Interesting that Gale Crater is about the same age as the oldest known fossils on earth. - http://www.sciencedaily.com/releases/2011/08/110821205241.htm
Life at that time was believed to be using sulfur instead of oxygen.
"Gale Crater, field site for the 2011 Mars Science Laboratory rover Curiosity, is located in one of the most chlorine- and sulfur-rich areas detected by Odyssey gamma-ray spectroscopy (GRS) along the dichotomy boundary between Mars' southern cratered highlands and the northern plains." - http://adsabs.harvard.edu/abs/2011AGUFM.P32A..04V
It begs the question, could Gale Crater(96 miles in diameter) be the origin of life on earth?
The impact was big enough, it would seem.
"A very recent and interesting analysis by H.J. Melosh at the University of Arizona shows that in the course of generating a l00-kilometer impact crater, debris can be transferred from Mars to Earth or vice versa" -
Sulfur loving life on earth is enduring, but it's not very diverse. There's not enough sulfur.
On Mars, a sulfur based life form could still endure, but it would likely stay in the water, and below ground, but that's not very exciting.
What would be exciting, is if you could find the source of that methane, and it's diverse.