Back in March it was reported that a team of Russian scientists had broken through the Antarctic ice and exposed a lake that had been cut off from the surface for perhaps 15 million years. Reports as recently as July suggested that they did in fact find life, although apparently life within the lake and life outside the lake haven’t diverged very much in 15 million years of isolation. (That, or those ‘ordinary’ organisms were contaminants)
Anyway, this makes me worry about the possibility of life on Mars, for one very big reason: If life on Earth exists basically everywhere, from deep under ground to stuff floating up in the atmosphere, from deep-sea vents to the tops of mountains… Looking at the Earth, it seems like if life exists, it will eventually take over the entire planet. Ergo, if Mars had life, it should have reached the surface… but we don’t see any, in at least the regions we’ve rolled around.
Really, for me to hold out any hope of finding life on Mars, I’d need to know of at least one spot on or in the Earth in which there is NO life. Although, actually, there is one: the Atacama desert apparently has regions where there is no life at all, thanks to some combination of extreme altitude, dryness, and soil acidity (http://www.newscientist.com/article/mg19426082.100-the-last-place-on-earth-without-living-things.html) Let’s hope that the Atacama really is like the surface of Mars, otherwise Mars could turn out to be one heck of a barren place.