Yes - they could. But - need to search on Mars - I think ExoMars is on the right lines, searching in situ and digging deep.
Cosmic radiation would completely destroy - even a million tons of surface organics - so much you don't have a single molecule left after three billion years. It reduces amino acids a trillion fold every a billion years approximately (easy number to remember).
That's surface deposits. So they are looking for deposits buried quickly - and then brought to the surface again quickly. No good if it was buried slowly over a few million or billion years.
Meanwhile, Mars receives a constant influx of organics from micro-meteorites and meteorites. This would obscure any signal of ancient life.
On Earth it is obscured by more recent organics from life, by racemization because no samples on Earth have been kept cold for so long - and degradation by more recent life.
On Mars it is obscured by more recent organics from micro-meteorites, by radiation mainly.
We have already found organics -so next thing is to look for biosignatures. But Curiosity is not really equipped to do that. Nor is the follow up rover to Curiosity.
ExoMars is - and might well find them.
NASA don't really seem to be approaching this in the right way - seems to me - based on the findings of several notable exobiologists who are directly involved in the search for life on Mars.
They want to return a sample from Mars to Earth. But how is that going to help - unless they know what is in the sample already?
At millions of dollars per gram, just doesn't make sense to return samples to Earth to test to see if there are any biosignatures in the sample. Not when most such samples probably won't have any definite signs of life. And when we have a wide range of places to sample, can rove over many thousands of square kilometers on Mars looking for samples to analyse.
How can you return representative samples from thousands of square kilometers to Earth when you can only return hundreds of grams of material - and when you have no way of distinguishing between interesting and uninteresting organics on Mars?
To take an example - ExoMars may well visit Mawrth Vallis
The 4th MSL Landing Site Workshop: Day 2 - Mawrth
Do you see those layers - that's the reason it is of such interest - many of them clays, which are reasonably likely to preserve organics.
ExoMars - on the spot - can sample layers for organics. Then having discovered those - can then sample for biosignatures.
First biosignatures may be faint - just a few amino acids and a slight chiral imbalance because of severely degraded life. So at this stage is just a hypothesis.
So - ExoMars is on the spot - so you can command it to search that layer - take samples at different depths and do a more thorough investigation.
It might find that the signal remains weak - and is probably due to meteorite chiral imbalances (say). If so - then it would stop investigating that layer - or that part of a layer - and move on to another target.
In this way it can gradually home in on the sites in its target area with the strongest signals of possible biosignatures.
This would require dozens of sample returns from Mars, at huge expense, most of them returning samples that are of no interest for biology.
It is quite possible that a sample return from Mawrth Vallis would return no samples with any biosignatures in them at all. This would not mean that there is no life to be detected in Mawrth Vallis.
It would just mean that you haven't yet found life there. That's all. No way that a sample return can rule out or even significantly reduce probability of finding past life on Mars - and chance of it actually finding the life is also probably remote.
Is not just me saying that - but a white paper by 8 exobiologists submitted to the last decadal review.
They surveyed the issues in technical detail, and concluded that a sample returned from Mars is likely to be as inconclusive for biology as the Alan Hills meteorite which caused so much fuss a few years ago but proved nothing (so far anyway).
For some reason their findings were not mentioned or discussed in the decadal review summing up.
This is their paper if you want to know more about the technical details - why they think the time is not yet right for a sample return from Mars, for the search for life there.
SEEKING SIGNS OF LIFE ON MARS: IN SITU INVESTIGATIONS AS PREREQUISITES TO A SAMPLE RETURN MISSION
First, as we are doing with ExoMars, search for the biosignatures in situ on Mars.
Next is - are the biosignatures signs of life - or is it same as comets or meteorites?
Rosetta's study of the organics in a comet may help there combined with meteorite studies on Earth.
So far we'd know perhaps, with some confidence, that it is probably some form of life - if everything else is ruled out. But would be a long way from showing it is an ancestor to Earth life.
Indeed might be that all we know is that it was constituted of amino acids like Earth life. Might also have some more complex compounds such as Carotenoids (which happen to be particularly robust under cosmic radiation so may be easiest to spot).
