A false-color image of dark sand dunes at high northern latitudes on Mars that are covered seasonally by a layer of condensed carbon dioxide (dry ice).NASA/JPL/University of Arizona
— During the spring, carbon dioxide changes from a solid to a gas with enough force to trigger small avalanches.
— Pictures taken over two Martians seasons show winds are strong enough to lift and move grains of sand.
— The studies will help scientists figure out what features on Mars were formed by processes that are no longer active.
Each spring, Mother Nature gives part of Mars a facelift using tools not available on Earth.
During winter, carbon dioxide condenses out of the atmosphere and forms a frost of dry ice that coats the planet's polar region. The subsequent spring-time thaw, apparently, is not a subtle affair.
Blasts of carbon dioxide gas escaping from the warming ground send sand cascading down dunes in the planet's northern polar region, an area previously believed to be unchanged and unchanging over time.
The field of dunes, which covers an area about the size of Texas, were photographed over two seasons by a high-resolution camera on NASA's Mars Reconnaissance Orbiter.
"I was hoping for tiny little changes to be detectable," planetary scientist Candice Hansen-Koharcheck with the Planetary Science Institute in Tucson, Arizona, told Discovery News. "This was more like knock-your-socks-off kind of stuff. It's a very active part of the Mars landscape in today's climate."
In one instance, scientists found that hundreds of cubic yards of sand had avalanched down the face of a dune.
They also found evidence that wind gusts in the northern polar region are strong enough to move grains of sand. "That was thought to be uncommon," Hansen-Koharcheck said.
Though Mars' atmosphere is very dynamic, its surface doesn't show change like Earth's.
"Erosion seems to be slower," said David Kass, a Mars atmospheric scientist with NASA's Jet Propulsion Laboratory in Pasadena, California.
Mars is a focal point in the quest to learn if life exists beyond Earth. The Mars Reconnaissance Orbiter is part of a fleet of satellites, landers and rover that have dispatched to the Red Planet for studies.
The research includes tracking climate and environmental processes active on Mars today, so scientists can figure out what might have been different in the past, when Mars was warmer, wetter and more hospitable for life as we know it.
"To see an active geologic process on Mars today is cool," said Hansen-Koharcheck.
Her research appears in this week's Science.