Wed 6 Dec | Space.com
A new Brown study found that ancient Mars may not have been all that warm and wet after all. The Red Planet has widespread deposits of clay minerals, which are formed via the interaction of volcanic rock and water. This fact has led some researchers to suspect that liquid water covered much of the Martian surface for extended stretches long ago — perhaps during the Noachian period, which lasted from about 4.1 billion to 3.7 billion years ago. But the new study suggests that these clays could have formed even longer ago, right after the planet's formation — meaning the Noachian may well have been a mostly dry and chilly time.