After analyzing powdered rock samples collected from the surface of Mars by NASA’s Curiosity rover, scientists today announced that several of the samples are rich in a type of carbon that on Earth is associated with biological processes.
While the finding is intriguing, it doesn’t necessarily point to ancient life on Mars, as scientists have not yet found conclusive supporting evidence of ancient or current biology there, such as sedimentary rock formations produced by ancient bacteria, or a diversity of complex organic molecules formed by life.
“We’re finding things on Mars that are tantalizingly interesting, but we would really need more evidence to say we’ve identified life,” said Paul Mahaffy, who served as the principal investigator of the Sample Analysis at Mars (SAM) chemistry lab aboard Curiosity until retiring from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in December 2021. “So we’re looking at what else could have caused the carbon signature we’re seeing, if not life.”
This image shows the Highfield drill hole made by NASA’s Curiosity rover as it was collecting a sample on Vera Rubin Ridge in Gale crater on Mars. Drill powder from this hole was enriched in carbon 12. The image was taken by the Mars Hand Lens Imager on the 2,247th Martian day, or sol, of the mission.Credits: NASA/Caltech-JPL/MSSS.
In a report of their findings to be published in the Proceedings of the National Academy of Sciences journal on January 18, Curiosity scientists offer several explanations for the unusual carbon signals they detected. Their hypotheses are drawn partly from carbon signatures on Earth, but scientists warn the two planets are so different they can’t make definitive conclusions based on Earth examples.
“The hardest thing is letting go of Earth and letting go of that bias that we have and really trying to get into the fundamentals of the chemistry, physics and environmental processes on Mars,” said Goddard astrobiologist Jennifer L. Eigenbrode, who participated in the carbon study. Previously, Eigenbrode led an international team of Curiosity scientists in the detection of myriad organic molecules — ones that contain carbon — on the Martian surface.
“We need to open our minds and think outside the box,” Eigenbrode said, “and that’s what this paper does.”
The biological explanation Curiosity scientists present in their paper is inspired by Earth life. It involves ancient bacteria in the surface that would have produced a unique carbon signature as they released methane into the atmosphere where ultraviolet light would have converted that gas into larger, more complex molecules. These new molecules would have rained down to the surface and now could be preserved with their distinct carbon signature in Martian rocks.
Two other hypotheses offer nonbiological explanations. One suggests the carbon signature could have resulted from the interaction of ultraviolet light with carbon dioxide gas in the Martian atmosphere, producing new carbon-containing molecules that would have settled to the surface. And the other speculates that the carbon could have been left behind from a rare event hundreds of millions of years ago when the solar system passed through a giant molecular cloud rich in the type of carbon detected.
“All three explanations fit the data,” said Christopher House, a Curiosity scientist based at Penn State who led the carbon study. “We simply need more data to rule them in or out.”
Learn More:
With Mars Methane Mystery Unsolved, Curiosity Serves Scientists a New One: Oxygen
First You See It, Then You Don’t: Scientists Closer to Explaining Mars Methane Mystery
NASA’s Curiosity Rover Finds Clues to Chilly Ancient Mars Buried in Rocks
To analyze carbon in the Martian surface, House’s team used the Tunable Laser Spectrometer (TLS) instrument inside the SAM lab. SAM heated 24 samples from geologically diverse locations in the planet’s Gale crater to about 1,500 degrees Fahrenheit, or 850 degrees Celsius, to release the gases inside. Then the TLS measured the isotopes from some of the reduced carbon that was set free in the heating process. Isotopes are atoms of an element with different masses due to their distinct number of neutrons, and they are instrumental in understanding the chemical and biological evolution of planets.
Carbon is particularly important since this element is found in all life on Earth; it flows continuously through the air, water, and ground in a cycle that’s well understood thanks to isotope measurements.
For instance, living creatures on Earth use the smaller, lighter carbon 12 atom to metabolize food or for photosynthesis versus the heavier carbon 13 atom. Thus, significantly more carbon 12 than carbon 13 in ancient rocks, along with other evidence, suggests to scientists they’re looking at signatures of life-related chemistry. Looking at the ratio of these two carbon isotopes helps Earth scientists tell what type of life they’re looking at and the environment it lived in.
