Blood Test Offers New Hope for Hodgkin Lymphoma Patients
• April 18, 2024 | NASA and Boeing Prep Starliner and Atlas V Rocket Prep for Historic ISS Journey
• April 18, 2024 | Remarkable Findings – New Research Reveals That the Spinal Cord Can Learn and Memorize
• April 18, 2024 | Scientists Discover Ghostly New Species 80 Feet Underground

Three Years Later, the Search for Life on Mars Continues

By University of Cincinnati April 8, 2024

In its three years on Mars, NASA’s Perseverance rover has made remarkable strides in exploring the planet’s surface, uncovering evidence of its water history and geological features that hint at the possibility of ancient life. The ongoing mission and anticipated sample return effort promise to deepen our understanding of Mars and our place in the cosmos.

In the three years since NASA ’s Perseverance rover touched down on Mars , the NASA science team has made the daily task of investigating the red planet seem almost mundane.

The rover and its helicopter sidekick Ingenuity have captured stunning images of Mars and collected 23 unique rock core samples along 17 miles of an ancient river delta.

One science team member, University of Cincinnati Associate Professor Andy Czaja, said he sometimes has to remind himself that the project is anything but ordinary.

“This is so cool. I’m exploring another planet,” he said.

Mission Highlights and Discoveries

Czaja teaches in the Department of Geosciences in UC’s College of Arts and Sciences. He is a paleobiologist and astrobiologist helping NASA look for evidence of ancient life on Mars using a rover outfitted with custom geoscience and imaging tools with three of his UC graduate students, Andrea Corpolongo, Brianna Orrill, and Sam Hall.

Three years into the mission, the rover has performed like a champ, he said.

“Perseverance has excelled. It’s been fantastic. It has such capable instrumentation for doing the geology work. It’s able to explore distant objects with its zoom lens cameras and can focus on tiny objects at incredible resolution,” Czaja said.

University of Cincinnati graduate student Andrea Corpolongo, left, and Associate Professor Andy Czaja pose in front of a telescope at the Cincinnati Observatory. They serve on the NASA science team exploring Mars with the Perseverance rover. Credit: Andrew Higley

Along the way, the mission has recorded a number of firsts: the first powered flight, the first recorded sounds of Mars, the longest autonomous drive (nearly a half-mile), and new discoveries about the planet’s geology, atmosphere, and climate.

Czaja was part of the NASA team that decided where on Mars to land the rover. And he remained on the science team that would pore over its daily data and discoveries to decide what the rover should do next.

Geological Insights

Among the new discoveries was finding primary igneous rocks in Jezero Crater. These rocks are the hardened result of liquid magma. They offer scientists promising clues about refining the known age of the planet.

Scientists suspect Mars once had long-lived rivers, lakes, and streams. Today, water on Mars is found in ice at the poles and trapped below the Martian surface.

Czaja and his student Corpolongo were co-lead authors of a paper published in the Journal of Geophysical Research, Planets that revealed that Mars also may have had hydrothermal systems based on the hydrated magnesium sulfate the rover identified in the volcanic rocks.

“When those rocks cool off and fracture, they become a habitable environment for life,” Czaja said.

Corpolongo also led a similar research paper in the same journal co-authored by Czaja detailing the results of the rover’s analysis of samples using the SHERLOC deep ultraviolet Raman and fluorescence instrument. Both papers featured contributions from dozens of their fellow NASA researchers on the project.

Samples collected by the rover may finally answer the question about whether we are alone in the universe.

The Quest for Ancient Life

“We have not found any definitive evidence of life in these deposits yet. But if there were fossil microorganisms trapped in the rocks, they would be too small to see with the rover,” Czaja said.

Czaja is hopeful funding will be approved for the anticipated Mars Sample Return mission to retrieve the hermetically sealed titanium tubes scientists have spent three years filling with interesting rock cores.

“These hydrated minerals trap water within themselves and record the history of how and when they formed,” the study said. “Returning samples of these minerals to Earth would allow researchers to explore the history of Mars’ water and climate and possibly evidence of ancient life with the most sensitive instruments possible.”

The Journey Continues

But that was just the beginning. Perseverance began its deliberate exploration from the floor of the crater to the front of the delta, formed by an ancient river or drainage channel where it encountered sedimentary rocks that often contain trapped minerals and another avenue for evidence of ancient life.

And last year the rover made it to the crater’s margin in what used to be an enormous lake where it is exploring deposits of magnesium carbonate, which can form geologically or biologically from bacteria.

Czaja said the decision to send Perseverance to Jezero Crater appears to be paying off.

“Absolutely. There were other places we could have gone that might have been just as good,” he said. “You won’t know until you explore them all. But Jezero was picked for good reason and it has been completely justified.”

The helicopter Ingenuity’s flying days appear to be over after it sustained rotor damage in January after landing on its 72nd flight. But Perseverance is still going strong. It still has 15 sample tubes at its disposal to capture additional interesting geologic specimens.

Next the rover will make its way out of Jezero Crater to explore the wider area. Czaja said they are likely to find rocks dating back 4 billion years or more. And Mars could harbor stromatolites or rocks that contain evidence of ancient layered mats of bacteria visible to the naked eye. On Earth, these rocks are sometimes found in extreme environments such as geyser basins.

The horizon of discovery continues to expand daily before the science team.

“I hope that Perseverance has just whetted our appetite for more Martian exploration,” Czaja said. “And bringing back samples will allow us to study Mars and search for evidence of ancient life with instruments that haven’t even been invented yet for years and years to come.”

Reference: “Evidence of Sulfate-Rich Fluid Alteration in Jezero Crater Floor, Mars” by Sandra Siljeström, Andrew D. Czaja, Andrea Corpolongo, Eve L. Berger, An Y. Li, Emily Cardarelli, William Abbey, Sanford A. Asher, Luther W. Beegle, Kathleen C. Benison, Rohit Bhartia, Benjamin L. Bleefeld, Aaron S. Burton, Sergei V. Bykov, Benton Clark, Lauren DeFlores, Bethany L. Ehlmann, Teresa Fornaro, Allie Fox, Felipe Gómez, Kevin Hand, Nikole C. Haney, Keyron Hickman-Lewis, William F. Hug, Samara Imbeah, Ryan S. Jakubek, Linda C. Kah, Lydia Kivrak, Carina Lee, Yang Liu, Jesús Martínez-Frías, Francis M. McCubbin, Michelle Minitti, Kelsey Moore, Richard V. Morris, Jorge I. Núñez, Jeffrey T. Osterhout, Yu Yu Phua, Nicolas Randazzo, Joseph Razzell Hollis, Carolina Rodriguez, Ryan Roppel, Eva L. Scheller, Mark Sephton, Shiv K. Sharma, Sunanda Sharma, Kim Steadman, Andrew Steele, Michael Tice, Kyle Uckert, Scott VanBommel, Amy J. Williams, Kenneth H. Williford, Katherine Winchell, Megan Kennedy Wu, Anastasia Yanchilina and Maria-Paz Zorzano, 24 January 2024, Journal of Geophysical Research: Planets . DOI: 10.1029/2023JE007989

The study was funded by the Swedish National Space Agency, NASA Headquarters, the U.S. National Science Foundation, and the UK Space Agency.

More on SciTechDaily

Earth and Mars Were Formed From Collisions of Large Bodies Made of Inner Solar System Material

CDC Warns of Cow-to-Human Transmission of H5N1 Bird Flu in Texas

Serial Dependence Bias: Guessing Coins’ Value Quickly Demonstrates Cognitive Bias Mechanism

Nanocrystals With Unique Surface Texture That Eradicates Bacteria Biofilm

The awe-inspiring mars relay network that will keep nasa’s perseverance in touch with earth during landing and beyond.

Thruster Test on Leaking Soyuz Spacecraft at Space Station – U.S. Spacewalk Postponed

Space Station Astronauts Study Foams, Fires, and Liquids – Test New Toilet

Revolutionary Sepsis Treatment Moves to Next Phase of Human Trials

Be the first to comment on "three years later, the search for life on mars continues", leave a comment cancel reply.

Email address is optional. If provided, your email will not be published or shared.

Save my name, email, and website in this browser for the next time I comment.

Articles on Life on Mars

Displaying 1 - 20 of 42 articles.

NASA’s search for life on Mars: a rocky road for its rovers, a long slog for scientists – and back on Earth, a battle of the budget

Amy J. Williams , University of Florida

For All Mankind’s Happy Valley: why a Martian city could well extend below the surface

Elizabeth Stanway , University of Warwick

Could people breathe the air on Mars?

Phylindia Gant , University of Florida and Amy J. Williams , University of Florida

As the Perseverance rover lands on Mars, there’s a lot we already know about the red planet from meteorites found on Earth

James Scott , University of Otago

Perseverance Mars rover: how to prove whether there’s life on the red planet

Samantha Rolfe , University of Hertfordshire

Mars: Perseverance rover set for nail-biting landing – here’s the rocket science

Andrew Coates , UCL

As new probes reach Mars, here’s what we know so far from trips to the red planet

Tanya Hill , Museums Victoria Research Institute

How to get people from Earth to Mars and safely back again

Chris James , The University of Queensland

Mars: mounting evidence for subglacial lakes, but could they really host life?

David Rothery , The Open University

Perseverance: the Mars rover searching for ancient life, and the Aussie scientists who helped build it

David Flannery , Queensland University of Technology

NASA’s big move to search for life on Mars – and to bring rocks home

Briony Horgan , Purdue University and Melissa Rice , Western Washington University

Meteorites from Mars contain clues about the red planet’s geology

Arya Udry , University of Nevada, Las Vegas

Spotting alien life – how ‘microfossils’ can fool scientists

Alexander Brasier , University of Aberdeen

Tiny specks in space could be the key to finding martian life

Andrew Tomkins , Monash University

Tardigrades: we’re now polluting the moon with near indestructible little creatures

Monica Grady , The Open University

Why the idea of alien life now seems inevitable and possibly imminent

Cathal D. O'Connell , The University of Melbourne

Our long fascination with the journey to Mars

Paulo de Souza , CSIRO

Colonizing Mars means contaminating Mars – and never knowing for sure if it had its own native life

David Weintraub , Vanderbilt University

Sorry Elon Musk, but it’s now clear that colonising Mars is unlikely – and a bad idea

How to grow crops on Mars if we are to live on the red planet

Briardo Llorente , Macquarie University

Related Topics

• Extraterrestrial life
• Mars atmosphere
• Mars exploration
• Perseverance Rover
• Space exploration

Top contributors

Professor in Earth Sciences, Nanyang Technological University, Singapore, and Emeritus Professor of Mineral Physics, University of Cambridge

Professor, Griffith University

Professor of Physics, Deputy Director (Solar System) at the Mullard Space Science Laboratory, UCL

Professor of Astronomy, Vanderbilt University

Professor of Planetary Geosciences, The Open University

Assistant Professor of Geology, University of Florida

Senior Lecturer in Environmental Science and Planetary Exploration, University of Stirling

Associate member of the Australian Centre for Astrobiology, UNSW Sydney

Senior Lecturer in Chemistry, University of Birmingham

Professor of Planetary and Space Sciences, The Open University

Professor (Astrophysics), University of Southern Queensland

Senior Curator (Astronomy), Museums Victoria and Honorary Fellow at University of Melbourne, Museums Victoria Research Institute

PhD Student in Geosciences, University of Arizona

Director, Space Science and Technology Centre, Curtin University

Professor of Planetary Science and Astrobiology, Birkbeck, University of London; Honorary Associate Professor, UCL

• X (Twitter)
• Unfollow topic Follow topic

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Astrobiology

Searching for Life on Mars Before It Is Too Late

Alberto g. fairén.

1 Centro de Astrobiología (CSIC-INTA), Madrid, Spain.

2 Department of Astronomy, Cornell University, Ithaca, New York.

Victor Parro

Dirk schulze-makuch.

3 Center of Astronomy and Astrophysics, Technical University Berlin, Berlin, Germany.

4 SETI Institute, Mountain View, California.

5 Department of Natural Resource Sciences, McGill University, Québec, Canada.

Decades of robotic exploration have confirmed that in the distant past, Mars was warmer and wetter and its surface was habitable. However, none of the spacecraft missions to Mars have included among their scientific objectives the exploration of Special Regions, those places on the planet that could be inhabited by extant martian life or where terrestrial microorganisms might replicate. A major reason for this is because of Planetary Protection constraints, which are implemented to protect Mars from terrestrial biological contamination. At the same time, plans are being drafted to send humans to Mars during the 2030 decade, both from international space agencies and the private sector. We argue here that these two parallel strategies for the exploration of Mars ( i.e. , delaying any efforts for the biological reconnaissance of Mars during the next two or three decades and then directly sending human missions to the planet) demand reconsideration because once an astronaut sets foot on Mars, Planetary Protection policies as we conceive them today will no longer be valid as human arrival will inevitably increase the introduction of terrestrial and organic contaminants and that could jeopardize the identification of indigenous martian life. In this study, we advocate for reassessment over the relationships between robotic searches, paying increased attention to proactive astrobiological investigation and sampling of areas more likely to host indigenous life, and fundamentally doing this in advance of manned missions. Key Words: Contamination—Earth Mars—Planetary Protection—Search for life (biosignatures). Astrobiology 17, 962–970.

