Billions of years ago, the planet Mars appears to have been covered by a liquid water ocean. Geologic evidence of riverbeds, deltas, canyons, and other features in the Martian landscape all suggest that a flowing liquid once meandered on the surface of the red planet. Even so, the fainter young sun at the time, combined with Mars’ orbital distance from the sun, suggests that even a wet early Mars was probably quite chilly.
In a recent paper published in Nature Geoscience, on which I am a co-author, we examine the idea that early Mars featured a cold glacial ocean on its northern hemisphere. This study combines some theoretical climate calculations (which was my contribution) along with a mineralogical analysis to reach this conclusion. In particular, the formation of minerals known as phyllosilicates would have been prevented in a cold ocean, which may explain the scarcity of phyllosilicates observed in the northern martian hemisphere today.
And if oceans did exist on Mars billions of years ago, then perhaps the processes of life also could have arisen in the early history of the red planet. Mars today appears barren and lifeless, but signs of past or present life could very well be lurking beneath the soil. Future Mars missions, and possibly human exploration, will eventually help to uncover this mystery.