Editor’s note: This guest post was written by Andy Tomaswick, an electrical engineer who follows space science and technology.
The search for biologically created organic molecules on Mars goes back at least to the 1970s with the Viking program. Those missions had famously mixed results, and so the search for carbon-based life on Mars continues to this day. Researchers keeping piling on more and more evidence to excite astrobiologists and new results published in a study by the Planetary Science Institute and the Carnegie Institute of Washington may heighten their enthusiasm.
The latest results come from a team led by Andrew Steele of the Carnegie Institution for Science who surveyed meteorites from Mars, which covered a 4.2 billion year time span of Martian geology. While it is no surprise that there are organics on Mars — that Martian meteorites contain carbon-based molecules has been known for years — the team confirmed those findings by detecting organics on ten of the eleven meteorites they examined. However, questions remained as to where exactly the meteorite-bound organic molecules came from and, if they were from Mars, what had created them?
The team set out to answer these questions and came to the conclusion that the molecules are indeed from Mars and not the result of some cross-contamination from Earth’s biosphere. However, they also found that the molecules were not created by any biological process. The organics actually formed in the chunks of rock that later became the meteorites that transported them to earth. Their formation was part of a volcanic process that traps carbon in crystal structures formed by cooling magma. Through a series of non-biological chemical reactions, the complex organics found in the meteorites are created using the carbon trapped in these crystals.
The team also casts doubt on another possible explanation: whether the organics might be caused by emissions from microbes that had migrated into the volcano via tectonic processes similar to those on Earth. They point out that Mars does not have the tectonic activity similar to Earth so there is very little likelihood that the molecules are created by microbial activity.
That might sound like a depressing result for the astrobiologists. But the important finding from this study is that Mars has been natively and naturally creating complex organic molecules for 4.2 billion years and may be still be doing so today. Since the creation of organic molecules on Earth was a precursor to life, scientists can still hold out hope that the same life-creating process might have already happened on the red planet.
Interestingly, one of the Martian meteorites that was studied was the famous ALH84001, the meteorite that some researchers claimed in 1996 might contain fossils from Mars. That claim was subsequently strongly challenged, and studies of the rock are ongoing. ALH84001 is a portion of a meteorite that was dislodged from Mars by a huge impact about 16 million years ago and that fell to Earth in Antarctica approximately 13,000 years ago. The meteorite was found in Allan Hills ice field in Antarctica.
Lead image caption: ALH84001 is one of 10 rocks from Mars in which researchers have found organic carbon compounds that originated on Mars without involvement of life. Credit: NASA/JSC/Stanford University
Sources: Planetary Science Institute, LiveScience, NASA
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Methane caused by geological processes, organic chemicals in meteorites caused by geological processes … the case for life on Mars isn’t looking up these days! 🙁
Don’t forget that the recent signs of water including sediments can be the result of brief periods of snowmelt as Mars axis wanders chaotically. This means that there have been such surface habitable periods interspersed with massive sterile ones, and that perhaps the only large scale habitable period was before the large heavy bombardment.
On the other hand that early period seems to have been very habitable as per recent finds, and the crust should have been a nice refugia for life afterwards. In any case, extinct or extant life, we may find some.
How long was that early period of habitability? How would we find life on Mars if it is buried deep underground? Would there be fossilized evidence of simple life on the surface of Mars?
– I think the existence and length of the habitable period is debated, but up to the Late Heavy Bombardment has been mentioned in the NASA meeting on Mars exploration that was web published this week.
But as on Earth, we should likely expect extant monocellular life to survive in the crust, because in simple models it proliferates faster than any reasonable rate of impactors can sterilize. However, that result seems not much spread or even accepted as of yet.
– The two last questions I already described in a lengthy reply to Dampe above.
I disagree – I think its stock goes up almost daily!
This interesting release just came out: http://carnegiescience.edu/news/extensive_water_mar%E2%80%99s_interior
All the ingredients are there. We just have to find the cake!