1. Introduction

T he main reason that international space agencies adduce to continue investing billions of dollars in Mars exploration is its potential for life and astrobiology. We concur that the biological exploration of Mars would find little match among the major scientific objectives for upcoming decades. Unfortunately, with the exception of the two Viking landers in 1976, all other lander and rover missions to Mars have been in fact primarily geology focused, although they are often put forward as astrobiology missions. In this context, they have been quite successful in confirming that in the distant past, Mars was warmer and wetter and the surface was habitable (Squyres et al. , 2008 ; Arvidson et al. , 2014 ; Grotzinger et al. , 2014 ), but none of them carried true life detection instrumentation as Viking did, and when new missions are designed to incorporate a true life-searching payload, as for example, ESA's ExoMars Rover, they do not include among their objectives the exploration of the Special Regions, defined as the places on Mars where terrestrial microorganisms might replicate or could be inhabitable by extant martian life.

This paradox arises from the implementation of Planetary Protection policies ( Box 1 ). The United Nations Outer Space Treaty stipulates protection of targeted celestial bodies to prevent forward contamination to avoid their harmful contamination (United Nations Office for Disarmament Affairs, 2015 ), and the COSPAR Planetary Protection policy statement proclaims that the conduct of scientific investigations of possible extraterrestrial life forms, precursors, and remnants must not be jeopardized (Rummel et al. , 2014 ; NASA Planetary Protection Office, 2015 ; COSPAR, 2016 ). In general, these Planetary Protection constraints have been largely interpreted to be in place to protect Mars from terrestrial biological contamination, safeguarding a possible martian biosphere, and to protect scientific investigations—for the mission at hand and for future missions—thus assuring that future generations could eventually study martian microorganisms without concerns of a potential detection of microbes carried forward on our spacecraft today, resulting in false-positive results.

Box 1.  The Evolving Planetary Protection Policies

Planetary Protection requirements are not static. There has been a continuous historical development of views on Planetary Protection and its categories as applied to Mars, which have particularly changed considerably since the Viking missions. There have been also multiple international studies and deliberation on the matter of Planetary Protection categories and approaches since Viking, particularly between Viking and Pathfinder missions. Additional changes are required at this moment, particularly because of the needed interaction with the Mars manned mission community, as highlighted in this article.

Special Regions were not discovered and walled off overnight. Special Regions were first discussed at the 2002 COSPAR Workshop, then later in more detail by MEPAG in 2006, COSPAR in 2007, MEPAG in 2104, and in a comprehensive review by NRC-ESA in 2015. Collectively, these studies integrated the knowledge and opinions of a large community of astrobiologists from multiple disciplines as well as international policy contributors, who reviewed voluminous data about Planetary Protection categories, extremophiles, and Mars.

Bioburden reduction requirements have also changed over time, from pre- and post-Viking. Updates to Planetary Protection requirements have resulted from additional advances in understanding about microbes and microbiomes in general, cleanroom technologies, new nonculture methods of detecting microbes, increasing knowledge of extremophiles on Earth, and better understanding of martian environments over time. Like any regulatory standards and implementations, the Planetary Protection levels and enactment protocols are set based on consensus of scientific input and balances with other needs.

Although no areas on Mars are theoretically off-limits to exploration as long as the missions meet the applicable contamination constraints, the reality is that current Planetary Protection policies are based on such stringent microbial reduction efforts for a life-searching mission (Rummel et al. , 2014 ) that, in practice, they have become a cost-prohibitive benchmark (Fairén and Schulze-Makuch, 2013 ) that is barring the implementation of strategies to search for life in the Special Regions.

It could be argued that a future proper life detection mission would not necessarily face problems in the exploration of Special Regions because it would have already set cleanliness standards that exceed the level of today's requirements. However, in our opinion, that would be wishful thinking. The reality is that the restrictions go to the extreme such that if the current NASA's Curiosity or the upcoming NASA's Mars2020 and ESA's ExoMars rovers came close to a Special Region, they would not be allowed to use their considerable (costly and difficult-to-put-there) instrumentation to sample and analyze for potential biosignatures because they are not cleaned to appropriate levels.

The best example of this is Curiosity (Benardini et al. , 2014 ), which was recently forbidden (Witze, 2016 ) to attempt to sample and analyze readily accessible recurring slope lineae (RSLs, narrow streaks formed on the surface arguably as a result of contemporary water activity, see Ojha et al. , 2015 ; Edwards and Piqueux, 2016 ), where the instruments onboard would have been able at least to test whether they contained briny liquid water; as a result, we will have to put together another multibillion dollar mission (with a 40% chance of landing successfully, see the latest Schiaparelli attempt) to essentially do what Curiosity could do presently in Gale Crater. NASA's Mars2020, which will introduce a drill to collect core samples of rocks and soils to search for signs of past microbial life (NASA Mars2020 mission overview), has likewise been directly required to avoid landing in Special Regions because it also will not be cleaned to appropriate levels.

The case of ExoMars is particularly dramatic as the first priority of the rover is to search for signs of past and present life on Mars (ESA's Scientific objectives of the ExoMars Rover, 2016 ); however, it has been explicitly banned to go to Special Regions because it will not comply with the minimum cleanliness requirements. As a consequence, the billion-dollar life-seeking mission ExoMars will be allowed to search for life everywhere on Mars, except in the very places where we suspect that life may exist. This incongruous situation has been stagnant for a long time and has delayed, sine die , a real quest for life on Mars.

However, now there is a game changer: after years of timid insinuations, NASA is, for the first time, seriously planning to send humans to Mars after 2030 (First Landing Site/Exploration Zone Workshop for Human Missions to the Surface of Mars, 2015 ; Obama, 2016 ; National Aeronautics and Space Administration Transition Authorization Act, 2017 ), including chartering a previous planning study to support martian water in situ resource utilization for eventual human missions (MEPAG, 2016 ). In addition, given the rapid advances in space flight technologies by other national space programs as well as within the private sector, it is not out of the realm of possibilities that other stakeholders may precede NASA in completing human missions to Mars (Musk, 2017 ), and the moment that an astronaut sets foot on Mars, Planetary Protection policies as we conceive them today will no longer be valid as microbial contamination from the human visitors will be unavoidable (McKay, 2009 ; Siefert, 2012 ); humans will increase not only the number (a human being is a collection of roughly 70 trillions of cells and bacteria; however, microbial invasion is not simply a matter of numbers) but also most importantly the diversity of microorganisms flying to Mars.

In addition, those microorganisms associated with the hardware will never be removed, which, along with the hardware, will be traveling anyway. All this microbial diversity would potentially leak out of a spacecraft or habitat module or waste deposit, and some of the organisms could end up in Special Regions because of transport by wind. In addition, in situ resource utilization, with the aim of extracting and processing martian resources to obtain life support consumables and propellants, will enormously raise the chances of forward contamination, especially during soil processing to extract liquid water.

The list of knowledge gaps that we need to address to begin to understand the actual contamination risks posed by a manned mission to Mars is challenging (NASA Workshop on Planetary Protection Knowledge Gaps for Human Extraterrestrial Missions, 2015 ; NASA Policy on Planetary Protection requirements for human extraterrestrial missions, 2016 ; National Academies, 2016). Therefore, the current strategy for the exploration of Mars, in practice, delays any efforts for the biological reconnaissance of Mars during the next two or three decades due to Planetary Protection concerns, but then, to subsequently send human missions directly to the planet would seem an unfortunate approach that without doubt would tremendously complicate our quest for indigenous life on Mars in the future.

We argue that the space science community should explore Mars thoroughly from a biological point of view over the next 10 to 20 years. To do so, we recommend that Planetary Protection restrictions are substantially relaxed to facilitate our robots and dedicated instruments to access and investigate the Special Regions. We argue that the benefits of this approach would offer significantly more with regard to planetary science research than any possible detriments from it by (1) facilitating discussion as to whether forward biological contamination of the surface of Mars by robots is so unlikely that the current stringent Planetary Protection policies deserve a serious rethinking and (2) acknowledging that we have the capability to distinguish a martian microorganism from that which is terrestrial when searching for life on Mars. We recommend this urgent and sharp turn of direction in Mars exploration because the alternative of remaining passive while waiting to see astronaut footprints on the red martian soil will very soon close off options for the future biological reconnaissance of Mars, putting us at a point of no return.

2. The Unlikely Contamination of Mars

We know that microbial life has already been transferred from Earth to Mars on more than one occasion, either naturally through impact events or through partially or nonsterilized spacecraft that have landed or crashed on Mars during the last five decades. Therefore, if Earth microorganisms can, in fact, survive and create active microbial ecosystems on present-day Mars, we can presume that they are already there; on the other hand, if Earth life cannot survive and most importantly reproduce on Mars today, our concerns about forward contamination of Mars with terrestrial organisms are unwarranted (Fairén and Schulze-Makuch, 2013 ).

The survival of Earth microorganisms on the surface and shallow subsurface of Mars is very unlikely (Pavlov et al. , 2002 ; Nicholson et al. , 2009 ; Khodadad et al. , 2017 ). We have been sending dirty spacecrafts to Mars since the Viking missions in 1976, yet compliant with the bioburden requirements based on scientifically accepted standards and protocols. Even the cleanest of missions carried hundreds of thousands of microbial stowaways, simply because we do not know how to completely sterilize our probes ( e.g. , Viking-level dry heat microbial reduction is often incorrectly termed as sterilization, when it is not, see Nicholson et al. , 2009 ).

In addition, unfortunately, the organisms that survived our cleaning procedures are actually the most hardy ones because they are more resistant to some of the same stresses that they are later exposed to on the surface of Mars ( e.g. , UV irradiation, plasma, oxidizing chemicals such as vapor hydrogen peroxide, and heat microbial reduction); therefore, we suggest that future research may show that current cleaning protocols are essentially conducting an artificial selection experiment, with the result that we carry on our spacecrafts only those microorganisms that may have a chance to survive on Mars—the others would be of no concern anyway—putting into question the whole cleaning procedure.

However, the surface of Mars has been, and still is, methodically sterilized with a broad radiation spectrum, extreme cold and dryness, and an inhospitable surface soil chemistry in the form of highly reactive oxidizing agents that essentially destroy most organic molecules (Nicholson et al. , 2009 ; Freissinet et al. , 2015 ; Khodadad et al. , 2017 ). It is true that multitudes of extremophile microbiology studies on Earth have demonstrated the extraordinary capacity of terrestrial microorganisms to create active microbial ecosystems in a variety of extreme terrestrial environments on Earth. In addition, numerous studies have shown the survivability of Earth organisms in Mars simulation chamber experiments up to months in artificial martian surface regolith ( e.g. , de Vera et al. , 2013 ; Smith et al. , 2017 ). However, the only report to date that hints of potential microbial growth under martian surface conditions demonstrated reproduction of Siberian Carnobacterium isolates under cold, low-pressure, and anoxic conditions (Nicholson et al. , 2013 ), although this assay was conducted in a rich growth medium that would never occur in martian surface soils.

Therefore, there is still no convincing report that clearly demonstrates how terrestrial microorganisms would survive and, crucially, be able to reproduce and form active microbial communities on the surface of Mars. If we were to stage a mission to Mars to investigate one of our non- or partially sterilized previous landers/rovers and reexamine it for life, we would anticipate that the outside of the spacecraft would be sterile due to several years of exposure to the surface environment of Mars, much more so compared with when the spacecraft left Earth (eventually, microbes inside the metal spacecraft will be killed by cosmic rays too, but that will take much longer than a few years).

Some recent investigations support the unlikely survival of earthlings on Mars. First, a motorized expedition was recently conducted in the Arctic to gain experience about future road trips on Mars (Schuerger and Lee, 2015 ). Along the way, samples of grit and snow were collected from inside and outside the vehicles to investigate whether (and the extent to which) microbes transported by the vehicles and crew might have found their way onto the surrounding pristine snow surface outside the vehicle. The results strongly indicate that in an environment immensely less harsh for terrestrial microbes than Mars, forward contamination was extremely limited to nonexistent.

Second, we have just learned that in an upper Antarctic Dry Valley near surface soils, where the ice in permafrost originates from vapor deposition rather than liquid water (similar to martian near-surface permafrost environments), microbial activity and survival are strictly limited because of the combination of severe cold, aridity, and oligotrophy (Goordial et al. , 2016 ). If soils in the upper Dry Valleys are potentially uninhabitable, even when they are continuously seeded with allochthonous organisms through aeolian deposition, then it is difficult to envision how Mars surface environments could ever support active microbial ecosystems, resulting from a handful of terrestrial microorganisms hitchhiking their way to Mars, because martian surface permafrost environments are much colder, drier, and older; receive much more radiation; and receive much less input (if any) of organic C, N, P, or allochthonous organisms than the upper Dry Valleys.

All the previous arguments have been tested, and we have strong evidence to claim that biological contamination has not occurred at global scales on the surface of Mars; the Curiosity rover is well equipped to identify organic compounds and still is having a very difficult time finding some (Freissinet et al. , 2015 ). Hence, if any terrestrial hitchhikers survived the journey to Mars and are still alive on the surface of the planet, they would be hiding within or around our shipwrecks and not planning field trips. Factoring in the potential natural transfer of microbes through meteorites, this argument can be extended back for millions or even billions of years. Therefore, even if terrestrial microorganisms were transported to Mars in one or several occasions during millions or billions of years, it is highly unlikely that there is a global biosphere derived from Earth organisms on the surface of Mars today, so the contamination (if any) has been very limited in space and time (McKay, 2009 ).