After a while, looking at really ancient deposits - we might show that there is life on Mars before the impact of the Moon with Earth.
That would be enough to show that it predates Earth life. But not that it seeded Earth. Because - it could equally be that some other place seeds both Mars and Earth (e.g. Venus or embro planets, or the impactor that hit Earth or indeed the proto Earth before it was hit - sending debris into space after the impact).
Or life develops independently on each.
As for finding out details - that would be intricate detective work using severely degraded ancient organics.
It might help a lot there if we also have present day Mars life. If we can show it is related to Earth life - but not identical - that could help to trace back - and do a genetic profile of the last common ancestor of Mars and Earth life.
Though - if we found present day Mars life that is unrelated to Earth life - that would show that at least some life on Mars evolved independently of Earth (though it wouldn't rule out the possibility of other Mars life that seeded Earth).
So - I think - combination of past life, present day life, study of comets, study of meteorites - and a lot of detective work needed.
But - yes - could happen eventually. Probably some decades away to show for sure.
Cosmic radiation would completely destroy - even a million tons of surface organics - so much you don't have a single molecule left after three billion years. It reduces amino acids a trillion fold every a billion years approximately (easy number to remember).
That's surface deposits. So they are looking for deposits buried quickly - and then brought to the surface again quickly. No good if it was buried slowly over a few million or billion years.
Meanwhile, Mars receives a constant influx of organics from micro-meteorites and meteorites. This would obscure any signal of ancient life.
FIRST, NEED A CLEAR SIGNAL, BURIED QUICKLY, WELL PRESERVED FOR BILLIONS OF YEARS, UNEARTHED QUICKLY
- We need to find a place where there was life in the pasT
- Where it was buried quickly, and then froze quickly (if it was kept at liquid water temperatures with water flowing through it for significant periods of time - the ancient organics get washed out, and also chiral signature degrades through racemization)
- Was then unearthed quickly - or we are able to drill down to it - needs to have stayed below 10 meters of depth to avoid the worst of the cosmic radiation damage
- Retaining a clear biosignature.
On Earth it is obscured by more recent organics from life, by racemization because no samples on Earth have been kept cold for so long - and degradation by more recent life.
On Mars it is obscured by more recent organics from micro-meteorites, by radiation mainly.
We have already found organics -so next thing is to look for biosignatures. But Curiosity is not really equipped to do that. Nor is the follow up rover to Curiosity.
ExoMars is - and might well find them.
NASA SEEM TO BE ON THE WRONG TRACK HERE
NASA don't really seem to be approaching this in the right way - seems to me - based on the findings of several notable exobiologists who are directly involved in the search for life on Mars.
They want to return a sample from Mars to Earth. But how is that going to help - unless they know what is in the sample already?
At millions of dollars per gram, just doesn't make sense to return samples to Earth to test to see if there are any biosignatures in the sample. Not when most such samples probably won't have any definite signs of life. And when we have a wide range of places to sample, can rove over many thousands of square kilometers on Mars looking for samples to analyse.
How can you return representative samples from thousands of square kilometers to Earth when you can only return hundreds of grams of material - and when you have no way of distinguishing between interesting and uninteresting organics on Mars?
To take an example - ExoMars may well visit Mawrth Vallis
Do you see those layers - that's the reason it is of such interest - many of them clays, which are reasonably likely to preserve organics.
The next talk was by Janice Bishop who summarized the mineral diversity in the site. She showed a bewildering number of spectra from Mawrth, and drove home the fact that the mineralogy observed occurs in the same stratigraphic order all over mawrth and all over much of the Arabia Terra region on Mars, supporting the idea that understanding Mawrth would teach us about a huge section of the planet. One of the interesting things that Janice and others showed is that these compositional layers are observed in some layered rock in the floor of Oyama crater, the huge crater to the west of the ellipse. This is interesting because it is thought that the rocks in the ellipse are older than Oyama, and obviously the rocks filling Oyama are younger. The fact that they show the same mineral stratigraphy suggests that the related alteration came after the physical deposition of the rocks.NASA would approach this by returning 500 grams of samples from these rock formations. Obviously it can't sample every layer - just one sample from each of the layers they think are likely to be of most interest for biology. Layers that have organics obviously - but organics here doesn't mean life.