On Mars, Curiosity researchers found that nearly half of their samples had surprisingly large amounts of carbon 12 compared to what scientists have measured in the Martian atmosphere and meteorites. These samples came from five distinct locations in Gale crater, the researchers report, which may be related in that all the locations have well-preserved, ancient surfaces.
“On Earth, processes that would produce the carbon signal we’re detecting on Mars are biological,” House said. “We have to understand whether the same explanation works for Mars, or if there are other explanations, because Mars is very different.”
Mars is unique because it may have started off with a different mix of carbon isotopes than Earth 4.5 billion years ago. Mars is smaller, cooler, has weaker gravity, and different gases in its atmosphere. Additionally, the carbon on Mars could be cycling without any life involved.
“There’s a huge chunk of the carbon cycle on Earth that involves life, and because of life, there is a chunk of the carbon cycle on Earth we can’t understand, because everywhere we look there is life,” said Andrew Steele, a Curiosity scientist based at the Carnegie Institution for Science in Washington, D.C.
This mosaic was made from images taken by the Mast Camera aboard NASA’s Curiosity rover on the 2,729th Martian day, or sol, of the mission. It shows the landscape of the Stimson sandstone formation in Gale crater. In this general location, Curiosity drilled the Edinburgh drill hole, a sample from which was enriched in carbon 12.Credits: NASA/Caltech-JPL/MSSS
Steele noted that scientists are in the early stages of understanding how carbon cycles on Mars and, thus, how to interpret isotopic ratios and the nonbiological activities that could lead to those ratios. Curiosity, which arrived on the Red Planet in 2012, is the first rover with tools to study carbon isotopes in the surface. Other missions have collected information about isotopic signatures in the atmosphere, and scientists have measured ratios of Martian meteorites that have been collected on Earth.
“Defining the carbon cycle on Mars is absolutely key to trying to understand how life could fit into that cycle,” Steele said. “We have done that really successfully on Earth, but we are just beginning to define that cycle for Mars.”
Curiosity scientists will continue to measure carbon isotopes to see if they get a similar signature when the rover visits other sites suspected to have well-preserved ancient surfaces. To further test the biological hypothesis involving methane-producing microorganisms, the Curiosity team would like to analyze the carbon content of a methane plume released from the surface. The rover unexpectedly encountered such a plume in 2019 but there’s no way to predict whether that will happen again. Otherwise, researchers point out that this study provides guidance to the team behind NASA’s Perseverance rover on the best types of samples to collect to confirm the carbon signature and determine definitively whether it’s coming from life or not. Perseverance is collecting samples from the Martian surface for possible future return to Earth.
Curiosity’s mission is led by NASA’s Jet Propulsion Laboratory in Southern California; JPL is managed by Caltech.Banner image: NASA’s Curiosity rover captured these clouds just after sunset on March 19, 2021, the 3,063rd Martian day, or sol, of the rover’s mission. The image is made up of 21 individual images stitched together and color-corrected so that the scene appears as it would to the human eye. Credits: NASA/JPL-Caltech/MSSS
By Lonnie Shekhtman
NASA’s Goddard Space Flight Center, Greenbelt, Md.Last Updated: Jan 18, 2022Editor: Svetlana Shekhtman
Interesting. The image of the sample site looks like supergene carbonate filling cracks, most likely calcite, so I quickly read several articles about carbon isotope fractionation during supergene processes. It appears that C13 is less mobile than C12, and C12 is enriched in supergene carbonates. If the white material filling the cracks in the rock are not carbonates…never mind. Sooner or later the question of “life” on Mars will be answered, if pond scum constitutes life.
The C12 cloud hypothesis is relatively easy to test. If the Carbon rained down from the Solar System passing through a cloud, then the same C12 signature would exist on the Moon at the same geologic time.
I agree that the fracture fillings look like calcite or dolomite, but not sure about a supergene origin. They are clearly brittle fractures and the host rock is said to be sandstone, so they are probably post-lithification fractures. I would guess they are a late-diagenetic feature.
Sandstones don’t typically have a lot of carbonate, so I wonder if the presence of what obviously looks like carbonate, was why they chose that site for their carbon isotope study. They have a whole array of analytical instruments, and could probably tell us what the mineralogy is.
I’m always amazed at how familiar those Martian rocks look. The photos could have been taken in any desert or Arctic island, here on Earth.
Yep… Apart from having much lower quartz content, Martian sedimentary rocks and sequences are stunningly Earth-like.