3. Recognizing the Martians

A different question would be the possibility of false positives, that is, any potential microbial hitchhikers on our spacecrafts could be mistaken for martian life. Should this really be a concern? We think it should not because molecular biology has advanced considerably in the last decades, and new methods in laboratory analysis make false-positive results far less likely. As such, if we find microorganisms on Mars by detecting their molecular markers (proteins, pigments, polysaccharides, and nucleic acids), we should be able to extract and sequence their genetic material to investigate their origin ( in situ and/or analyzing returned samples). Indeed, we only consider here the case that the martians are biochemically similar enough to Earth life that such mistakes could be a concern; if the martians have a different system to store and transmit their genetic information, then by definition, there will be no chance of mistakes in the identification (McKay, 2008 ). The arguments hereafter are more speculative as our intention is to open new avenues for this debate.

The DNA/RNA sequence is as specific as a personal passport and could reveal the roots and origin of the organisms. As sequencing complete genomes would prove problematic, and the existing databases are not yet large enough, 16S/18S ribosomal RNA sequencing will possibly be the better choice. If it is just contamination, multiple organisms should be found all very closely related to others ( i.e. , the same level of similarity typically identified when new Earth isolates are sequenced) in the database. This way, we may be able to map potential microbes found on Mars onto the universal tree of life and identify them. We do this routinely in our laboratories, and we are able to separately map very similar strains in different positions on the tree of life. As it is expected that the RNA/DNA sequence of any potential martian microorganisms will be significantly different from any organism on Earth, indigenous martian microbes might form a new kingdom or subkingdom at the very base of the Bacteria or Archaea branches of the universal tree of life. Furthermore, if panspermia occurred in the distant past, then 16S rRNA sequences from Mars organisms would consistently map to various subgroups on the tree of Earth life, but never to specific modern organisms. Depending on the level that this occurs (genus, order), the data would supply information on when the transport had occurred.

As an analog to Earth investigations, hundreds of new types of microorganisms were recently found in understudied terrestrial environments and they ended up comprising more than 15% of all known groups of Bacteria and nine new groups of Archaea, representing tens of new phyla about which very little was previously known (Brown et al. , 2015 ; Castelle et al. , 2015 ) ( Fig. 1 ). These new phyla were found to occupy entire new branches on the tree of life (Hug et al. , 2016 ).

The new groups of Bacteria and Archaea discovered in 2015 (CPR and DPANN, respectively) greatly expand the known and characterized phyla in a more and more complex tree of life, in which entire new branches are still being identified. These new advances show that we will be knowledgeable enough as to know where to distinctly map in the tree of life potential microorganisms found on Mars. (Image courtesy J. Banfield). CPR, Candidate Phyla Radiation; DPANN, Diapherotrites, Parvarchaeota, Aenigmarchaeota, Nanohaloarchaeota, and Nanoarchaeota.

Another example that demonstrates our ability to identify and trace novel organisms occurred during the 2013 outbreak of the bacterium Xylella fastidiosa in olive trees in Italy; microbiologists traced the particular strain of Xylella involved in the Italian outbreak as endemic in Costa Rica, the single place in the World where the strain was previously identified, and determined that the disease arrived in Italy with ornamental plants imported from Costa Rica (Abbott, 2015 ). Since we know how to attain such a high level of specificity in identifying the origin of terrestrial organisms, we may be able to identify and trace Earth life forms transported to Mars because they would be genetically much more separated from potential martian microorganisms.

The differences between martian and terrestrial organisms may eventually go beyond biochemistry, including their very cellular structure. If we find Earth-like life on Mars, having originated on Mars or having been transferred from Earth billions of years ago, this martian biosphere would have been exposed to the geological and environmental evolution of Mars, which was extremely different from that of Earth at least during the last 3 billion years. As a consequence, the evolutionary traits of these martians would be expected to be very different from indigenous Earth organisms.

For example, possibly some of the great events in Earth's life evolution, such as the endosymbiotic inception of the mitochondria and chloroplast from bacterial precursors, may never have occurred on Mars and hence only prokaryotes might have proliferated and evolved. In addition, bearing in mind that eukaryotes did not appear on Earth until ∼2 Gyr ago (Rasmussen et al. , 2008 ) and multicellular life until ∼1.5 Gyr ago (Zhu et al. , 2016 ), and considering that Mars has been a very cold and dry planet since at least 3 Gyr ago ( e.g. , Fairén, 2010 ), the replication rate and hence the evolutionary pace of any possible martian biota may have been very slow, and therefore eukaryotic organisms might not exist on Mars.

Terrestrial eukaryotes would have had infrequent transport to Mars as they appeared in a time with already reduced rock interchange between the planets; however, more importantly, those that were transported to Mars would have found there an extremely hostile environment totally different than their home planet. As a result, it is possible that only primitive life forms succeeded on Mars, such as lithoautotrophs, heterotrophic bacteria, and cyanobacteria, with neither relation to more modern terrestrial life forms nor horizontal genetic exchange with Earth's biosphere. A divergent evolution of biospheres on Earth and Mars may have the result that simple morphological and structural analyses would reveal noticeable differences between the martian and terrestrial microbiota ( Fig. 2 ).

Major evolutionary events of life on Earth represented together with the possible trajectory of a hypothetical martian biosphere. The origin of life could have occurred on Earth, on Mars, or on both planets, and then transferred from one to the other. On Earth, life gained a foothold early on and started to diversify (represented by the fat cone), driven by genetic interchange through promiscuous horizontal gene transfer (represented by the lines in the cone), and to transform the planet. The possible biological history of Mars is totally unknown (represented by the hypothetical thinner and blurred cone), maybe including scarce horizontal gene transfer events, resulting in smaller phylogenetic groups. The yellow arrows represent possible natural transfer of microbes from Earth to Mars through meteorites, a common event throughout the entire history of the Solar System. Today, the concern seems to be the possible presence of hitchhikers onboard our spacecrafts. LHB = Late Heavy Bombardment.

Using the same reasoning the other way around, if we identify life on Mars and it turns out to be genetically and biochemically very similar or identical to Earth life, then we can reasonably presume that we have caught our hitchhikers from Earth under the microscope. It is biologically and evolutionarily difficult to suggest that indigenous (or very early transported from Earth) martian life would be genetically and structurally so similar to modern Earth life that we would risk making wrong identifications. In addition, RNA/DNA analyses will be the perfect tool with which to identify the origin of potential organisms found on Mars. Furthermore, if putative martian organisms are found with no relative in the universal tree of life, then it would be regarded as likely martian, when it might just be related to members of a not yet discovered branch in the tree of Earth Life. However, since we would typically be looking at populations, finding a single organism in a population with no relatives could be explained as just a not yet described Earth organism.

It is true that RNA/DNA sequencing of martian samples would be challenging. Assuming the hypothetical case that some terrestrial cells transported by spacecrafts were able to survive and reproduce on Mars, their growth rate and generation time (the time required to double the number of cells in a microbial population) at freezing or nearly freezing temperatures (ambient conditions on Mars) would be extremely slow. For example, Planococcus halocryophilus , a permafrost bacterium with the coldest growth temperatures yet reported, was capable of doubling in ∼40 days at −15°C (Mykytczuk et al. , 2013 ); however, this assay was performed in a rich growth medium under optimal laboratory conditions, which would likely be much greater than would be found under ambient permafrost conditions.

A more realistic example would be the generation time of 2.5 years for bacteria exposed to temporal freeze–thaw cycles in the permanent ice covers of Antarctic lakes (Fritsen and Priscu, 1998 ). Assuming such an optimal environmental situation for Mars, a contamination of 100 metabolically active cells would require 50 years to produce a cell density of about 5000 cells/g in a square kilometer. This is in the threshold of many life detection systems, but enough to recover RNA/DNA in a sample return mission or to amplify the nucleic acids with polymerase chain reaction (PCR) techniques both in situ and back on Earth.

Furthermore, we have an excellent control with which to monitor the potential contamination of Mars: sequencing the microbes found in the clean spacecraft assembly rooms (Moissl-Eichinger et al. 2012 ; Checinska et al. , 2015 ; van Heereveld et al. , 2016 ). Any sequence identical or highly similar to those found on a martian sample would indicate very likely contamination and should be discarded as being indigenous to Mars.

All the facts described above strongly suggest that if we ever find microorganisms on Mars, we will be knowledgeable enough to distinguish martian (exobiota) from terrestrial (contamination) life. That of course applies only for a short time span in the future, while the terrestrial biological contamination of Mars (if any) remains contained (close to our spacecraft) and known (present in our clean rooms) and therefore manageable. Human missions will change the name of that game forever.

4. A New Road Map for Mars Exploration in the 21st Century

Following the heritage of the Viking landers (the only true life detection mission to Mars so far), we urge resumption of a dedicated astrobiological policy such that we invest the adequate amount of resources and put them in the right place in advance of human missions. It is imperative that the Mars astrobiological and manned mission communities work closer together on the path forward, finding collaborative solutions for shared problems and including in the conversation scientists, managers, and policy makers. We enthusiastically support any efforts directed to the human exploration of Mars and so the alternative of halting the advance of manned missions would not be a solution for us. Therefore, if we, the Mars community, are truly committed to determine whether life ever existed or still exists on Mars, we propose here a twofold change of strategy.

First, we advocate allowing immediate access to the Special Regions for vehicles with the cleanliness level of Curiosity, Mars2020, or ExoMars. For this, it would be necessary to reevaluate the current Planetary Protection restrictions and make sure they are properly adapted for the new space age we are entering, particularly distinguishing clearly between spacecraft cleanliness for biological reconnaissance and spacecraft cleanliness for planetary protection. This will reduce the likelihood that spacecraft cleanliness issues create conflicts between planetary protection efforts and science objectives, abiding to the principle that Planetary Protection policies should enable the exploration of Mars and not prohibit it (COSPAR Panel on Planetary Protection, 2017 ).

These proposed changes would require that COSPAR update the rules governing the robotic exploration of Mars at its next meeting in 2018, and the Outer Space Treaty should be amended as well. As immediate prospective go-to places, we particularly recommend analyzing potential transient liquid aqueous solutions and water ice, such as those recently identified in (1) the RSL (Ojha et al. , 2015 ); (2) the nighttime ephemeral brines formed in the shallow subsurface by absorbing atmospheric water vapor through deliquescence (Martín-Torres et al. , 2015 ); and (3) the shallow subsurface water ice at mid-high latitudes, where SHARAD radar data suggest that large layers, decameters thick, would enclose volumes of 10 4 km 3 of water (Bramson et al. , 2015 ; Stuurman et al. , 2016 ).

Second, we urge that our existing laboratory robotic technology is made flight ready in the search for biochemical evidence of life (McKay et al. , 2013 ; Schulze-Makuch et al. , 2013 ), and in particular, we advocate the development of robotic nucleic acid sequencing instrumentations for future in situ detection and/or sample return (Carr et al. , 2013 ). We will need parallel analyses for complex and polymeric sugars, lipids, peptides, and nucleic acids, as well as their building blocks such as sugars, nucleobases, and amino acids, so we will no longer be concerned about possible false-positive life detection. Robotic microscopes with very high resolution to analyze samples could also help to identify different cellular architectures.

The immediate ( i.e. , in less than 10 years) implementation of this new strategy outlined here is vital: before any human mission lands on Mars and exposes the planet to an unprecedented and very likely irreversible level of terrestrial bioburden, we should determine with well-designed life detection experiments whether any indigenous life exists on Mars, at least close to the anticipated human landing site and especially where we suspect that life might thrive (at the Special Regions nearby). We urge the prompt adoption of a proactive and comprehensive astrobiological strategy to find extant martian life before the onset of human missions, as opposed to continuing our sending more and more robotic geologists to Mars' sites where we do not expect the presence of life and, all the while, delay the biological exploration of the planet.

What we highlight here is a problem of timing: if we had still 50 or 70 years with no forecasted human presence on Mars ahead of us, we could sympathize with more conservative approaches for searching for extant martian life, but manned missions are already planned and budgeted for less than 20 years from today. It is very likely that our children or grandchildren (the Mars generation; Obama, 2016 ) will see astronaut footprints on the red sands of Mars, and at that moment, it will be much too late to straightforwardly identify the nature of true indigenous martians. This would be a lamentable loss for science because the main goal of Mars exploration should be to try and find life on Mars, understand the biochemical nature of martian life, and compare it with terrestrial life. Any scientifically rigorous search for life and understanding of its nature on Mars must address the question of whether it is a separate genesis or shares a common ancestor with life on Earth. Finding signs of life on Mars should not be the end or the mission accomplished coda for decades of planetary investigation; on the contrary, it will be just the beginning of a new age for science, culture, philosophy, and exploration.

Abbreviations Used

Acknowledgments.

