London, July 14 (ANI): A new study has suggested that craters embedded on pedestals that tower above the Martian landscape like giant egg cups could be used to trace the planet's climate.
'Pedestal' craters were gouged out by impacts, like other craters, but stand out because they sit atop plateaus that loom an average of 50 metres above the Martian surface.
It's not clear exactly how the pedestals formed.
According to a report in New Scientist, a comprehensive catalogue of the objects is lending weight to the idea that the pedestals may conceal ice-rich soil from previous eras, when the planet's spin axis tilted at a different angle than it does today.
Seth Kadish of Brown University in Providence, Rhode Island, and colleagues identified 2696 pedestal craters in the planet's mid- and low-latitudes from images taken primarily by the thermal imager aboard NASA's Mars Odyssey spacecraft.
The craters seem to be concentrated at the mid-latitudes, with very few found at the planet's equator.
About 3 per cent of them have depressions around their bases that resemble areas in Antarctica where permafrost ice vaporizes, creating pits in the soil left behind.
The team said that strengthens the hypothesis that the pedestals were created from soil that was enriched in ice during a period when the Martian poles pointed more towards the sun and its mid-latitudes were colder.
Because Mars does not have a massive satellite that stabilises it, like Earth's moon, the tilt of its axis is thought to change regularly on scales of tens of thousands of years.
When the planet is tilted most drastically on its side, the planet's poles receive a lot of sunshine. Any water locked in ice there is thought to vaporize and move towards the equator, where it falls as snow.
Tens of metres of snow are thought to be deposited on the planet's mid-latitudes during these episodes.
Pedestal craters may preserve regions with this ancient snow.
The researchers suspect the impact of the meteorite that created each pedestal crater could somehow 'armour' the ground in the area, producing a top layer that protected ice from sublimating into gas during warmer periods.
The unprotected ice surrounding the armoured area, however, would eventually disappear when the planet's tilt changed and the area warmed.
That would leave behind the modern-day, ice-laden pedestals that can be more than 100 metres thick.
"These pedestals represent almost like a cookie-cutter section of past icy, dust-rich layers," Kadish said. (ANI)