Regarding Martian carbonates, this is a good article:
https://eos.org/research-spotlights/detecting-carbonates-on-the-surface-of-mars
If not for the climate change scam, I’d be tempted to join the AGU, just for the planetary geology papers.
Yeah I use to be an AGI member but they have lost the ball with regards to anything climate. I agree it’s a good article.
It’s getting harder and harder to renew my AAPG and SEG memberships.
I almost did drop SEG. But, I’ve been a member of SEG for just over 40 years… I figured I’d stay in.
Still have my AAPG. So fa they don’t seem to be too “woke”, so to speak 🙂
They’re working on it… https://explorer.aapg.org/story/articleid/62206/beyond-oil-and-gas-alliance-launches-at-cop26
Oh well….AAPG gotta jump on that bandwagon I guess. So sad.
David, I dropped my SEG membership when they referred to Exploration Geologists as “Technicians”.
Or on Devon Island.
salts
anyone who likes imagery from Mars be sure to check out the following YouTube site all in 4K
https://www.youtube.com/c/framesbyrado/videos
About 15 years ago I had a large printer and took one of the 360° views of the Martian landscape and printed it out at 2.5′ X 18′, 300dpi. Made a great scene for my grandson’s room.
This is interesting, not to all of us tho, as it points directly at my long & oft asserted assertion that “The human animal cannot lie”
Quote:”While blah blah doesn’t necessarily point to ancient life on Mars, blah blah blah such as sedimentary rock formations produced by ancient *bacteria*, or a blah blah formed by life.
(blahs added in an attempt to reduce wind and aid clarity)
See that, do you actually see that?
They say that bacteria are an essential for there to be Life On Anywhere, even if the bacteria are The Only Life
Thus and therefore, The Enquiring Mind tap tap tapping on this keyboard here & now *DEMANDS* to know:
Why humanity right now (and for the last 10,000+ yrs) is and has been hell-bent on destroying The Most Massive and Important reservoir of bacterial life on this Earth?
i.e. The soil, the dirt, the A Horizon or whatever you call it wherever your keyboard is.
In view of what the all the powerful bend-over and be s**gg*d senseless fawn, grovel, pray & obey, give them money NASA says:
What will happen when we complete our work of destroying all those bacteria – and filling the sky with CO2 as a consequence, a’la Mars?
We truly are in A Dark Age
It is nice that ‘squirrels’ can be relied upon to lighten the gloom, doncha think?
“my long & oft asserted assertion that “The human animal cannot lie”
And yet politicians, media, sections of academia and even Nobel victim winners such as Michael Mann often do.
Therefore, they must not be human?
“my long & oft asserted assertion that “The human animal cannot lie”
Is brimming with wrongability
Actually, we aren’t destroying the soil.
I don’t share your circuitous pessimism. Bacteria aren’t necessarily essential to other forms of life. They are merely very simple forms that usually precede more complex forms. In that the more complex forms can benefit from the bacteria in symbiosis or other relationships is often common, however not essential.
To hyperbolically say that NASA’s goal is to destroy Martian bacteria is utterly non-sequitur.
Just dangling the possibility of life out there to get more funding. Let’s face it, the American public isn’t going to want to keep sending Mars rovers if it’s a dead planet and always has been.
I agree. So little science, so much science fiction. Anyone with half a brain knows there was never is not now, never will be life on Mars.👽
TG – Based on good science investigations over the past half of a century, has shown that Mars likely had significant liquid water present around 3- to 3.5-billion years ago and may still have large amount of water (as ice) just under the ground surface. As best we know, water is a key ingredient for life (among others) and given that Mars “cooled” or “evolved” earlier than the Earth there is the possibility that life (bacteria, virus, etc) evolved on Mars early in it’s history. So far the search results have been ambiguous but with tantalizing hints that life likely did exist on Mars sometime in the past. Keep in mind that although we have gained tremendous science knowledge about Mars through rovers and other observatories, we still have barely scratched the proverbial surface of the planet. Perhaps we have just not look in the right spot.
We know of no other life (dead or alive) in our solar system. The finding that Mars actually did have ancient life would be one of the greatest discoveries ever made. No “science fiction” here.
Water is one of the most abundant substances in the universe, and no guarantee of life.