The research leading to these results is a contribution from the Project icyMARS, funded by the European Research Council, Starting Grant no 307496. This research received funding from the Spanish Ministry of Economy and Competitiveness (MINECO) grant no ESP2015-69540-R. D.S.-M. was supported by the ERC Advanced Grant “Home” (339231). The manuscript was improved by constructive comments from two anonymous reviewers. The guidance provided by Chris McKay, Senior Editor of the Forum Section of Astrobiology, is deeply appreciated.

Author Disclosure Statement

No competing financial interests exist.

• Abbott A. (2015) Italian scientists under investigation after olive-tree deaths . Nature , doi: 10.1038/nature.2015.19078 [ CrossRef ] [ Google Scholar ]
• Arvidson R.E., Squyres S.W., Bell J.F., III, Catalano J.G., Clark B.C., Crumpler L.S., de Souza P.A., Jr., Fairén A.G., Farrand W.H., Fox V.K., Gellert R., Ghosh A., Golombek M.P., Grotzinger J.P., Guinness E.A., Herkenhoff K.E., Jolliff B.L., Knoll A.H., Li R., McLennan S.M., Ming D.W., Mittlefehldt D.W., Moore J.M., Morris R.V., Murchie S.L., Parker T.J., Paulsen G., Rice J.W., Ruff S.W., Smith M.D., and Wolff M.J. (2014) Ancient aqueous environments at Endeavour Crater, Mars . Science 343 :1248097. [ PubMed ] [ Google Scholar ]
• Benardini J.N., III, La Duc M.T., Beaudet R.A., and Koukol R. (2014) Implementing planetary protection measures on the Mars Science Laboratory . Astrobiology 14 :27–32 [ PubMed ] [ Google Scholar ]
• Bramson A.M., Byrne S., Putzig N.E., Sutton S., Plaut J.J., Brothers T.C., and Holt J.W. (2015) Widespread excess ice in Arcadia Planitia, Mars, Geophys . Res Lett 42 :6566–6574 [ Google Scholar ]
• Brown C.T., Hug L.A., Thomas B.C., Sharon I., Castelle C.J., Singh A., Wilkins M.J., Wrighton K.C., Williams K.H., and Banfield J.F. (2015) Unusual biology across a group comprising more than 15% of domain Bacteria . Nature 523 :208–211 [ PubMed ] [ Google Scholar ]
• Carr C.E., Rowedder H., Lui C.S., Zlatkovsky I., Papalias C.W., Bolander J., Myers J.W., Bustillo J., Rothberg J.M., Zuber M.T., and Ruvkun G. (2013) Radiation resistance of sequencing chips for in situ life detection . Astrobiology 13 :560–569 [ PubMed ] [ Google Scholar ]
• Castelle C.J., Wrighton K.C., Thomas B.C., Hug L.A., Brown C.T., Wilkins M.J., Frischkorn K.R., Tringe S.G., Singh A., Markillie L.M., Taylor R.C., Williams K.H., and Banfield J.F. (2015) Genomic expansion of domain Archaea highlights roles for organisms from new phyla in anaerobic carbon cycling . Curr Biol 25 :690–701 [ PubMed ] [ Google Scholar ]
• Checinska A., Probst A.J., Vaishampayan P., White J.R., Kumar D., Stepanov V.G., et al. (2015) Microbiomes of the dust particles collected from the International Space Station and Spacecraft Assembly Facilities . Microbiome 3 , 50. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• COSPAR. (2016) Assembly . Available online at www.cospar-assembly.org/
• COSPAR Panel on Planetary Protection. (2017) Proposed new terms of reference for the COSPAR Panel on Planetary Protection . COSPAR, Paris, France, p 1 Approved by COSPAR Bureau on March 22, 2017 [ Google Scholar ]
• de Vera J.-P., Schulze-Makuch D., Khan A., Lorek A., Koncz A., Ott S., Möhlmann D., and Spohn T. (2013) Adaptation of the lichen Pleopsidium chlorophanum to Martian surface conditions within 35 days . Planet Space Sci 198 :182–190 [ Google Scholar ]
• Edwards C.S., and Piqueux S. (2016) The water content of recurring slope lineae on Mars, Geophys . Res Lett 43 :8912–8919 [ Google Scholar ]
• ESA's Scientific objectives of the ExoMars rover. (2016) Available online at http://exploration.esa.int/mars/45082-rover-scientific-objectives/
• Fairén A.G. (2010) A cold and wet Mars . Icarus 208 :165–175 [ Google Scholar ]
• Fairén A.G., and Schulze-Makuch D. (2013) The overprotection of Mars . Nat Geosci 6 :510–511 [ Google Scholar ]
• First Landing Site/Exploration Zone Workshop for Human Missions to the Surface of Mars, Houston, Texas, October27–30 (2015) Available online at https://www.hou.usra.edu/meetings/explorationzone2015/ [ Google Scholar ]
• Freissinet C., et al. (2015) Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars . J Geophys Res Planets 120 :495–514 [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Fritsen C.H., and Priscu J.C. (1998) Cyanobacterial assemblages in permanent ice covers on antarctic lakes: distribution, growth rate, and temperature response of photosynthesis . J Phycol 34 :587–597 [ Google Scholar ]
• Goordial J., Davila A., Lacelle D., Pollard W., Marinova M.M., Greer C.W., DiRuggiero J., McKay C.P., and Whyte L.G. (2016) Nearing the cold-arid limits of microbial life in permafrost of an upper dry valley, Antarctica . ISME J 10 :1613–1624 [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Grotzinger J.P., Sumner D.Y., Kah L.C., Stack K., Gupta S., Edgar L., Rubin D., Lewis K., Schieber J., Mangold N., Milliken R., Conrad P.G., DesMarais D., Farmer J., Siebach K., Calef F., Hurowitz J., McLennan S.M., Ming D., Vaniman D., Crisp J., Vasavada A., Edgett K.S., Malin M., Blake D., Gellert R., Mahaffy P., Wiens R.C., Maurice S., Grant J.A., Wilson S., Anderson R.C., Beegle L., Arvidson R., Hallet B., Sletten R.S., Rice M., Bell J., Griffes J., Ehlmann B., Anderson R.B., Bristow T.F., Dietrich W.E., Dromart G., Eigenbrode J., Fraeman A., Hardgrove C., Herkenhoff K., Jandura L., Kocurek G., Lee S., Leshin L.A., Leveille R., Limonadi D., Maki J., McCloskey S., Meyer M., Minitti M., Newsom H., Oehler D., Okon A., Palucis M., Parker T., Rowland S., Schmidt M., Squyres S., Steele A., Stolper E., Summons R., Treiman A., Williams R., and Yingst A. (2014) A habitable fluvio-lacustrine environment at Yellowknife Bay, Gale Crater, Mars . Science 343 :1242777. [ PubMed ] [ Google Scholar ]
• Hug L.A., Baker B.J., Anantharaman K., Brown C.T., Probst A.J., Castelle C.J., Butterfield C.N., Hernsdorf A.W., Amano Y., Ise K., Suzuki Y., Dudek N., Relman D.A., Finstad K.M., Amundson R., Thomas B.C., and Banfield J.F. (2016) A new view of the tree of life . Nat Microbiol 1 :16048. [ PubMed ] [ Google Scholar ]
• Khodadad C.L., Wong G.M., James L.M., Thakrar P.J., Lane M.A., Catechis J.A., and Smith D.J. (2017) Stratosphere conditions inactivate bacterial endospores from a Mars spacecraft assembly facility . Astrobiology 17 :337–350 [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Martín-Torres F.J., et al. (2015) Transient liquid water and water activity at Gale crater on Mars . Nat Geosci 8 :357–361 [ Google Scholar ]
• McKay C.P. (2008) An approach to searching for life on Mars, Europa, and Enceladus . Space Sci Rev 135 :49 [ Google Scholar ]
• McKay C.P. (2009) Biologically reversible exploration . Science 323 :718. [ PubMed ] [ Google Scholar ]
• McKay C.P., Stoker C.R., Glass B.J., Davé A.I., Davila A.F., Heldmann J.L., Marinova M.M., Fairén A.G., Quinn R.C., Zacny K.A., Paulsen G., Smith P.H., Parro V., Andersen D.T., Hecht M.H., Lacelle D., and Pollard W.H. (2013) The Icebreaker life mission to Mars: a search for biomolecular evidence for life . Astrobiology 13 :334–353 [ PubMed ] [ Google Scholar ]
• MEPAG. (2016) ISRU for Eventual Human Missions . Available online at http://mepag.jpl.nasa.gov/goal.cfm?goal=3
• Moissl-Eichinger C., Rettberg P., and Pukall R. (2012) The first collection of spacecraft-associated microorganisms: a public source for extremotolerant microorganisms from spacecraft assembly clean rooms . Astrobiology 12 :1024–1034 [ PubMed ] [ Google Scholar ]
• Musk E. (2017) Making humans a multi-planetary species . New Space 5 :46–61 [ Google Scholar ]
• Mykytczuk N.C., Foote S.J., Southam G., Greer C.W., and Whyte L.G. (2013) Bacterial growth at −15°C; molecular insights from the permafrost bacterium Planococcus halocryophilus Or1 . ISME J 7 :1211–1226 [ PMC free article ] [ PubMed ] [ Google Scholar ]
• NASA Mars2020 Mission Overview. Available online at https://mars.nasa.gov/mars2020/mission/overview
• NASA Planetary Protection Office. (2015) Available online at http://planetaryprotection.nasa.gov/overview
• NASA Policy on Planetary Protection requirements for human extraterrestrial missions. (2016) NASA Policy Instruction NPI 8020.7, NPD 8020.7G
• NASA Workshop on Planetary Protection Knowledge Gaps for Human Extraterrestrial Missions. (2015) NASA Office of Planetary Protection & NASA Human Exploration and Operations . Available online at https://planetaryprotection.arc.nasa.gov/humanworkshop2015/
• National Academies of Sciences, Engineering, and Medicine. (2015) Review of the MEPAG Report on Mars Special Regions . Washington, DC: The National Academies Press; Available online at https://doi.org/10.17226/21816 [ Google Scholar ]
• National Aeronautics and Space Administration Transition Authorization Act. (2017) Available online at www.congress.gov/congressional-record/2017/03/07/house-section/article/H1553-1
• Nicholson W.L., Krivushin K., Gilichinsky D., and Schuerger A.C. (2013) Growth of Carnobacterium spp. from permafrost under low pressure, temperature, and anoxic atmosphere has implications for Earth microbes on Mars . Proc Natl Acad Sci U S A 110 :666–671 [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Nicholson W.L., Schuerger A.C., and Race M.S. (2009) Migrating microbes and planetary protection . Trends Microbiology 17 :389–392 [ PubMed ] [ Google Scholar ]
• Obama B. (2016) America will take the giant leap to Mars . CNN News . Available online at http://edition.cnn.com/2016/10/11/opinions/america-will-take-giant-leap-to-mars-barack-obama/index.html
• Ojha L., Wilhelm M.B., Murchie S.L., McEwen A.S., Wray J.J., Hanley J., Massé M., and Chojnacki M. (2015) Spectral evidence for hydrated salts in recurring slope lineae on Mars . Nat Geosci 8 :829–832 [ Google Scholar ]
• Pavlov A.K., Blinov A.V., and Konstantinov A.N. (2002) Sterilization of Martian surface by cosmic radiation . Planet Space Sci 50 :669–673 [ Google Scholar ]
• Rasmussen B., Fletcher I.R., Brocks J.J., and Kilburn M.R. (2008) Reassessing the first appearance of eukaryotes and cyanobacteria . Nature 455 :1101–1104 [ PubMed ] [ Google Scholar ]
• Rummel J.D., Beaty D.W., Jones M.A., Bakermans C., Barlow N.G., Boston P.J., Chevrier V.F., Clark B.C., de Vera J.-P.P., et al (2014) A new analysis of Mars ‘Special Regions’: findings of the second MEPAG Special Regions Science Analysis Group (SR-SAG2) . Astrobiology 14 :887–968 [ PubMed ] [ Google Scholar ]
• Schuerger A.C., and Lee P. (2015) Microbial ecology of a crewed rover traverse in the Arctic: low microbial dispersal and implications for planetary protection on human Mars missions . Astrobiology 15 :478–491 [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Schulze-Makuch D., Fairén A.G., and Davila A. (2013) Locally targeted ecosynthesis: a proactive in situ search for extant life on other worlds . Astrobiology 13 :674–678 [ PubMed ] [ Google Scholar ]
• Siefert J.L. (2012) Man and his spaceships . Mob Genet Elements 2 :272–278 [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Smith S.A., Benardini J.N., III, Anderl D., Ford M., Wear E., Schrader M., Schubert W., DeVeaux L., Paszczynski A., and Childers S.E. (2017) Identification and characterization of early mission phase microorganisms residing on the Mars Science Laboratory and assessment of their potential to survive Mars-like conditions . Astrobiology 17 :253–265 [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Squyres S.W., Arvidson R.E., Ruff S., Gellert R., Morris R.V., Ming D.W., Crumpler L., Farmer J.D., Des Marais D.J., Yen A., McLennan S.M., Calvin W., Bell J.F., III, Clark B.C., Wang A., McCoy T.J., Schmidt M.E., and de Souza P.A., Jr (2008) Detection of silica-rich deposits on Mars . Science 320 :1063–1067 [ PubMed ] [ Google Scholar ]
• Stuurman C.M., Osinski G.R., Holt J.W., Levy J.S., Brothers T.C., Kerrigan M., and Campbell B.A. (2016) SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars, Geophys . Res Lett 43 :9484–9491 [ Google Scholar ]
• United Nations Office for Disarmament Affairs. (2015) Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies , Article IX, version 2015, signed by almost all nation states, including all the current and aspiring space-faring nation states. Available online at http://disarmament.un.org/treaties/t/outer_space
• van Heereveld L., Merrison J., Nørnberg P., and Finster K. (2016) Assessment of the forward contamination risk of Mars by clean room isolates from space-craft assembly facilities through aeolian transport—a model study . Orig Life Evol Biosphl 47 :203–214 [ PubMed ] [ Google Scholar ]
• Witze A. (2016) Mars contamination fear could divert Curiosity rover . Available online at www.nature.com/news/mars-contamination-fear-could-divert-curiosity-rover-1.20544 [ PubMed ]
• Zhu S., Zhu M., Knoll A.H., Yin Z., Zhao F., Sun S., Qu Y., Shi M., and Liu H. (2016) Decimetre-scale multicellular eukaryotes from the 1.56-billion-year-old Gaoyuzhuang Formation in North China . Nat Commun 7 :11500. [ PMC free article ] [ PubMed ] [ Google Scholar ]

MIT Space Research Reaches to Mars and Beyond

“We have confirmed that Earth-based life can survive in hydrogen-rich atmospheres.” — Sara Seager, Class of 1941 Professor of Planetary Science, Physics, and Aeronautics and Astronautics

Is there another Earth out in the cosmos? Was there ever life on Mars? Do invisible particles hold the secret to the origins of the universe?

