Mars Had Big Rivers For Billions of Years, Study Suggests

A new study suggests that Mars once had giant rivers larger than anything on Earth after the planet lost most of its atmosphere to space. 'That great thinning, which was driven by air-stripping solar particles, was mostly complete by 3.7 billion years ago, leaving Mars with an atmosphere far wispier than Earth's,' reports Space.com. 'But Martian rivers likely didn't totally dry out until less than 1 billion years ago, the new study found.' From the report: 'We can start to see that Mars didn't just have one wet period early in its history and then dried out,' study lead author Edwin Kite, an assistant professor of geophysical sciences at the University of Chicago, told Space.com. 'It's more complicated than that; there were multiple wet periods.' The team's work suggests that Martian rivers flowed intermittently but intensely over much of the planet's 4.5-billion-year history, driven by precipitation-fed runoff. The rivers' impressive width -- in many cases, more than twice that of comparable Earth catchments -- is a testament to that intensity.

It's unclear how much water Martian rivers carried, because their depth is hard to estimate. Determining depth generally requires up-close analysis of riverbed rocks and pebbles, Kite said, and such work has only been done in a few locations on Mars, such as Gale Crater, which NASA's Curiosity rover has been exploring since 2012. The ancient Mars rivers didn't flow in just a few favored spots; rather, they were distributed widely around the planet, Kite and his colleagues found.

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