Liquid water does not appear to be abundant in the universe. Although some of the Jovian and Saturnian moons may have liquid water under their ice crusts.
On Earth, some form of life appears to be present wherever persistent liquid water is present. There’s only one example on Earth where there is abundant liquid water and no life at all.
https://www.universetoday.com/144161/finally-scientists-find-a-place-on-earth-with-liquid-water-but-no-life/
While, evidence of past liquid water on Mars is no guarantee that life evolved there at some point in the past, it’s the best place to look for it. If present, evidence of past Martian life (fossils) will be found in its sedimentary rocks, particularly the shale (mudstone) formations. Curiosity has already documented many geological features in Gale Crater that are morphologically similar to fossilized stromatolites, lichens, algae, algal mats, etc.
https://wattsupwiththat.com/2020/04/15/stromatolites-on-mars/
However, until samples of those rocks can be brought back to Earth and physically examined, we won’t know if those examples are fossils or the result of abiotic processes. Even then, we might not know for sure… Science is never settled.
Dave, take a look at this article: https://www.goodnewsnetwork.org/mysterious-purple-coating-found-on-mars-rocks-in-every-direction/
I saw that headline, but haven’t had time to read it yet.
Thomas,
Nobody “knows” anything of the sort. You are, of course, entitled to your opinion, but to present it as knowledge is disingenuous at the very least.
Notice there are 4 downvotes on a basic fact. By Apollo 13, no one cared anymore. Yet the next rover digging through rocks is supposed to gain interest?
We don’t really have to worry about the American public losing interest in exploring Mars. And I’m not agreeing that is the case. But there are enough billionaires interested in the subject, to make it happen, whether the public is enthusiastic about it or not.
What an absurd prediction.
How exactly is the existence of “life as we know it” a prerequisite for exploration and colonization? Life as we know it certainly doesn’t exist in space, but there we are. It certainly doesn’t exist on the moon, but we will within our lifetimes.
Such utterings are made by fearful homebodies. Let them inherit the earth. I’m going for the stars.
The public doesn’t care what you consider to be reasons to explore. I’m all for pure research. But the NASA PR machine is sickening.
Now that NASA knows that rock samples could be riddled with Carbon I guess they’ll be leaving them in the ground… </sarc>
“All three explanations fit the data,”
I found this phrase especially refreshing, while wondering how it got past the propaganda department editors.
They must be geologists! 😉
David, as a geologist, did you note the passage, “geologically diverse locations in the planet’s Gale crater“?
What created the Gale Crater? Volcanoes or meteors come to mind for craters on earth.
If Gale was a ‘Ice Comet’ creation, would / could that change the Carbon signal that they found?
Gale Crater and Jezero Crater are impact craters. Probably from large metallic or chondritic asteroid impacts about 4 billion years ago. Over the next few hundred million years, the craters were filled with fairly deep lakes. The evidence of fluvial (stream) and lacustrine (lake) erosion and deposition is extensive. By about 3-3.5 billion years ago, the lakes dried up and Mars’ sedimentary processes have largely been restricted to aeolian (wind-driven) processes.
Both craters are geologically diverse. There are basaltic igneous rocks & breccias related to impacts, conglomerate, sandstone, shale (mudstone) & carbonate rocks related to fluvial and lacustrine processes and sandstones & siltstones related to aeolian processes.
The carbon isotope anomalies probably aren’t related to the original impacts. Most likely they are related to the three processes discussed in the article. Although, we don’t even know what we don’t know about Mars. There could be other geochemical processes that haven’t been thought of yet.
“We simply need more data to rule them in or out.”
Science never positively rules in, it only can rule out through observation.
These folks might need to learn from Popper and Feynman.
The starting point in geology is Chamberlin’s Method of Multiple Working Hypotheses. Working hypotheses are different explanations that all fit the data. You work all the multiple hypotheses. Some are ruled out, some are ruled in, over time as more observations and data are collected and as methods of testing the hypotheses are refined. Some working hypotheses remain “on the bubble,” neither ruled in or out.
There rarely are “unique” solutions in geology.
Enlightening. I’ve never heard this method ascribed to a particular individual or field. To me it was always just a part of the scientific method, akin to “not leaping to conclusions”.
When you’re working on rock outcrops, it’s usually best to avoid leaping to anything… 😉
Thanks David, it’s always a good day to learn.