…or make our own.
Good catch! I have commented elsewhere but should repeat:
The abstract (IIRC today) goes on to show how the initial water content was 10 times larger, meaning Mars and Earth-Moon terrestrials place on ~ 0.5 % of water. 5 times less water and Earth may not have plate tectonics (it is marginal in size for that), 5 times more and we may not have continents.
This has worried me re exoplanet habitability. Note that this is relatively dry, since most asteroids, pristine chondrites, have 15-20 % of water. But now it seems like a generic result of how terrestrials aggregate.
It also predicts how that water/hydrogen is internal but enough to explain Earth’s oceans by volcanism. No later impactors needed to provide volatiles.
Terrific news!
Also on Mars habitability: even this small amount of water makes the mantle malleable, see the point on plate tectonics. So Mars could have an active geology longer, with all that implies for life.
Well… at the very least, it is reassuring to note that there IS a source of carbon available for possible life?
I think that’s what the researchers wanted to get across: that carbon is being formed on Mars and carbon is a prerequisite to the formation of life as we know it. To me, the more carbon there is on a planet the better, as that means more of a chance for that one magical spark to happen at some point.
Of course there are carbon on Mars, the atmosphere is carbon dioxide and martian meteorites like ALH84001 with their carbonates confirm there is or was a carbon cycle with the crust. The question is if the PAH (polyaromatic hydrocarbons) were produced only in the meteorites, say at impact, as asteroids and comets also contain them.
Far easier to accept that Mars contributed to the PAH assembly.
But with only the abstract available outside the paywall I don’t know what they mean with “tectonic activity similar to Earth”. Mars has geologically recent volcanoes, signs of geologically recent magma in the meteorites and even signs of _historical_ landshakes. One mechanism isn’t threatened by having alternatives, nor is it strengthened by doubting these.
The better evidence is that some of these materials, whether oxides, macromolecular carbon or reduced PAHs, were “included within high-temperature minerals”.
Strangely, in the press release itself it didn’t mention much about the tectonic activity hypothesis. That was mentioned in the LiveScience article quoted at the end of the story. It also brought up the question in my mind of whether this process is still going on, as I’ve always though Mars was a dead planet geologically. Are there even any active volcanoes on Mars anymore?
No, the question is Mars has a convective core and hence can maintain active volcanoes is still an open question. I’m pulling this from memory, so YMMV:
– The differently aged shergottites, martian meteorites like ALH 84001, shows a sustained magmatic source all through martian history from ~ 4.2 billion years ago to some ~ 160 million years ago.
– The large volcanes have been crater dated to having lava flows to ~ 100 million years ago. I think.
– And recently they discovered rock falls from landshakes that are ~ 100 000 years old. As I remember it.
So there is a definitive sustained heat source, and it would be unlikely to have ended at the time we start to look for it.
This is by the way why Opportunity took geopositional measurements this martian winter. It is a sustained effort to establish whether Mars has a liquid core from its orbital movements. The experiment managed to raise beyond the precision of the previous data with a factor of 2, but I think as those researchers predicted beforehand they will need another winter to resolve the issue. Hopefully they will get it.
The article is a nice complement to this context, as all observed organics can still be explained by currently known martian geology (eventual methane from serpentinization, PAH from early volcanism).
While I appreciate the science of going to Mars (I love the red planet) I really would love for their efforts to be spent on other moons of Saturn and Jupiter. We’ve gone to Mars for 40 years and have found very little supporting evidence. Unless Curiosity finds something, that must certainly be a stamp for Mars not supporting life. Sorry if that sounds cynical, but It saddens me to see the other worlds of the Solar System ignored.