Such fundamental questions drive researchers across MIT as they investigate mysteries at the heart of existence, from subatomic particles to black holes. With broad support from MIT’s alumni and friends, researchers are learning more about unexplained phenomena such as fast radio bursts, tracing the geologic record back billions of years, and teaming with NASA to search for signs of life beyond our solar system.

This work is laying the groundwork for human travel to Mars, perhaps even interplanetary civilization, while going further than ever before to explain the world in which we live. Below are just a few examples of the ways in which MIT is reaching for the stars.

The MIT-led NASA mission TESS is monitoring more than 500,000 stars , searching for planets.

The Search for Signs of Life on Extrasolar Planets

MIT is leading NASA’s Transiting Exoplanet Survey Satellite (TESS) mission to investigate planetary systems circling nearby stars—pushing the field forward in the search for signs of life on extrasolar planets. Already TESS has discovered hundreds of new worlds that are among the nearest exoplanets known to date.

TESS is a NASA Astrophysics Explorer mission led and operated by MIT and managed by NASA’s Goddard Space Flight Center. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Center for Astrophysics | Harvard & Smithsonian; MIT’s Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes, and observatories worldwide are participants in the mission.

Explore more : → TESS Discovers Three New Planets Nearby, Including Temperate “Sub-Neptune” → TESS Team Is Awarded NASA’s Silver Achievement Medal

Investigating Unexplained Phenomena

Fast radio bursts are oddly bright flashes of light, registering in the radio band of the electromagnetic spectrum, that blaze for a few milliseconds before vanishing without a trace. Their origins are unknown. MIT researchers are exploring the astrophysics behind these events using a special radio telescope called CHIME (Canadian Hydrogen Intensity Mapping Experiment). Their goal is to pin down exactly what kind of exotic phenomena could generate such signals.

Explore more : → CHIME Telescope Detects More than 500 Mysterious Fast Radio Bursts in its First Year of Operation

Delving into Dark Matter

Astrophysicists at MIT have detected stars at the edge of Tucana II, an ultrafaint dwarf galaxy about 163,000 light years from Earth, a finding that suggests the galaxy hosts an extended halo of dark matter, a hypothetical type of matter thought to make up more than 85% of the universe. This discovery suggests that the very first galaxies were likely broader and more massive than previously thought.

Explore more : → Astronomers Detect Extended Dark Matter Halo Around Ancient Dwarf Galaxy

The Case for Life in a Hydrogen-Rich Atmosphere

MIT research indicates that microbes can survive and thrive in atmospheres dominated by hydrogen. This  work suggests simple forms of life might inhabit planets with environments vastly different from Earth, which has an atmosphere rich in nitrogen and oxygen.

Explore more : → Study: Life Might Survive, and Thrive, in a Hydrogen World

A Look at Ancient Mars

MIT geobiology research centers on the processes by which ancient rock formations were produced. In collaboration with NASA, which is collecting samples from Mars with its Perseverance ​Rover, researchers are hoping to discover what Mars might have been like in the past, and what life might be expected in those conditions.

The approximate age of the Jezero Crater on Mars, which MIT geobiologists are investigating for signs of life, is 4 billion years .

Explore more : → And Back: Mechanisms for Bringing Mars to Earth

Tiny Particles and the Big Bang

Particle physicists at MIT use experiments to detect minute particles in the hopes of answering important questions about the Big Bang and other cosmic phenomena. The ABRACADABRA (A Broadband/Resonant Approach to Cosmic Axion Detection with an Amplifying B-field Ring Apparatus) experiment, for example, is designed to detect axions, a hypothetical particle that may be the primary constituent of dark matter.

Explore more : → Particle Physicist Lindley Winslow Seeks the Universe’s Smallest Particles for Answers to its Biggest Questions

This article was originally published in August 2021.

Explore Topics

With your support, we will build a better world.

More Stories

Curiosity Rover Science

Landing at Gale Crater, Mars Science Laboratory is assessing whether Mars ever had an environment capable of supporting microbial life. Determining past habitability on Mars gives NASA and the scientific community a better understanding of whether life could have existed on the Red Planet and, if it could have existed, an idea of where to look for it in the future.

Science Objectives

To contribute to the four Mars exploration science goals and meet its specific goal of determining Mars' habitability, Curiosity has the following science objectives:

Biological objectives

Geological and geochemical objectives, planetary process objectives, surface radiation objective.

1. Determine the nature and inventory of organic carbon compounds 2. Inventory the chemical building blocks of life (carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur) 3. Identify features that may represent the effects of biological processes

1. Investigate the chemical, isotopic, and mineralogical composition of the Martian surface and near-surface geological materials 2. Interpret the processes that have formed and modified rocks and soils

1. Assess long-timescale (i.e., 4-billion-year) atmospheric evolution processes 2. Determine present state, distribution, and cycling of water and carbon dioxide

Characterize the broad spectrum of surface radiation, including galactic cosmic radiation, solar proton events, and secondary neutrons

Science Highlights

With over a decade of exploration, Curiosity has unveiled the keys to some of science's most unanswered questions about Mars. Did Mars ever have the right environmental conditions to support small life forms called microbes? Early in its mission, Curiosity's scientific tools found chemical and mineral evidence of past habitable environments on Mars. It continues to explore the rock record from a time when Mars could have been home to microbial life.

Science Instruments

From cameras to environmental and atmospheric sensors, the Curiosity rover has a suite of state-of-the-art science instruments to achieve its goals.

Discover More Topics From NASA

James Webb Space Telescope

Perseverance Rover

Parker Solar Probe

Essay on Life on Mars for Students and Children

500 words essay on life on mars.

Mars is the fourth planet from the sun in our solar system. Also, it is the second smallest planet in our solar system. The possibility of life on mars has aroused the interest of scientists for many years. A major reason for this interest is due to the similarity and proximity of the planet to Earth. Mars certainly gives some indications of the possibility of life.

Possibilities of Life on Mars

In the past, Mars used to look quite similar to Earth. Billions of years ago, there were certainly similarities between Mars and Earth. Furthermore, scientists believe that Mars once had a huge ocean. This ocean, experts believe, covered more of the planet’s surface than Earth’s own oceans do so currently.

Moreover, Mars was much warmer in the past that it is currently. Most noteworthy, warm temperature and water are two major requirements for life to exist. So, there is a high probability that previously there was life on Mars.

Life on Earth can exist in the harshest of circumstances. Furthermore, life exists in the most extreme places on Earth. Moreover, life on Earth is available in the extremely hot and dry deserts. Also, life exists in the extremely cold Antarctica continent. Most noteworthy, this resilience of life gives plenty of hope about life on Mars.

There are some ingredients for life that already exist on Mars. Bio signatures refer to current and past life markers. Furthermore, scientists are scouring the surface for them. Moreover, there has been an emergence of a few promising leads. One notable example is the presence of methane in Mars’s atmosphere. Most noteworthy, scientists have no idea where the methane is coming from. Therefore, a possibility arises that methane presence is due to microbes existing deep below the planet’s surface.

One important point to note is that no scratching of Mars’s surface has taken place. Furthermore, a couple of inches of scratching has taken place until now. Scientists have undertaken analysis of small pinches of soil. There may also have been a failure to detect signs of life due to the use of faulty techniques. Most noteworthy, there may be “refugee life” deep below the planet’s surface.

Get the huge list of more than 500 Essay Topics and Ideas

Challenges to Life on Mars

First of all, almost all plants and animals cannot survive the conditions on the surface of Mars. This is due to the extremely harsh conditions on the surface of Mars.

Another major problem is the gravity of Mars. Most noteworthy, the gravity on Mars is 38% to that of Earth. Furthermore, low gravity can cause health problems like muscle loss and bone demineralization.

The climate of Mars poses another significant problem. The temperature at Mars is much colder than Earth. Most noteworthy, the mean surface temperatures of Mars range between −87 and −5 °C. Also, the coldest temperature on Earth has been −89.2 °C in Antarctica.

Mars suffers from a great scarcity of water. Most noteworthy, water discovered on Mars is less than that on Earth’s driest desert.

Other problems include the high penetration of harmful solar radiation due to the lack of ozone layer. Furthermore, global dust storms are common throughout Mars. Also, the soil of Mars is toxic due to the high concentration of chlorine.

To sum it up, life on Mars is a topic that has generated a lot of curiosity among scientists and experts. Furthermore, establishing life on Mars involves a lot of challenges. However, the hope and ambition for this purpose are well alive and present. Most noteworthy, humanity must make serious efforts for establishing life on Mars.

FAQs on Life on Mars

Q1 State any one possibility of life on Mars?

A1 One possibility of life on Mars is the resilience of life. Most noteworthy, life exists in the most extreme places on Earth.

Q2 State anyone challenge to life on Mars?

A2 One challenge to life on Mars is a great scarcity of water.

Customize your course in 30 seconds

Which class are you in.

• Travelling Essay
• Picnic Essay
• Our Country Essay
• My Parents Essay
• Essay on Favourite Personality
• Essay on Memorable Day of My Life
• Essay on Knowledge is Power
• Essay on Gurpurab
• Essay on My Favourite Season
• Essay on Types of Sports

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Download the App

“Is there life on Mars?” is a question people have asked for more than a century. But in order to finally get the answer, we have to know what to look for and where to go on the planet to look for evidence of past life. With the Perseverance rover set to land on Mars on February 18, 2021, we are finally in a position to know where to go, what to look for, and knowing whether there is, or ever was, life on the Red Planet.

Science fiction aside, we know that there were not ancient civilizations or a population of little green people on Mars. So, what sort of things do we need to look for to know whether there was ever life on Mars? Fortunately, a robust Mars exploration program, including orbiters, landers, and rovers, has enabled detailed mapping of the planet and constrained important information about the environment.

We now know that there were times in the ancient past on Mars when conditions were wetter and at least a little warmer than the fairly inhospitable conditions that are present today. And there were once habitable environments that existed on the surface. For example, the Curiosity rover has shown that more than three billion years ago, Gale crater was the location of a lake  that held water likely suitable for sustaining life. Armed with information about the conditions and chemical environments on the surface, the Perseverance rover is outfitted with a science payload of instruments finely tuned for extracting information related to any biosignatures that might be present and signal the occurrence of life .

Panoramic view of the interior and rim of Gale crater. Image generated from pictures captured by the Curiosity rover.

But where should we go on Mars to maximize the chances of accessing the rocks most likely to have held and preserve any evidence of past life? To get at that answer, I co-led a series of workshops attended by the Mars science community to consider various candidate landing sites and help determine which one had the highest potential for preserving evidence of past life. Using data from Mars orbiters coupled with more detailed information from landers and rovers, we started with around thirty candidate sites and narrowed the list over the course of four workshops and five years. Some sites were clearly less viable than others and were weeded out fairly quickly. But once the discussion focused on a couple of different types of potentially viable sites, the process became much tougher. In the end, the science community felt—and the Perseverance mission and NASA agreed—that Jezero crater was the best place to look for evidence of past life on Mars.

This image shows the remains of an ancient delta in Mars' Jezero Crater, which NASA's Perseverance Mars rover will explore for signs of fossilized microbial life. The image was taken by the High Resolution Stereo Camera aboard the ESA (European Space Agency) Mars Express orbiter. The European Space Operations Centre in Darmstadt, Germany, operates the ESA mission. The High Resolution Stereo Camera was developed by a group with leadership at the Freie Universitat Berlin.

