For the last 40 years, since the valleys of Mars were first discovered, the assumption has been that precipitation and surface water runoff fueled rivers that once flowed on Mars, eroding the landscape and forming all of these valleys. But there are dozens of valley networks on Mars and thousands of valley systems, and they look very different from each other. If you look at Earth from a satellite, you see a lot of valleys as well — some of them made by rivers, some made by glaciers, and some made by other processes, and each type has a distinctive shape. Mars is similar in that its valleys look very different from each other, suggesting that different processes acted to carve them.
According to new research led by Anna Grau Galofre at the University of Brithish Columbia, a large number of the valley networks scarring Mars’ surface, especially in the southern highlands, were carved by water melting beneath glacial ice, not solely by free-flowing rivers as previously thought. The similarity between many martian valleys and the subglacial channels on Devon Island in the Canadian Arctic motivated the authors to conduct their comparative study. They analyzed more than 10,000 martian valleys using a novel algorithm to infer the underlying erosion processes acting to form these valleys. Results of this analysis provide strong evidence for extensive subglacial erosion driven by channelized meltwater drainage beneath an ancient ice sheet on Mars. These findings help explain how the valleys could have formed 3.8 billion years ago on a planet that is further away from the Sun than Earth, during a time when the Sun was less intense. Climate modeling suggests that Mars’ ancient climate was much cooler during the time of valley network formation. Interestingly, these environments could also provide better survival conditions for possible ancient life on Mars. A sheet of ice would lend more protection and stability to underlying liquid water, as well as provide shelter from solar radiation. READ MORE