At the end of the discussion of Mawrth, I felt a lot better about the site than I did before going in. There is clearly a lot of good stuff to do there, and it has a couple of undeniable advantages: it is clearly the oldest site, and you get to land on your primary target. But I’m also concerned by what I hear from terrestrial geologists who are very concerned about how much Mawrth would actually tell us about the habitability of Mars. Yes, it has spectacular phyllosilicates, but it’s not clear that they would trap any organics since we don’t know what the depositional setting was. I think despite this uncertainty, if you polled the community, Mawrth would be one of the top two sites.
HOW A REMOTELY OPERATED FIELD TRIP ON MARS MIGHT PROCEED, SEARCHING FOR LIFE
ExoMars - on the spot - can sample layers for organics. Then having discovered those - can then sample for biosignatures.
First biosignatures may be faint - just a few amino acids and a slight chiral imbalance because of severely degraded life. So at this stage is just a hypothesis.
So - ExoMars is on the spot - so you can command it to search that layer - take samples at different depths and do a more thorough investigation.
It might find that the signal remains weak - and is probably due to meteorite chiral imbalances (say). If so - then it would stop investigating that layer - or that part of a layer - and move on to another target.
In this way it can gradually home in on the sites in its target area with the strongest signals of possible biosignatures.
This would require dozens of sample returns from Mars, at huge expense, most of them returning samples that are of no interest for biology.
It is quite possible that a sample return from Mawrth Vallis would return no samples with any biosignatures in them at all. This would not mean that there is no life to be detected in Mawrth Vallis.
It would just mean that you haven't yet found life there. That's all. No way that a sample return can rule out or even significantly reduce probability of finding past life on Mars - and chance of it actually finding the life is also probably remote.
Is not just me saying that - but a white paper by 8 exobiologists submitted to the last decadal review.
They surveyed the issues in technical detail, and concluded that a sample returned from Mars is likely to be as inconclusive for biology as the Alan Hills meteorite which caused so much fuss a few years ago but proved nothing (so far anyway).
For some reason their findings were not mentioned or discussed in the decadal review summing up.
This is their paper if you want to know more about the technical details - why they think the time is not yet right for a sample return from Mars, for the search for life there.
SEEKING SIGNS OF LIFE ON MARS: IN SITU INVESTIGATIONS AS PREREQUISITES TO A SAMPLE RETURN MISSION
HOW THE SEARCH WOULD CONTINUE AFTER THAT
First, as we are doing with ExoMars, search for the biosignatures in situ on Mars.
Next is - are the biosignatures signs of life - or is it same as comets or meteorites?
Rosetta's study of the organics in a comet may help there combined with meteorite studies on Earth.
So far we'd know perhaps, with some confidence, that it is probably some form of life - if everything else is ruled out. But would be a long way from showing it is an ancestor to Earth life.
Indeed might be that all we know is that it was constituted of amino acids like Earth life. Might also have some more complex compounds such as Carotenoids (which happen to be particularly robust under cosmic radiation so may be easiest to spot).
After a while, looking at really ancient deposits - we might show that there is life on Mars before the impact of the Moon with Earth.
That would be enough to show that it predates Earth life. But not that it seeded Earth. Because - it could equally be that some other place seeds both Mars and Earth (e.g. Venus or embro planets, or the impactor that hit Earth or indeed the proto Earth before it was hit - sending debris into space after the impact).
Or life develops independently on each.
As for finding out details - that would be intricate detective work using severely degraded ancient organics.
It might help a lot there if we also have present day Mars life. If we can show it is related to Earth life - but not identical - that could help to trace back - and do a genetic profile of the last common ancestor of Mars and Earth life.
Though - if we found present day Mars life that is unrelated to Earth life - that would show that at least some life on Mars evolved independently of Earth (though it wouldn't rule out the possibility of other Mars life that seeded Earth).
So - I think - combination of past life, present day life, study of comets, study of meteorites - and a lot of detective work needed.
But - yes - could happen eventually. Probably some decades away to show for sure.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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