Unless you need some exercise 🙂
NASA is so chary of making any bold claims regarding evidence of life on Mars, but can’t wait to regale us with the latest climate catastrophe prognostication on far flimsier evidence. Go figure.
Climate science is overwhelmingly politicized; Mars science is not. That is the difference.
Since C12 constitutes 99% of all carbon on Earth, how could life NOT be composed primarily of C12?
It is. WHere did you see it’s not?
I was responding to the article that said: “scientists today announced that several of the samples are rich in a type of carbon that on Earth is associated with biological processes.”
That statement only means something if Earth life had another carbon option.
It is loosely worded. More precisely, the samples are enriched in C12. That is, the ratio C12/C13 is higher in samples associated with life than abiotic samples.
On Earth, the enrichment of C12 is miniscule because C13 is almost unavailable. Abiotic C12= 98.9%.
C4 plants are 99.21% C12, C3 plants are 99.24% C12.
That is not a difference that would indicate life is causing C12 enrichment on Mars, since the C12/C13 ratio on Mars is so different.
Just curious as I don’t know the answer, but how would the lack of a magnetic field affect the formation of carbon isotopes on Mars? Is it possible that the C12:C13:C14 ratios observed are not just the natural result of a very different radiation exposure history?
On Earth, with the exception of C14, I believe that the overwhelming bulk of carbon 12 and 13 where formed in supernovae although biological process have modified the overall percentages that we see in the biosphere.
I forgot to clarify that the “star explosion” events would decide the overall percentages of C12 and C13 in our solar system. So the ration should be very similar on Mars baring biological modification. On Earth C14 is created, in part, by cosmic ray interaction with nitrogen in the atmosphere. I’m not so sure about Mars
Are there non-biogenic caches of carbon that are higher in C13% than is found in the biosphere? I thought the Earth as a whole was 99% C12.
By digging further, I discovered a can of worms. It appears the overall ratio of C12 is quoted at 93%, but nearly everything measured has a much higher ratio of C12, including carbonatites. I could not find how that 93% C12 was derived.
Surprisingly, placer diamonds have one of the highest C12 ratios, suspected to be due to contamination…contaminated by what, or how a diamond can be contaminated once on the surface – crickets.
Although everyone agrees that plants preferentially select C12, no one suggests where the C13 is accumulating.
Not sure where the C12 abundance of 93% is from but the abundance is much closer to 99% (98.93%). Diamonds are not one of my specialties; I work with oil & natural gas source rock and forensics. I believe the “contamination” may refer to incorporation of surface carbon into the lower crust/upper mantle through plate tectonics like processes that alter the expected or “normal” diamond carbon ratios. I’ll see if I can find a good reference to post. Diamonds are their own special cases of “weird”.
The enrichment of C13 is on a very small scale. Bacteria and plants and some nonbiological processes do show C13 isotope fractalization effect due to the preferential use of C12. I would not characterize the enrichment as accumulation and I hope my earlier posts did not suggest that.
I’m not sure what you mean by “non-biological caches” but most carbon on earth is C12 (as you noted; C12 natural abundance 98.93 %, C13 abundance 1.07%). The very small percentage of C13 can be enriched by biological (mostly bacterial) processes that favor usage of C12 and resulting in enrichment of the C13 isotope (C12 to C12 chemical bonds are easier to break than C13 to C13 bonds). Admittedly this enrichment is relatively minor but is measurable and often a very good diagnostic tool when investigating oil and natural gas source rocks, biological sciences (food web evaluation), archology (ancient diets and agriculture), forensics, food industry (food adulteration), and sports regulation (performance enhancing drugs).
Seem like the quest has moved from searching for “life as we know it” to “bacteria as we know them” to “evidence of long dead biomarkers”. Sooner or later the bar will be set low enough to justify something scientific, instead of governments financing sexy stuff to show off their technical prowess.
I described this article to my wife, and her response was “can’t they just wait a couple of years and ask Musk about it when he gets there?”
Seriously, though, this really is fascinating. Thanks for posting it.
Put the idea out to the media by (correctly) denying it as a probable explanation.
Are they being half-way honest, or half-way dishonest?
From the article: ““We simply need more data to rule them in or out.””
Too bad alarmist climate scientists don’t have the same attitude.
Low temperature chemistry would also favor C-12. Detection of a large chiral excess would be strong evidence of life.