Science -- Solomon et al. 307 (5713): 1214:
What is emerging from a better understanding of the early history of Mars is that the Noachian was a time when hydrothermal systems capable of fostering organic synthesis and sustaining any life forms that may have occupied such niches were wide-spread and may have extended at least halfway to the base of the crust.
Remote sensing, recovered Martian meteorites, and Mars rovers, document the geological history of Mars, and uncover the possible early conditions of life on Mars. This is possible because geologists, exobiologists and astronomers rely on evolutionary biology to guide them.