What is so special about Jezero crater and where is it? Jezero crater is ~30 miles (~49 km) across, was formed by the impact of a large meteorite, and is located in the northern hemisphere of Mars (18.38°N 77.58°E) on the western margin of the ancient and much larger Isidis impact basin. But what makes it special relates to events that happened 3.5 billion years ago when water was more active on the surface of Mars than it is today. Ancient rivers on the western side of Jezero breached the crater rim and drained into the crater, forming a river delta and filling the crater with a lake. From the study of river deltas on the Earth, we know that they typically build outwards into lakes as sediment carried by the associated river enters the lake, slows down, and is deposited. As this process continues, the delta builds out over the top of lake beds and can bury and preserve delicate and subtle signatures of past life. These “biosignatures” are what Perseverance will be looking for when it lands on the floor of the crater and explores the ancient lake beds and nearby delta deposits.

Perseverance will use its instruments to look for signs of ancient life in the delta and lake deposits in Jezero crater and will hopefully allow us to finally answer the question of whether there was ever life on Mars. In addition, Perseverance will begin the process of collecting samples that could one day be returned to Earth. The importance of sample return cannot be overstated. Whether or not evidence of past life is found by Perseverance’s instruments, the legacy enabled by samples the rover collects will be the “scientific gift that keeps on giving”. Once returned to Earth by a future mission, these Mars samples can be subjected to more detailed analysis by a much wider set of instruments than can be carried by Perseverance . Moreover, sample archiving can preserve material for future analysis here on Earth by new and/or more detailed instruments that may not yet exist. So even if Perseverance does not find evidence of past life, it will collect samples that, once returned to Earth, could provide new insight into the evolution of Mars and whether there was ever life on the Red Planet.

We rely on the generous support of donors, sponsors, members, and other benefactors to share the history and impact of aviation and spaceflight, educate the public, and inspire future generations.  With your help, we can continue to preserve and safeguard the world’s most comprehensive collection of artifacts representing the great achievements of flight and space exploration.

• Get Involved
• Host an Event

Thank you. You have successfully signed up for our newsletter.

Error message, sorry, there was a problem. please ensure your details are valid and try again..

• Free Timed-Entry Passes Required
• Terms of Use

Astronomy Issues: Life on Mars Research Paper

Introduction, the surface of mars, the atmosphere, controversial issues about mars, the idea of transforming mars, the idea of preserving the planet, summary and conclusion.

Mars is a planet that is similar and closer to earth than other planets. The planet has soil and rocks on its surface, and it has some gases in the atmosphere. Earlier researches indicated that there was a possibility of having some water, which is an essential aspect of life. According to astronomical researches, Mars has a cold climate, and the length of days and nights in Mars have a pattern similar to the one on Earth.

Moreover, since the axial tilt of Mars is similar to Earth’s axial tilt, the two planets experience the same seasons. The mentioned findings cause much anxiety as scientists suspect that the planet may support life.

If the assumptions are true, it would be necessary to find out if there was some ancient life on Mars and the possibility of having life on Mars. The National Aeronautics and Space Administration agency (NASA) has done several aerospace types of research to find out if indeed the planet can support life. This paper will take a stringent analysis of the research findings to determine the possibility of life on Mars.

In 1864, some curious astronomers gazed at Mars through telescopes, and they perceived the surface of Mars to have some vegetation. However, a spacecraft was able to arrive on Mars a hundred years later, and interestingly, there was no vegetation on Mars. The land was bare, and there was no evidence of water or life. Since then, several robotic spacecraft have arrived on the planet, but none has proved that Mars has a sign of life.

The most interesting thing to note is the earth’s magnetic field that turns away dangerous radiation particles in the space. Mars has no magnetic field to turn away the dangerous radiations; therefore, the planet is hostile to any form of life (Space Place, 2014, para. 5). The magnetic shield protects the atmosphere from losing moisture; therefore, lack of it makes the planes susceptible to losing its atmospheric moisture to the solar wind.

Mars has less air than the earth does, and there is no evidence of water on the planet. In case there was water on the planet, it must have been too saline to support life. The scientific experiments facilitated by robotic spacecraft that arrived in Mars never revealed any sign of living microorganisms in the soil.

Indeed, the absence of living microorganisms in the soil is a clear indication of the absence of water on the red planet. NASA has also employed efforts to find out whether the soil particles might contain tiny fossils that would be a sign of ancient life on Mars. So far, the aerospace research reports have not found any feasible results indicating the presence of life in the cold desert.

The Red Planet’s surface temperatures lie between -143oc and +27oc, and indeed, these temperatures are considerably low. The most controversial fact about Mars is the thin atmospheric pressure that is about 1% of that on earth (Turner, 2004, p. 306).

The air is dry with no liquid water, and the ultraviolet radiations in the atmosphere cannot support life in any way. It is noteworthy that Mars’ polar caps have frozen carbon dioxide, which would thicken the atmosphere if released into the air through warming.

Interestingly, there is no rain on Mars, and the planet obtains less sunshine than the Earth due to its long distance from the sun. Although carbon dioxide that is necessary for photosynthesis is plenty on the Red Planet, it is almost impossible for the planet to support plant life because of the lack of light energy (Hunter, 2013, p. 22). In the absence of the plants, herbivorous cannot survive, and consequently, the carnivorous cannot survive on the Red Planet.

No one can tell the truth about the images that show large river channel networks on the Red Planet. Explorers are wondering if the layered sediments may imply that Mars had some flowing rivers in the past. There are assumptions that Mars was a warm and wet place, but for unknown reasons, everything dried up.

It is noteworthy that air and water are the most important aspects of life; interestingly, Mars cannot support liquid water because of its low temperatures. Secondly, the atmospheric pressure on Mars cannot allow the exchange of gases. While animals need high atmospheric pressure with plenty of oxygen, the plants need small amounts of oxygen, and the two living things exchange gases for survival.

Some researches indicated that there were some traces of methane gas in the atmosphere, and thus it is impossible for the planet to support life (“Life of Mars,” 2013, p. 2). Nitrogen is another very important element of life, but the nitrogen levels in the atmosphere are considerably lower on the Red Planet.

Moreover, no biological process supports nitrogen fixation into the atmosphere. Thus the planet cannot support life. However, scientists believe that initially, the planet had a thick atmosphere, and people can do something to make the place habitable.

Indeed, scientists are seriously considering the idea of transforming Mars into a habitable planet. The first thing that came up was heating the polar caps to release the carbon dioxide into the atmosphere. The approach would help in thickening and warming the atmosphere, which would support liquid water that is essential for life. The considerably low temperatures would increase to manageable levels that can support life.

Scientist thought of mirrors that would reflect extra light onto the poles and warm it up. They also thought of the black color that absorbs heat, and they had the idea of sprinkling dark dust onto the poles of the Red Planet.

The most promising idea was introducing greenhouse gases into the atmosphere to warm up the planet (Marinova, 2008, para. 7). Indeed, the latter idea would be the most viable provided the scientists used greenhouse gases with long atmospheric lifetimes. This would ensure that the entire exercise would have minimal effects on the ozone layer of the planet.

Later on, researchers found out that the best greenhouse gas that can warm up the planet is perfluoropropane. This hybrid gas is a combination of all gases released by industries in the entire globe, and the gas is not portable. Therefore, the idea of introducing greenhouse gases into the red planet’s atmosphere would hold if industries were set up on Mars.

The issue was politicized, and the opposing group could not find it worthwhile to introduce the greenhouse gases that have already proved to have negative effects on the climate on Earth.

On the other hand, the scientists, who were for the idea indicated that planet Earth has an evolved ecosystem, explored the existence of various life forms; however, there is no ecosystem in Mars. Although there may be some organisms living underground, they cannot prevent explorers and scientists from undertaking their experiments.

Although some scientists are strongly proposing that they should try to establish ways through which Mars can support life, others are arguing that it is unreasonable to tamper with natural creation. Some people feel that Mars is a beautiful planet that ought to be preserved for future generations.

This is because if scientists manage to heat Mars, they may find it difficult to introduce oxygen into the atmosphere of the planet. People will have to wear oxygen masks and struggle to survive in the high-pressure atmosphere. Indeed, Earth is unique because of its ability to support life, and therefore, trying to transform Mars may sound to be theoretically feasible, but it is practically impossible.

From the discussions, it is evident that scientists are desperately looking for ways to enable Mars to support life. They are curious about finding any evidence about the ancient existence of life on the Red Planet. The scientists are not ready to quit, and they are keeping on with the search for complex organics that support life.

Although some scientists said that they had found a habitable environment on Mars, they have not shed enough light of the habitable environment on the Red Planet. Currently, there is no life on Mars, as the planet is much drier and colder than it was in the ancient days.

The scientists are continuing with their research of the ways of transforming Mars into a habitable place. It is about 50 years since the first aircraft was able to reach Mars and scientists have not yet found a viable solution. The research is ongoing, and it may take quite some time before the scientists find a way of establishing life on Mars.

Hunter, M. G. (2013). Life on Mars 3: More study of NASA’s Mars photos. Bloomington, IN: Xlibris Corporation.

Life on Mars fades after curiosity rover methane findings. (2013). The Australian , 35 (9), 1-2.

Marinova, M. (2008). Life on Mars: Terraforming the Red Planet . Web.

Space Place: Is there life on Mars? (2014). Web.

Turner, M. J. (2004). Expedition Mars . New York, NY: Springer.

• Chicago (A-D)
• Chicago (N-B)

IvyPanda. (2022, December 2). Astronomy Issues: Life on Mars. https://ivypanda.com/essays/astronomy-issues-life-on-mars/

"Astronomy Issues: Life on Mars." IvyPanda , 2 Dec. 2022, ivypanda.com/essays/astronomy-issues-life-on-mars/.

IvyPanda . (2022) 'Astronomy Issues: Life on Mars'. 2 December.

IvyPanda . 2022. "Astronomy Issues: Life on Mars." December 2, 2022. https://ivypanda.com/essays/astronomy-issues-life-on-mars/.

1. IvyPanda . "Astronomy Issues: Life on Mars." December 2, 2022. https://ivypanda.com/essays/astronomy-issues-life-on-mars/.

Bibliography

IvyPanda . "Astronomy Issues: Life on Mars." December 2, 2022. https://ivypanda.com/essays/astronomy-issues-life-on-mars/.

• Mars: The Exploration of the Red Planet
• Prospects of finding life in Mars
• A Trip to Mars: Mass Facts
• Missions to Mars: Past, Present, and Future
• Soviet Spacecraft and the Image of Venus Surface
• Astronomy Exploration of Planets and Satellites in Comparison With the Earth
• Red Giant Star - Astronomy
• Mars: Water and the Martian Landscape
• Astronomy of the Planets: Kepler's Law, Lunar Eclipse, Moon
• Mars Reconnaissance Orbiter
• The Usefulness of Earth Observation Satellites
• NASA's Lunar Surveyor Program
• Cost for Failed Systems: NASA Program
• Life outside planet Earth
• Life in This Universe

NASA Mars samples, which could contain evidence of life, will not return to Earth as initially planned

NASA's plan to retrieve as many as 30 geological samples from Mars is getting a major rewrite, agency officials said on Monday. The initial plan, which would not return the samples to Earth until 2040, was deemed "too expensive" and "unacceptably too long."

NASA is looking for a new way to get its precious Mars samples back to Earth.

Those samples are being collected by the Perseverance rover in  Mars ' Jezero Crater, which hosted a lake and a river delta billions of years ago. Getting ahold of the samples is one of NASA's top science goals; studying pristine Red Planet material in well-equipped labs around the world could reveal key insights about Mars — including, perhaps, whether it has ever hosted life, NASA officials say.

The agency has had a Mars sample-return (MSR) architecture in place for some time now, but repeated delays and cost overruns have rendered the original plan impractical, NASA officials announced on Monday (April 15).

Related: NASA's Perseverance rover may already have found signs of life on Mars, discovery of ancient lake sediments reveals

"The bottom line is that $11 billion is too expensive, and not returning samples until 2040 is unacceptably too long," NASA chief Bill Nelson said during a call with reporters.

That price tag is the upper-end estimate calculated by an independent review board, which released its findings last September. For perspective: A study from July 2020 estimated the total cost of MSR to be between $2.5 and $3 billion.

A team from within NASA analyzed those September results, determining that the agency won't be able to get Perseverance's samples back to Earth until 2040 with the established architecture. This conclusion cited reasons such as current budget constraints and the desire not to cannibalize other high-priority science efforts, like the Dragonfly drone mission to Saturn's huge moon Titan.

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

The established architecture, by the way, would have sent a NASA-built lander to Jezero Crater. This lander would have brought with it a rocket called the Mars Ascent Vehicle (MAV) and, potentially, several small retrieval helicopters akin to NASA's pioneering Ingenuity rotorcraft .

The idea was for Perseverance to drive its samples over to the lander, then load them into the MAV. The retrieval choppers may have done some of this loading work as well, especially if Perseverance wasn't in great shape by the time the lander arrived. The MAV would then have launched the samples into Mars orbit, where a spacecraft built by the  European Space Agency  would have snagged the container and hauled it back toward Earth.

NASA is now seeking a new way forward, however, in an attempt to cut costs and get the samples here sooner. Saving money will aid other agency science projects, and speeding up the timeline could help the agency plan out crewed Mars trips down the line.

"That is unacceptable, [to] wait that long," Nelson said today. "It's the decade of the 2040s that we're going to be landing astronauts on Mars ."