I agree wholeheartedly. I think the problem is two fold for the missions that you’re probably thinking about. 1) It’s alot harder to look the farther out you get in the solar system. Compared to dropping a lander/rover or two on a planet where we’ve already done it seems easy by comparison. 2) The time span it takes to get to some of the interesting moons is alot longer than even a mission to Mars, which makes it a little harder to convince the public that it’s worth it. I have a feeling that we’re going to start pushing that boundary soon though, especially if the price of getting to orbit drops as much as it could using commercial vendors.
The best option is for the next mission to Saturn to include a fly through of the Enceladus geyser plumes. The probe capsule which flies through this then makes a return trip to Earth. If these Jovian and Saturnian moons with subsurface oceans harbor life this seems to be the cheapest and simplest way to put it to the test.
LC
We have two efforts here, the public wants to know if there is or was life, and the science trying to establish it.
The Vikings were based on the premise “let us look for current life best we can – oh, and water too”. And it failed, miserably.
– The biological experiments were so bad you can just about predict their results by adding Phoenix data on perchlorates 40 years later.
– They missed digging to the underlying ice that Phoenix confirmed with about 20 – 50 cm according to current modeling of the orbiter data.
After that, the scientists buckled down to systematically (as in “science” =D) establish current and previous habitability to see if you should invest in a prolonged effort to search for fossils or life. That means looking for water and organics first.
– The MERs showed that water has been present geologically.
– Phoenix established both current water (ice) and by fortunate circumstances shored up the idea of current near surface liquid water (brine).
– MSL will try to find organics or at least look for the preservation conditions for them (clays).
Almost all astrobiologists think, what I know, that if MSL is successful, they can start look for biomarkers in earnest, and that the only way to find them would be sample-return. Because you need to do analysis building on what you find as you go, and the needed instruments (TEMs, accelerators for minute trace amounts) are huge.
You will probably need quite many sample return, inclusively a few drill riggs that are capable to go 100 – 1000 m down to the water table under the ice (if there is one). And those would mean with near future technology still having people in the loop as in deep water riggs. You can place those on Phobos, no need for landing.
But that is probably what it takes to test whether life was or is present on Mars. The only place there you may not need to drill is Enceladus or possibly Titan, but chances are you need it there too.
Mars is easier. And it will take many decades of work, unless we are very lucky. Which unfortunately in the current operation regime of an economical bottleneck, means it can go on for centuries – or more likely peter out without a definitive answer as people get tired of the investments. We will likely establish exoplanetary life (oxygenated habitables) before testing the remaining planets in our own system.
Don’t take me wrong though, I still think one offs like the Vikings or an Enceladus plume sample return would be well spent money to test our luck. The problem is to think that “that is it”. No, it isn’t, more likely it takes work.
“The biological experiments were so bad you can just about predict their
results by adding Phoenix data on perchlorates 40 years later.”
What was so bad about them? Do you question the credibility/integrity of
great scientists like Vance Oyama (NASA Ames) or Norman Horrowitz (Caltech)
who designed the experiments? 😉 Levins method for the LR – radio respiration for detection of microbial metabolism (which was invented by him) is commonly used on Earth as well like in the following example of use in extreme environments not unlike Mars:
http://www.ncbi.nlm.nih.gov/pubmed/17942178
But seriously what specific results of the BIOLOGY experiments could have been predicted by perchlorate? Perchlorate actually seems to have spoiled the GC/MS (none-)detection of organics which was the main objections against a biologic interpretation of the positive biology experiments (LR and partly PR).
Hint: If the active agent which produced the response in the active LR experiments would have been perchlorate it would have caused a positive response in the control runs too which didn’t happened!
“The Vikings were based on the premise “let us look for current life best we can – oh, and water too”. And it failed, miserably.”
It failed by having a positive response (LR), another partly/weak positive response (PR) and last an enigmatic response which was classified as a negative by mission protocols? Whats that for a science? I would call that exciting and most worth of following up!!! Where the scientific curiosity? Actually we wise earthlings still have no clue other than a lot of speculations about mysterious chemical oxidizers about the active agent(s) of the Viking biology experiments decades ago…
The premise “lets look for current life” is based on our experience on Earth that it is much easier to look for extant life (by monitoring its activity eg. respiration) which is in every inch of the surface than extinct life (fossils) on a big planet which is a rather big dusty wasteland in case of Mars.
