HUGE glaciers may once have crept through Mars' version of the Grand Canyon. That's according to new analysis of data from NASA's Mars Reconnaissance Orbiter (MRO) spacecraft, which has spotted telltale signs of minerals left in the glaciers' wake.
Rock formations around Valles Marineris, a system of canyons running more than 4000 kilometres across the Red Planet's equator, have hinted that it once held glaciers that melted and caused a megaflood. Now Selby Cull at Bryn Mawr College in Pennsylvania and colleagues have found mineralogical evidence that supports the idea.
The team used spectral measurements from MRO to identify a number of minerals in the canyon, including jarosite, which forms in the presence of acid and sulphur. These deposits were spotted halfway up the canyon walls, so can't have been left by an evaporating pool of water, which is how other jarosite deposits on Mars are thought to have formed.
Instead, Cull speculates that heat from the walls could have slightly melted the ice, which in turn reacted with sulphur in the planet's earlier atmosphere.
"The glaciers would have been interacting with the side of the canyons, producing acid melt water," she says. A similar process has been observed on Earth at the edges of the Svalbard glaciers in Norway.
Journal reference: Geology, DOI: 10.1130/G36152.1
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