Mars Rover - Dumb Question

There is water on mars, it's all in the ice caps or underground (unknown) now but it flowed across the surface at some point and carved the great canals (canyons) of Mars. The Atmosphere is CO2 heavy iirc but that should be no problems for the sorts of microbes they are expecting to find, (if anything at all).

My point isn't so much is there water or Earth style minerals and gasses which could sustain life.
More is it possible that there are other life forms which would not require the same minerals, gasses that earth creatures need to survive?
From what you say it seems to suggest they are purely looking for anything similar to what might be found on earth(or atleast in what it needs to survive)?

No other element is as versatile as carbon so it's highly unlikely that there will be life based on another element. Possibly a different oxidising agent (other than oxygen) could provide energy. The carbon based life form using oxygen to get energy from carbon based food sources is pretty elegant and the most energetically favourable way of doing things, so it's pretty likely that any other life form in the universe will be chemically similar.

If carbon is so good, how come all aliens are silicon based life-forms?

hush, you; look into the bright red memory erasing light.

Hmmm ... I think that NASA, ESA, etc. are going with the "we're looking for life" line because it excites the masses (including me, I must confess). And while the search for extra-terrestrial life is an important mission for NASA, it's my understand that the current (and planned) Martian missions are more looking at what is present on the planet that can be utilized in developing future permanent Martian outposts (what we need to haul to the planet vs what we can monkey around with and make work for our purposes that is already on the planet). So they're doing the science thing, but what's being tossed out to the media isn't the whole story (er, and what the media is choosing to report isn't the whole story, either, of course).

An odd tidbit of information ... NASA's been under a hiring-freeze for some time (just NASA, not the contractors) ... the only positions that NASA is actively seeking applications for are in the field of astro-biology.

And yes, they're primarily looking at carbon-based life-forms at this point, but they're not at all disregarding other options. But, of course, then one runs into the sticky question of what constitutes life, how to communicate with a completely alien being, etc.