The researchers, led by Seth Kadish and James Head from Brown University, said pedestal craters are characterized by a crater perched near the center of a pedestal -- a mesa or plateau -- that's surrounded by a roughly circular scarp rising from tens to more than 328 feet above the surrounding terrain.
Kadish and his team analyzed 2,696 pedestal craters on Mars at middle and low latitudes and discovered several had pits in their marginal scarps, similar to sublimation depressions seen on Earth and elsewhere on Mars. The pits, the scientists said, suggest pedestals formed from impacts into a volatile-rich substrate.
"Sublimation of the intervening volatiles then lowered the elevation of the surrounding terrain, except where inhibited by the impact-hardened surfaces, yielding perched pedestals," the researchers said.
From that, the scientists posit pedestal craters represent the armored remnants of an extensive, ice-rich climate-related deposit that existed during a substantial part of the recent past.
The research that included Nadine Barlow of Northern Arizona University and David Marchant of Boston University appears in the journal Geophysical Research Letters.
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