How to actually look for life on Mars

[NERVAfan]

We haven't actually looked for life on Mars since the Vikings (except for the failed Beagle 2) and the knowledge of microbiology was just really primitive back then. (They didn't even know about chemosynthesis when those experiments were designed.) They also didn't know about perchlorates in Martian soil.

So here's what I think we should send to Mars next...

A lander (doesn't even necessarily need to be a rover - this could basically be "Viking updated" - though a rover would be better) with the following instruments:

To look at rocks in-situ/"in the wild":

-Microscopic imager to look for microfossils.

To extract samples:

-Digging tool to get soil from at least a meter or so down.

-Drill to extract samples from the interior of rocks (to look for endolithic microbes)

To analyze samples:

-Raman spectrometer to look for organic molecules/biomolecules. Curiosity's SAM instrument has had problems due to contamination, but IIRC also since it has to heat a sample to analyze it, and Martian soil has perchlorates in it, which react with the organics when heated. (ExoMars rover is going to have one of these... but I am not optimistic of its getting a chance to be used since ESA has outsourced the launch and landing system to Russia, who have a very bad Mars record.)

-Metagenomics experiment. Oversimplified, this is basically "grab an environmental sample and analyze any DNA in it". This has been a huge development in microbiology; before, we were basically limited to studying cultured microbes, and we couldn't culture most microbes!

[KerikBalm]

The metagenomics experiment presupposes the life would be DNA based, and using the same 4 basepairs.

We already have strong evidence of RNA only life in Earth's history, and there are extand RNA genomes (only in viruses though)

If it works, it either means there was at least limited panspermia within the solar system, or certain biochemistries are heavily favored - which may be the case, seeing as how we see amino acids and PAHs (precursors to nucleic acids) out in space already.

If it is a case of limited panspermia, it would be very hard to prove it wasn't contamination that came with the probe.

[NERVAfan]

The metagenomics experiment presupposes the life would be DNA based, and using the same 4 basepairs.

Well, it's more to determine IF it is, since there's the possibility of transmission of life from Earth via meteorites.

If it works, it either means there was at least limited panspermia within the solar system, or certain biochemistries are heavily favored - which may be the case, seeing as how we see amino acids and PAHs (precursors to nucleic acids) out in space already.

Yes, exactly.

If it is a case of limited panspermia, it would be very hard to prove it wasn't contamination that came with the probe.

No, tis is exactly what the metagenomics experiment resolves! If it is contamination, it will be something we know about or at least a very close relative of something we know about. If it uses our genetic system but is distantly related, then it was transmitted naturally a long time ago.

I suppose there could be some ambiguity if it arrived by meteorite very recently... but that seems very unlikely since life has existed on Earth for ~4 billion years and there were more big impacts early on. I doubt there's been any impacts big enough to eject significant rocks to escape velocity in the last few million years (the K-T impact might have, but 65 million years allows significant evolution).

[Yakuzi]

Great thread and ideas! The metagenomics module could provide reliable results with the appropriate negative control tests pre- and post sampling, but like Kerikbalm mentioned, this would be under the presumption that Martian life would be DNA/RNA based.

Still, it would be interesting to have such a device onboard.

Additionally, an instrument to check for metabolites and turbidity in a series of sterile nutrient broths (including suspended autoclaved local materials) inoculated with martian samples would be great. However, as mentioned in the OP, many microbes on earth are not cultivatable and we would have to know what metabolites to screen for. Methane would be a start:

http://metro.co.uk/2014/12/16/nasa-rover-finds-possible-signs-of-life-on-mars-4990114/

Microscopic analysis would definitely be interesting, particularly if we can thaw some polar or underground water ice. Depending on the microscope type and resolving power, we should be able to identify microbial structures. However, if Martian cells are too small this may prove difficult with standard microscopes and I'm not sure sampling for EM can be automated and even if it could, we may not be able to establish whether we are looking at cells or abiotic mineral formations (as exemplified by the SEM micrographs from the J96 Martian meteorite that fell on earth).

