In recent years, it has become more and more evident that Mars once had liquid water on its surface. Images from rovers and orbiting cameras like those on Mars Reconnaissance Orbiter show all the same features that we see in formerly wet deserts here on Earth. These streambeds, river deltas, and other features make it clear Mars had water, but what they don’t tell us is if Mars was an icy world that periodically got above freezing or a lush world that lingered above freezing. To figure this out, scientists need to find the kind of evidence that gets left behind by glaciers, and that evidence has now been found. 

In a new paper in the Planetary Science Journal, researcher Ben Boatright describes a crater discovered to have geologic formations on the crater floor that point to streams and ponds forming. This isn’t unusual. What is unusual is the lack of evidence of a river or stream flowing into the crater to feed those water systems. Instead, they see the characteristic groves of a glacier that has been melting. This paints a picture of an ice age Mars that sometimes got above freezing, allowing glaciers to melt and feed hydrologic systems in craters like this one. While this paper only looks at one crater in great detail, Boatwright has another forty craters he’s studying that show similar features.

More Information

Brown University press release

“A Noachian Proglacial Paleolake on Mars: Fluvial Activity and Lake Formation within a Closed-source Drainage Basin Crater and Implications for Early Mars Climate,” Benjamin D. Boatwright and James W. Head, 2021 March 12, The Planetary Science Journal