Well mars has a semi-molten core, and there are reasons to believe that there are deep volcanic activity still happening. It has even been suggested that a few of the viking images show volcanic steam venting...
Theres a nice image here:
http://mysite.freeserve.com/blobrana/cefoss.jpgThat shows the source of a water flow...the line of `dots` are probably a natural aquifer that is/was sitting above a thermal heat source...
The question is when the heat source cooled...(or if)...
And perhaps their metabolism has adapted, so as not to require an external heat source...Even at minus 120 degrees chemical reactions stall take place (slowly)...
UPDATE on Meeting:
NASA's associate administrator Ed Weiler accompanied by the mission's top geologist Professor Steve Squyres will attend the press conference at 1900 GMT.
Visual inspection indicates that the region's spherules are made of different material than the matrix rock. The layered rock is tan, while the spherules are gray.
The bulk, or "matrix," of the rock, is composed of very thin layers. The spheres, or "spherules," embedded in the matrix, are about half a centimetre.
One theory about the origin is that the spherules are "what geologists call concretions." Concretions form when water flows through a rock, carrying tiny bits of dissolved sediment along with it.
The sediment "precipitates around a nucleation site, and it grows these little spherical granules within the rock."
But then again it could have been the discovery of a jaw bone that swayed the balance: see `rock` near upper right , next to the skullcap...
http://marsrovers.jpl.nasa.gov/gallery/all/2/n/036/2N129563086EFF0361P1635R0M1.JPG :insane: