humans have sent many probes towards Mars, some succeeding, some not. the main reason for most of these missions, at least of late, is to find life on Mars, or the evidence that life once existed there. other reasons include looking for water, in the form of ice, and to see if it really is feasible for humans to one day inhabit it.
though the discovery of life on Mars, or the evidence that life once existed on Mars, would be heralded in the newspapers and by most scientists, it could very well be a death knell for humankind (and is certainly something i hope never happens). why?
the Great Filter is why.
10 years ago, Robin Hanson wrote a very compelling article titled, The Great Filter -- Are We Almost Past It?, we he theorizes that life continues, evolutionarily, to fill each ecological niche, and with consciousness and technological advances, humans have done the same. the ultimate end being extra-terrestrial colonization. however, if this colonization is the result of life, and life is so abundant in our universe (as it is typically hypothesized to be), then where are they?
this Great Silence must be explained. one explanation is something called the Great Filter: either one or many very improbable steps that the evolutionary path must take to go from the building blocks of life to colonization.
the crux of the issue is this: if we find NO life anywhere else, it's likely that we've already made it through the Great Filter, having been VERY lucky and fortunate to have done so (obviously). but, BUT, if we do find life elsewhere, no matter how simple, and if we don't encounter any other sentient beings who've colonized other planets, then it's likely we've yet to reach the Great Filter.
it's a very sobering read.
two other articles about the same thing are here and here. (NOTE: the last one is a pdf of Nick Bostrom's great article that appeared in the MIT Technology Review.)
so, here's to hoping Spirit, Opportunity and Phoenix find nothing more than ice, iron oxide dust and basaltic rock.