One final thing to keep in mind. Even if we'd have an extraterrestrial organism right in font of our nose and would have every scientific piece of equipment at our disposal, we might still not be able to identify alien life, because... well, it might just be too alien

Edited December 17, 2014 by Yakuzi

[Frozen_Heart]

They seem to be building a rover based on curiosity. Just focused on biology though.

[Kryten]

They seem to be building a rover based on curiosity. Just focused on biology though.

The 2020 rover is intended to cache samples for future return-the focus for the instrument suite is to find the best samples. It has enhanced ability to detect organics as part of that, but just detecting organics in itself would test us very little about possible life. After all, given what we know about comets and C-class asteroids, Mars has to be being bombarded with organics all the time.

[Yakuzi]

The 2020 rover is intended to cache samples for future return-the focus for the instrument suite is to find the best samples. It has enhanced ability to detect organics as part of that, but just detecting organics in itself would test us very little about possible life. After all, given what we know about comets and C-class asteroids, Mars has to be being bombarded with organics all the time.

That's why checking in situ for respiration, motility and/or division might be preferential.

PS, is the the 2020 rover return mission operated by NASA? If so I'm predicting a hysteria session that will eclipse the recent ebola hype-train.

[Kryten]

The return mission is currently very much in flux (read: nobody wants to pay for it at this point), but would likely be a joint mission with another agency.

Edited December 17, 2014 by Kryten

[Aningaaq]

The 2020 rover is intended to cache samples for future return-the focus for the instrument suite is to find the best samples. It has enhanced ability to detect organics as part of that, but just detecting organics in itself would test us very little about possible life. After all, given what we know about comets and C-class asteroids, Mars has to be being bombarded with organics all the time.

But doesn't locating organics in a specific type of subsurface feature greatly enhance the potential for finding biosignatures in future candidate sites? If so, wouldn't Mars 2020 be a necessary precursor to a rover that looks for biosignatures?

[Kryten]

Finding biosignatures would be part of the job of the terrestrial labs analysing the 2020 rover samples. Otherwise we're running into instruments that are simply extremely hard to fit on a rover and within the power and data budgets.

[NERVAfan]

I'm kind of skeptical of finding biosignatures as such. It seems really a stretch that complex molecules would survive that long, even without Earth-style decomposers.

Microfossils are more likely (but those are rare even on Earth and would be hard to unambiguously identify).

I think looking for present life is key. (And if Mars ever had life at all, there's a pretty good chance it would have survived, IMO.

Great thread and ideas! The metagenomics module could provide reliable results with the appropriate negative control tests pre- and post sampling, but like Kerikbalm mentioned, this would be under the presumption that Martian life would be DNA/RNA based.

Still, it would be interesting to have such a device onboard.

Additionally, an instrument to check for metabolites and turbidity in a series of sterile nutrient broths (including suspended autoclaved local materials) inoculated with martian samples would be great. However, as mentioned in the OP, many microbes on earth are not cultivatable and we would have to know what metabolites to screen for.

Also, nutrient broths would probably only work if the lifeforms were 'organotrophs' - getting their carbon from previous biological sources. Since Mars probably doesn't have much of an ecosystem, it's pretty likely Mars life would just fix carbon directly from CO2 - it wouldn't necessarily be able to metabolize a nutrient broth.

Microscopic analysis would definitely be interesting, particularly if we can thaw some polar or underground water ice. Depending on the microscope type and resolving power, we should be able to identify microbial structures. However, if Martian cells are too small this may prove difficult with standard microscopes

You would at least have a good chance; I would think cell sizes would likely be comparable. They can only be so small before there simply isn't room to fit in the complex molecules... I think the smallest Earth cells (200nm-300nm) are too small to see well with light microscopes though, since this is less than the wavelength of visible light (~400nm-700nm).