Mars Ocean

Artist's rendering of what Mars may have looked like with an ocean, billions of years ago. For decades, planetary scientists have suspected that ancient Mars was a much warmer, wetter environment than it is today, but estimates of just how much water Mars has lost since its formation vary widely. Measurements by researchers at NASA have revealed that an ocean once covered approximately twenty percent of the Martian surface. This new view of early Mars is considerably wetter than many previous estimates, raising the odds for the ancient habitability of the Red Planet.

Image credit: NASA's Goddard Space Flight Center