– The series of experiments failed because they were inconclusive.
That result was easy to predict beforehand. They wanted to detect heterothrophs which needs a fairly large ecosystem with autothrophs in the bottom. So you need to detect organics too, which the heterothrophs should live of. If they didn’t detect the latter, the whole series of experiment would be inconclusive, and could even be contradictory.
That is what happened.
Heterothrophs are the result of a long evolution and complex ecologies, so I think it was a stretch to look for them in the first place. More likely it seemed to be an “easy and conclusive” experiment to the mission.
– The perchlorates explains why you can’t detect organics with any method that involves heating, as the GC/MS vaporization scheme used up until Phoenix. (Btw also possible to predict in principle, but hardly likely.)
This explained why the martian soils appeared to contain less organics than Moon rocks, and why it looked like cleaning agents were present in the chambers.
– I already commented on why “lets look for current life” was replaced by methodical investigation after the Viking debacle.
Are you sure you understand the full approach of Viking? Your statement “They wanted to detect heterothrophs” is wrong! All three biology experiments aimed for different kinds of life:
PR (most tests positive for life by missions protocols): photosynthetic life (as a base for other life?)
LR (ALL tests strong positive for life by mission protocols): more or less the other way around – heterotrophs
GEx (very strong mixed activity – inconclusive/negative by mission protocols): generic life which alters the composition of the surrounding atmosphere
Again all experiments had strong activity in the soil which still can not be fully explained by inorganic chemistry alone. Honestly, these results – at the very very least – would scream for follow up experiments like a chiral version of the LR. In the end its about whether or not there is life out there – one of the most intriguing questions of our times.
Only in an ideal world you would get a fully conclusive result in the first try on such complex topics so did they really expect such in the 70’s? But trying only once and packing/ignoring away the results is bad or pussies science!
Are you sure you understand the full approach of Viking? Your statement “They wanted to detect heterothrophs” is wrong! All three biology experiments aimed for different kinds of life:
PR (most tests positive for life by missions protocols): photosynthetic life (as a base for other life?)
LR (ALL tests strong positive for life by mission protocols): more or less the other way around – heterotrophs
GEx (very strong mixed activity – inconclusive/negative by mission protocols): generic life which alters the composition of the surrounding atmosphere
Again all experiments had strong activity in the soil which still can not be fully explained by inorganic chemistry alone. Honestly, these results – at the very very least – would scream for follow up experiments like a chiral version of the LR. In the end its about whether or not there is life out there – one of the most intriguing questions of our times.
Only in an ideal world you would get a fully conclusive result in the first try on such complex topics so did they really expect such in the 70’s? But trying only once and packing/ignoring away the results is bad or pussies science!
Actually the longer i studied Viking the more angry i was getting…
Well, dude, that’s your problem – you’re letting your emotions (double posting is one indication of that) cloud your logical judgement!
Yes, sorry for the double posting. Was more of a technical glitch than emotions but never mind: don’t worry about my logical judgement – the emotions are long gone (studied the Viking mission for a long time already) and I look forward to the flight data of that odd uncurious-curiosity rover with some neat contamination issues 😉
This is what ESA scientists thinks about the Viking mission results: “Numerous attempts have been made in the laboratory to simulate the reactions observed by the Viking biological package. While some have reproduced certain aspects of the data, none has succeeded entirely. Incredibly, almost 30 years after Viking, the crucial chemical oxidant hypothesis remains still untested.”
http://www.esa.int/SPECIALS/ExoMars/SEMK39JJX7F_0.html
@Mr. Larsson: Not the Viking mission and results was a debacle but maybe the conclusions derived from it with the result of retreating to geology missions only – so you may be right at a certain aspect 🙂