The wheels on the new plan (which may retain elements of the old) are already turning. NASA is asking the  Jet Propulsion Laboratory  in Southern California — its lead facility for robotic planetary exploration — and other agency research centers for innovative MSR ideas, Nelson said today.

NASA is also looking to private industry: The agency plans to release a solicitation for new ideas from the commercial sector tomorrow (April 16), Nicky Fox, associate administrator of the agency's Science Mission Directorate, said during today's call.

NASA will hold an industry day on April 22 and accept proposals through May 17, she added. The goal is to have enough information on hand by late fall or early winter to begin charting a new path forward on MSR. "We're opening this up to everyone, because we want to get every new and fresh idea that we can," Nelson said.

— Single enormous object left 2 billion craters on Mars, scientists discover

— Gargantuan volcano on Mars found hidden 'in plain sight,' and it could hold potential signs of life

— Mars-bound astronauts will face incredible stress. Here's how we can prepare them to make history.

It's unclear at this point, of course, what that new path will look like. But Fox previewed some possibilities, such as a smaller and cheaper MAV and a descoped sample-return tally (from 30 of Perseverance's sealed tubes to some unspecified lower number). Fox and Nelson both stressed that MSR remains a high priority for NASA, despite the difficulty of the task — humanity has never launched a rocket from the surface of another planet, after all (though three countries have launched from the moon) — in addition to the problems the project has experienced so far.

"I think it's fair to say that we are committed to retrieving the samples that are there — at least some of those samples," Nelson said. "We are operating from the premise that this is an important national objective."

Originally posted on Space.com .

Single enormous object left 2 billion craters on Mars, scientists discover

Gargantuan volcano on Mars found hidden 'in plain sight,' and it could hold potential signs of life

'Vampire' bacteria thirst for human blood — and cause deadly infections as they feed

Most Popular

• 2 NASA spacecraft snaps mysterious 'surfboard' orbiting the moon. What is it?
• 3 'Gambling with your life': Experts weigh in on dangers of the Wim Hof method
• 4 Viking Age women with cone-shaped skulls likely learned head-binding practice from far-flung region
• 5 'Exceptional' prosthesis of gold, silver and wool helped 18th-century man live with cleft palate
• 2 Ultrafast laser-powered 'magnetic RAM' is on the horizon after new discovery
• 3 Most massive stellar black hole in the Milky Way discovered 'extremely close' to Earth
• 4 NASA's downed Ingenuity helicopter has a 'last gift' for humanity — but we'll have to go to Mars to get it
• 5 Anglerfish entered the midnight zone 55 million years ago and thrived by becoming sexual parasites

Academia.edu no longer supports Internet Explorer.

To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to  upgrade your browser .

•  We're Hiring!
•  Help Center

Life on Mars

• Most Cited Papers
• Most Downloaded Papers
• Newest Papers
• Save to Library
• Mars Follow Following
• SETI (Search for Extraterrestrial Intelligence) Follow Following
• Grateful Dead Follow Following
• Iroquoian Societies (Archaeology) Follow Following
• Iroquoian linguistics Follow Following
• Ancient Astronaut Theory Follow Following
• Hopi studies (Anthropology) Follow Following
• Ziggurat Follow Following
• Universe expansion Follow Following
• Norse-Gaelic contact Follow Following

Enter the email address you signed up with and we'll email you a reset link.

• Academia.edu Publishing
•   We're Hiring!
•   Help Center
• Find new research papers in:
• Health Sciences
• Earth Sciences
• Cognitive Science
• Mathematics
• Computer Science
• Academia ©2024

The Australian Outback & NASA’s Search for Life on Mars

How will we know if there is life on Mars? What geological clues can our Martian orbiters and rovers search for and collect samples of to return home to Earth?

Stromatolites in the Pilbara region of Western Australia may hold the answer.

In June of 2023, members of NASA's Mars Exploration Program, the Australian Space Agency, ESA (European Space Agency), and the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO), joined together on an expedition to visit three incredible field locations containing stromatolites, fossils of ancient microbial life, and the oldest, most convincing evidence for life on Earth.

Stromatolites are rock features that are usually dome or cone-shaped, and are caused by photosynthetic lifeforms precipitating minerals throughout their life cycle, while continuously climbing upwards towards their energy source of the sun. Over time these microbial communities begin to form layers of rock that rise up to form strange shapes in the geological record that cannot be formed in any other way. Could these structures be found on other planets? On Mars?

As we search the solar system and beyond for biosignatures, or signs of life, it's crucial that we know as much as possible about the nature of life on Earth. Knowing how quickly life took hold on our planet, and how that life evolved over time, will help NASA scientists understand the possibilities for life on other worlds and how best to search for them. Mars and Earth may have had very similar pasts, and the surface of Mars shares many qualities with the stromatolite outcrops in Western Australia.

If life could take a foothold on Earth 3.5 billion years ago, could it also have taken a hold on Mars?

Learn more about the NASA Astrobiology Program: https://astrobiology.nasa.gov/

1920 x 1080

(mp4) (458.51 MB)

NASA is asking for help to retrieve Mars samples that could be the first evidence of alien life

• NASA's Perseverance Mars rover is collecting samples that could be evidence of ancient alien life.
• But NASA's Mars Sample Return mission to bring them to Earth will now cost $11 billion and take two decades.
• NASA is scrapping that plan now and asking companies for a better idea.

NASA bit off more than it could chew when it sent the Perseverance rover to Mars to collect samples.

The $2.4 billion mission landed the rover in Jezero Crater , the site of an ancient lake. It's the ideal spot to search for the fossils of Martian microbes that may have existed when the planet was lush with lakes and rivers.

Perseverance's main mission is to collect samples of the rock and sediment along the lake bed and the crater rim, in hopes of finding a sign that life once thrived on the red planet. The rover has done a fine job — so far it's secured 24 samples — but NASA no longer knows how it's going to bring them to Earth for analysis.

NASA's original design for the retrieval mission, called Mars Sample Return, has fallen apart. The agency is asking companies to step in and propose better ideas.

"We are looking at out-of-the-box possibilities that could return the samples earlier and at a lower cost," Nicola Fox, head of NASA's Science Mission Directorate, said in a press briefing on Monday. "This is definitely a very ambitious goal. We're going to need to go after some very innovative new possibilities for design, and certainly leave no stone unturned."

NASA's old plan costs $11 billion and takes too long

NASA's original proposal for the Mars Sample Return is "mind-bendingly complicated," David Parker, director of space exploration at the European Space Agency, said in 2021.

The idea was to launch two rockets toward Mars, one carrying a lander and one carrying an orbiter.

The lander would be the largest ever sent to Mars. It would touch down near the stash of samples that Perseverance set up, deploy a rover to fetch the sample tubes, and load them onto a small rocket attached to the lander.

Then the rocket would launch the samples into Mars orbit, where it would eject them toward the orbiter, which would be the largest spacecraft NASA ever sent to Mars.

The orbiter would have to grab the samples, journey back to Earth , and drop the sample vessel on a fiery plummet to our planet's surface, where a team would retrieve them.

The mission plan relied about $4 billion in new technology and a decade of mission design and construction.

But the projected cost has ballooned to $8 to $11 billion since Perseverance touched down at Jezero Crater. Independent reviews have also concluded that instead of one decade to bring the samples to Earth, it would take two.

"The bottom line is that $11 billion is too expensive, and not returning samples until 2040 is unacceptably too long," NASA Administrator Bill Nelson said in the briefing. "It's the decade of the 2040s that we're going to be landing astronauts on Mars."

At the current price tag, Mars Sample Return would "cannibalize" other NASA missions, Nelson said. So the agency is calling all hands on deck, inside and outside of NASA, to come up with a new plan.

NASA wants companies with 'tried-and-true' technology

Fox said that NASA needs to see short proposals from companies or laboratories by May 17. Then the agency will choose a few of those competitors to further develop their ideas over a 90-day period, with complete proposals on NASA's desk by late fall or early winter.

Some of NASA's most tried-and-true contractors include Lockheed Martin, Northrop Grumman, Boeing, and SpaceX. Startups like Astrobotic and Intuitive Machines are getting their foot in the NASA door through the agency's new moon program.

"What we're hoping is that we will be able to get back to some more traditional tried-and-true architectures," Fox said. "Anything requiring huge leaps in technology usually, from experience, takes a lot of time."

As for the return trip from Mars to Earth , that will be a technological leap no matter what.

"We've never launched from another planet, and that's actually what makes Mars Sample Return such a challenging and interesting mission because it really is the first of a kind," Fox said.

If you enjoyed this story, be sure to follow Business Insider on Microsoft Start.

Help | Advanced Search

Computer Science > Computation and Language

Title: researchagent: iterative research idea generation over scientific literature with large language models.

Abstract: Scientific Research, vital for improving human life, is hindered by its inherent complexity, slow pace, and the need for specialized experts. To enhance its productivity, we propose a ResearchAgent, a large language model-powered research idea writing agent, which automatically generates problems, methods, and experiment designs while iteratively refining them based on scientific literature. Specifically, starting with a core paper as the primary focus to generate ideas, our ResearchAgent is augmented not only with relevant publications through connecting information over an academic graph but also entities retrieved from an entity-centric knowledge store based on their underlying concepts, mined and shared across numerous papers. In addition, mirroring the human approach to iteratively improving ideas with peer discussions, we leverage multiple ReviewingAgents that provide reviews and feedback iteratively. Further, they are instantiated with human preference-aligned large language models whose criteria for evaluation are derived from actual human judgments. We experimentally validate our ResearchAgent on scientific publications across multiple disciplines, showcasing its effectiveness in generating novel, clear, and valid research ideas based on human and model-based evaluation results.

Submission history

Access paper:.

• Other Formats

References & Citations

• Google Scholar
• Semantic Scholar

BibTeX formatted citation

Bibliographic and Citation Tools

Code, data and media associated with this article, recommenders and search tools.

• Institution

arXivLabs: experimental projects with community collaborators

arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website.

Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them.

Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs .

Numbers, Facts and Trends Shaping Your World

Read our research on:

Full Topic List

Regions & Countries

• Publications
• Our Methods
• Short Reads
• Tools & Resources

Read Our Research On:

What the data says about abortion in the U.S.

Pew Research Center has conducted many surveys about abortion over the years, providing a lens into Americans’ views on whether the procedure should be legal, among a host of other questions.

In a  Center survey  conducted nearly a year after the Supreme Court’s June 2022 decision that  ended the constitutional right to abortion , 62% of U.S. adults said the practice should be legal in all or most cases, while 36% said it should be illegal in all or most cases. Another survey conducted a few months before the decision showed that relatively few Americans take an absolutist view on the issue .

Find answers to common questions about abortion in America, based on data from the Centers for Disease Control and Prevention (CDC) and the Guttmacher Institute, which have tracked these patterns for several decades:

How many abortions are there in the U.S. each year?

How has the number of abortions in the u.s. changed over time, what is the abortion rate among women in the u.s. how has it changed over time, what are the most common types of abortion, how many abortion providers are there in the u.s., and how has that number changed, what percentage of abortions are for women who live in a different state from the abortion provider, what are the demographics of women who have had abortions, when during pregnancy do most abortions occur, how often are there medical complications from abortion.

This compilation of data on abortion in the United States draws mainly from two sources: the Centers for Disease Control and Prevention (CDC) and the Guttmacher Institute, both of which have regularly compiled national abortion data for approximately half a century, and which collect their data in different ways.

The CDC data that is highlighted in this post comes from the agency’s “abortion surveillance” reports, which have been published annually since 1974 (and which have included data from 1969). Its figures from 1973 through 1996 include data from all 50 states, the District of Columbia and New York City – 52 “reporting areas” in all. Since 1997, the CDC’s totals have lacked data from some states (most notably California) for the years that those states did not report data to the agency. The four reporting areas that did not submit data to the CDC in 2021 – California, Maryland, New Hampshire and New Jersey – accounted for approximately 25% of all legal induced abortions in the U.S. in 2020, according to Guttmacher’s data. Most states, though,  do  have data in the reports, and the figures for the vast majority of them came from each state’s central health agency, while for some states, the figures came from hospitals and other medical facilities.

Discussion of CDC abortion data involving women’s state of residence, marital status, race, ethnicity, age, abortion history and the number of previous live births excludes the low share of abortions where that information was not supplied. Read the methodology for the CDC’s latest abortion surveillance report , which includes data from 2021, for more details. Previous reports can be found at  stacks.cdc.gov  by entering “abortion surveillance” into the search box.

For the numbers of deaths caused by induced abortions in 1963 and 1965, this analysis looks at reports by the then-U.S. Department of Health, Education and Welfare, a precursor to the Department of Health and Human Services. In computing those figures, we excluded abortions listed in the report under the categories “spontaneous or unspecified” or as “other.” (“Spontaneous abortion” is another way of referring to miscarriages.)

Guttmacher data in this post comes from national surveys of abortion providers that Guttmacher has conducted 19 times since 1973. Guttmacher compiles its figures after contacting every known provider of abortions – clinics, hospitals and physicians’ offices – in the country. It uses questionnaires and health department data, and it provides estimates for abortion providers that don’t respond to its inquiries. (In 2020, the last year for which it has released data on the number of abortions in the U.S., it used estimates for 12% of abortions.) For most of the 2000s, Guttmacher has conducted these national surveys every three years, each time getting abortion data for the prior two years. For each interim year, Guttmacher has calculated estimates based on trends from its own figures and from other data.

