Washington, August 26 : A new study has suggested that eroded gullies on the flanks of a Martian crater may have been carved by flowing meltwater later than previously thought, as recently as a few hundred thousand years ago.
Evidence presented at a meeting in May this year had supported the theory that Mars gullies were created by melting snow, but didn't suggest a specific date.
Other scientists examining similar gullies in other craters had hypothesized that they might have been formed by dry avalanches or seepage from springs.
According to a report in National Geographic News, the new study used the latest high-resolution photos and technology from orbiting satellites to observe the gullies' geological setting.
They found that the gullies originate from cirque-like depressions high on the pole-facing slopes of the crater-depressions created by long-gone glaciers.
These glaciers flourished when wobbles in the Martian orbital axis caused the planet to tilt more strongly than it now does, creating ice age conditions. When the tilt again changed, the glaciers' ice turned to water vapor, but the depressions lingered.
"Similar conditions can be found in Antarctica's Dry Valleys," said study co-author David Marchant, a planetary scientist at Boston University. alled "beheaded" glaciers, these features have debris-covered glaciers on the lower parts of mountain slope. But higher up, the glaciers have depressions as much as 160 to 250 feet (50 to 75 meters) deep where the ice has dissipated into water vapor.
On Mars, snow could have fallen relatively recently on the crater rim, drifting into the depressions.
"You don't need much snow to create a gully," said Marchant. "The little bit that falls is transported to favored areas. There it can melt. When it does so, it does so quickly and creates enough meltwater to carve gullies," he added.
"The slope and shapes of the debris fans at the base of the gullies indicates that they are geologically quite young," said Marchant. "So, these things fit into a relatively young time on Mars history ... perhaps even almost up to the present," he added.
According to Marchant, thus, Mars is by no means a dead planet. "It undergoes climate cycles much like Earth," he said.