Likelihood of confirming past life on Mars

[dilletante]

If there was microbial life on Mars in the distant past, would there be any way to conclusively confirm it? Or would any such attempt be reduced to speculation, like the Martian meteor which "possibly" contained evidence?

 

[mfb]

We can conclusively show that microbial life has existed on Earth about 3 billion years ago (paper). Therefore: yes, it has to be possible.

 

[rootone]

I believe the rover planned as a followup to 'Curiosity' will have some experiments aboard which would be more capable of detecting chemical signatures of life, Including biological activity in the past.
The current mission is primarily looking at geological features, which is a good place to start for getting an overall picture of the planet's history.
Absolutely conclusive evidence of life is going to require something like an indisputable fossil of some sort, or at least a hydrocarbon rich deposit.
It may be that we will have to wait for the rovers and orbiters to gather sufficient clues for an ideal site that future human explorers can investigate, and these would surely include experts in biology and related sciences.

 

[Chronos]

If martian life was significantly different from terrestrial life, it could be difficult to deduce it was living. Our knowledge of exobiology is extremely limited [as in nonexistent] at present. Knowledge in any new field of science is only reliable after extensive and intensive scrutiny. The truth is only that which remains after all reasonable alternatives have been eliminated.

 

[mfb]

The NASA rovers are not sterile - which also means they stay away from the most likely places to find life today. That makes every possible discovery of cell-like structures and chemical evidence problematic, as we would need additional evidence that it does not come from Earth.

 

[rootone]

Which when considered this leads to an even more difficult problem.
While robots can in principle be sterilized, human explorers can't be.

 

[mfb]

Human explorers would probably use better equipment to test the samples, and return some of them to Earth for an even more thorough investigation.