The latest full summary of Guttmacher data came in the institute’s report titled “Abortion Incidence and Service Availability in the United States, 2020.” It includes figures for 2020 and 2019 and estimates for 2018. The report includes a methods section.

In addition, this post uses data from StatPearls, an online health care resource, on complications from abortion.

An exact answer is hard to come by. The CDC and the Guttmacher Institute have each tried to measure this for around half a century, but they use different methods and publish different figures.

The last year for which the CDC reported a yearly national total for abortions is 2021. It found there were 625,978 abortions in the District of Columbia and the 46 states with available data that year, up from 597,355 in those states and D.C. in 2020. The corresponding figure for 2019 was 607,720.

The last year for which Guttmacher reported a yearly national total was 2020. It said there were 930,160 abortions that year in all 50 states and the District of Columbia, compared with 916,460 in 2019.

• How the CDC gets its data: It compiles figures that are voluntarily reported by states’ central health agencies, including separate figures for New York City and the District of Columbia. Its latest totals do not include figures from California, Maryland, New Hampshire or New Jersey, which did not report data to the CDC. ( Read the methodology from the latest CDC report .)
• How Guttmacher gets its data: It compiles its figures after contacting every known abortion provider – clinics, hospitals and physicians’ offices – in the country. It uses questionnaires and health department data, then provides estimates for abortion providers that don’t respond. Guttmacher’s figures are higher than the CDC’s in part because they include data (and in some instances, estimates) from all 50 states. ( Read the institute’s latest full report and methodology .)

While the Guttmacher Institute supports abortion rights, its empirical data on abortions in the U.S. has been widely cited by  groups  and  publications  across the political spectrum, including by a  number of those  that  disagree with its positions .

These estimates from Guttmacher and the CDC are results of multiyear efforts to collect data on abortion across the U.S. Last year, Guttmacher also began publishing less precise estimates every few months , based on a much smaller sample of providers.

The figures reported by these organizations include only legal induced abortions conducted by clinics, hospitals or physicians’ offices, or those that make use of abortion pills dispensed from certified facilities such as clinics or physicians’ offices. They do not account for the use of abortion pills that were obtained  outside of clinical settings .

(Back to top)

The annual number of U.S. abortions rose for years after Roe v. Wade legalized the procedure in 1973, reaching its highest levels around the late 1980s and early 1990s, according to both the CDC and Guttmacher. Since then, abortions have generally decreased at what a CDC analysis called  “a slow yet steady pace.”

Guttmacher says the number of abortions occurring in the U.S. in 2020 was 40% lower than it was in 1991. According to the CDC, the number was 36% lower in 2021 than in 1991, looking just at the District of Columbia and the 46 states that reported both of those years.

(The corresponding line graph shows the long-term trend in the number of legal abortions reported by both organizations. To allow for consistent comparisons over time, the CDC figures in the chart have been adjusted to ensure that the same states are counted from one year to the next. Using that approach, the CDC figure for 2021 is 622,108 legal abortions.)

There have been occasional breaks in this long-term pattern of decline – during the middle of the first decade of the 2000s, and then again in the late 2010s. The CDC reported modest 1% and 2% increases in abortions in 2018 and 2019, and then, after a 2% decrease in 2020, a 5% increase in 2021. Guttmacher reported an 8% increase over the three-year period from 2017 to 2020.

As noted above, these figures do not include abortions that use pills obtained outside of clinical settings.

Guttmacher says that in 2020 there were 14.4 abortions in the U.S. per 1,000 women ages 15 to 44. Its data shows that the rate of abortions among women has generally been declining in the U.S. since 1981, when it reported there were 29.3 abortions per 1,000 women in that age range.

The CDC says that in 2021, there were 11.6 abortions in the U.S. per 1,000 women ages 15 to 44. (That figure excludes data from California, the District of Columbia, Maryland, New Hampshire and New Jersey.) Like Guttmacher’s data, the CDC’s figures also suggest a general decline in the abortion rate over time. In 1980, when the CDC reported on all 50 states and D.C., it said there were 25 abortions per 1,000 women ages 15 to 44.

That said, both Guttmacher and the CDC say there were slight increases in the rate of abortions during the late 2010s and early 2020s. Guttmacher says the abortion rate per 1,000 women ages 15 to 44 rose from 13.5 in 2017 to 14.4 in 2020. The CDC says it rose from 11.2 per 1,000 in 2017 to 11.4 in 2019, before falling back to 11.1 in 2020 and then rising again to 11.6 in 2021. (The CDC’s figures for those years exclude data from California, D.C., Maryland, New Hampshire and New Jersey.)

The CDC broadly divides abortions into two categories: surgical abortions and medication abortions, which involve pills. Since the Food and Drug Administration first approved abortion pills in 2000, their use has increased over time as a share of abortions nationally, according to both the CDC and Guttmacher.

The majority of abortions in the U.S. now involve pills, according to both the CDC and Guttmacher. The CDC says 56% of U.S. abortions in 2021 involved pills, up from 53% in 2020 and 44% in 2019. Its figures for 2021 include the District of Columbia and 44 states that provided this data; its figures for 2020 include D.C. and 44 states (though not all of the same states as in 2021), and its figures for 2019 include D.C. and 45 states.

Guttmacher, which measures this every three years, says 53% of U.S. abortions involved pills in 2020, up from 39% in 2017.

Two pills commonly used together for medication abortions are mifepristone, which, taken first, blocks hormones that support a pregnancy, and misoprostol, which then causes the uterus to empty. According to the FDA, medication abortions are safe  until 10 weeks into pregnancy.

Surgical abortions conducted  during the first trimester  of pregnancy typically use a suction process, while the relatively few surgical abortions that occur  during the second trimester  of a pregnancy typically use a process called dilation and evacuation, according to the UCLA School of Medicine.

In 2020, there were 1,603 facilities in the U.S. that provided abortions,  according to Guttmacher . This included 807 clinics, 530 hospitals and 266 physicians’ offices.

While clinics make up half of the facilities that provide abortions, they are the sites where the vast majority (96%) of abortions are administered, either through procedures or the distribution of pills, according to Guttmacher’s 2020 data. (This includes 54% of abortions that are administered at specialized abortion clinics and 43% at nonspecialized clinics.) Hospitals made up 33% of the facilities that provided abortions in 2020 but accounted for only 3% of abortions that year, while just 1% of abortions were conducted by physicians’ offices.

Looking just at clinics – that is, the total number of specialized abortion clinics and nonspecialized clinics in the U.S. – Guttmacher found the total virtually unchanged between 2017 (808 clinics) and 2020 (807 clinics). However, there were regional differences. In the Midwest, the number of clinics that provide abortions increased by 11% during those years, and in the West by 6%. The number of clinics  decreased  during those years by 9% in the Northeast and 3% in the South.

The total number of abortion providers has declined dramatically since the 1980s. In 1982, according to Guttmacher, there were 2,908 facilities providing abortions in the U.S., including 789 clinics, 1,405 hospitals and 714 physicians’ offices.

The CDC does not track the number of abortion providers.

In the District of Columbia and the 46 states that provided abortion and residency information to the CDC in 2021, 10.9% of all abortions were performed on women known to live outside the state where the abortion occurred – slightly higher than the percentage in 2020 (9.7%). That year, D.C. and 46 states (though not the same ones as in 2021) reported abortion and residency data. (The total number of abortions used in these calculations included figures for women with both known and unknown residential status.)

The share of reported abortions performed on women outside their state of residence was much higher before the 1973 Roe decision that stopped states from banning abortion. In 1972, 41% of all abortions in D.C. and the 20 states that provided this information to the CDC that year were performed on women outside their state of residence. In 1973, the corresponding figure was 21% in the District of Columbia and the 41 states that provided this information, and in 1974 it was 11% in D.C. and the 43 states that provided data.

In the District of Columbia and the 46 states that reported age data to  the CDC in 2021, the majority of women who had abortions (57%) were in their 20s, while about three-in-ten (31%) were in their 30s. Teens ages 13 to 19 accounted for 8% of those who had abortions, while women ages 40 to 44 accounted for about 4%.

The vast majority of women who had abortions in 2021 were unmarried (87%), while married women accounted for 13%, according to  the CDC , which had data on this from 37 states.

In the District of Columbia, New York City (but not the rest of New York) and the 31 states that reported racial and ethnic data on abortion to  the CDC , 42% of all women who had abortions in 2021 were non-Hispanic Black, while 30% were non-Hispanic White, 22% were Hispanic and 6% were of other races.

Looking at abortion rates among those ages 15 to 44, there were 28.6 abortions per 1,000 non-Hispanic Black women in 2021; 12.3 abortions per 1,000 Hispanic women; 6.4 abortions per 1,000 non-Hispanic White women; and 9.2 abortions per 1,000 women of other races, the  CDC reported  from those same 31 states, D.C. and New York City.

For 57% of U.S. women who had induced abortions in 2021, it was the first time they had ever had one,  according to the CDC.  For nearly a quarter (24%), it was their second abortion. For 11% of women who had an abortion that year, it was their third, and for 8% it was their fourth or more. These CDC figures include data from 41 states and New York City, but not the rest of New York.

Nearly four-in-ten women who had abortions in 2021 (39%) had no previous live births at the time they had an abortion,  according to the CDC . Almost a quarter (24%) of women who had abortions in 2021 had one previous live birth, 20% had two previous live births, 10% had three, and 7% had four or more previous live births. These CDC figures include data from 41 states and New York City, but not the rest of New York.

The vast majority of abortions occur during the first trimester of a pregnancy. In 2021, 93% of abortions occurred during the first trimester – that is, at or before 13 weeks of gestation,  according to the CDC . An additional 6% occurred between 14 and 20 weeks of pregnancy, and about 1% were performed at 21 weeks or more of gestation. These CDC figures include data from 40 states and New York City, but not the rest of New York.

About 2% of all abortions in the U.S. involve some type of complication for the woman , according to an article in StatPearls, an online health care resource. “Most complications are considered minor such as pain, bleeding, infection and post-anesthesia complications,” according to the article.

The CDC calculates  case-fatality rates for women from induced abortions – that is, how many women die from abortion-related complications, for every 100,000 legal abortions that occur in the U.S .  The rate was lowest during the most recent period examined by the agency (2013 to 2020), when there were 0.45 deaths to women per 100,000 legal induced abortions. The case-fatality rate reported by the CDC was highest during the first period examined by the agency (1973 to 1977), when it was 2.09 deaths to women per 100,000 legal induced abortions. During the five-year periods in between, the figure ranged from 0.52 (from 1993 to 1997) to 0.78 (from 1978 to 1982).

The CDC calculates death rates by five-year and seven-year periods because of year-to-year fluctuation in the numbers and due to the relatively low number of women who die from legal induced abortions.

In 2020, the last year for which the CDC has information , six women in the U.S. died due to complications from induced abortions. Four women died in this way in 2019, two in 2018, and three in 2017. (These deaths all followed legal abortions.) Since 1990, the annual number of deaths among women due to legal induced abortion has ranged from two to 12.

The annual number of reported deaths from induced abortions (legal and illegal) tended to be higher in the 1980s, when it ranged from nine to 16, and from 1972 to 1979, when it ranged from 13 to 63. One driver of the decline was the drop in deaths from illegal abortions. There were 39 deaths from illegal abortions in 1972, the last full year before Roe v. Wade. The total fell to 19 in 1973 and to single digits or zero every year after that. (The number of deaths from legal abortions has also declined since then, though with some slight variation over time.)

The number of deaths from induced abortions was considerably higher in the 1960s than afterward. For instance, there were 119 deaths from induced abortions in  1963  and 99 in  1965 , according to reports by the then-U.S. Department of Health, Education and Welfare, a precursor to the Department of Health and Human Services. The CDC is a division of Health and Human Services.

Note: This is an update of a post originally published May 27, 2022, and first updated June 24, 2022.

Support for legal abortion is widespread in many countries, especially in Europe

Nearly a year after roe’s demise, americans’ views of abortion access increasingly vary by where they live, by more than two-to-one, americans say medication abortion should be legal in their state, most latinos say democrats care about them and work hard for their vote, far fewer say so of gop, positive views of supreme court decline sharply following abortion ruling, most popular.

1615 L St. NW, Suite 800 Washington, DC 20036 USA (+1) 202-419-4300 | Main (+1) 202-857-8562 | Fax (+1) 202-419-4372 |  Media Inquiries

Research Topics

• Age & Generations
• Coronavirus (COVID-19)
• Economy & Work
• Family & Relationships
• Gender & LGBTQ
• Immigration & Migration
• International Affairs
• Internet & Technology
• Methodological Research
• News Habits & Media
• Non-U.S. Governments
• Other Topics
• Politics & Policy
• Race & Ethnicity
• Email Newsletters

ABOUT PEW RESEARCH CENTER  Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping the world. It conducts public opinion polling, demographic research, media content analysis and other empirical social science research. Pew Research Center does not take policy positions. It is a subsidiary of  The Pew Charitable Trusts .

Copyright 2024 Pew Research Center

Terms & Conditions

Privacy Policy

Cookie Settings

Reprints, Permissions & Use Policy