> There are good arguments either way. I predict that we will find extant
> microbial life, but that's just me. What's truly fascinating, ironically
> enough, is the potential of finding a _dead_ biosphere. Mars wasn't always
> steady-state...
If life did get started on Mars, it will be likely that it isn't completely "dead". They just recently isolated the protein that bacteria manufacture to put themselves into "stasis". The suspicion is that it forms a structure similar to ferritin, that sequesters iron molecules on the inside and forms a core around which DNA can crystalize on the outside (similar to histone molecules in eukaryotic cells). Given the rather harsh conditions on Mars, one would expect similar "preservation" mechanisms should have evolved there as well. Assuming a non-trivial biomass that may have gone underground with the water, it is likely to still be there in a "frozen" state. Radioactivity will gradually wear away at crystalized DNA, but if you had sufficient numbers when the conditions really harsh it is likely that somewhere there should still be viable organisms.
Robert