Mars Landscape Bears Traces of Icy Past

May 20, 2008 -- A closer look at the remnants of mid-latitude glaciers on Mars has revealed signs of deep, icy rivers in the recent geologic past, say researchers who have published the discovery in the May issue of the journal Geology.

Mars glaciologist James Dickson of Brown University and his colleagues followed the trail of telltale glacial remnants at the edges of Mars' northern lowlands and were surprised to find signs that a glacier once traveled in a direction now uphill, toward a canyon's edge. Unless the glacier somehow defied gravity, the only explanation is that it was once higher than the canyon.

"What we see right now is a glacier that looks like it flowed uphill," Dickson told Discovery News. "That can't happen."

To make the features conform to gravity, the researchers imagined filling a neighboring valley with ice so high that it could then flow down toward this canyon. The current uphill appearance is the result of most of the ice evaporating away, leaving debris and the surface features seen today.

"We are very confident that there was a kilometer of ice at this location," said Dickson. Nearby lowlands would also have been filled with ice, in some areas two kilometers deep, he explained. The expansive ice sheet was perhaps comparable to what covered North America during the last Ice Age.

"They are pretty much on target," said Mars researcher Jeffery Kargel of the University of Arizona of the Dickson's conclusions. What's more, he said, there's no reason to believe all the ice is gone from these glaciers.