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Dynamic Sand Dunes on Mars

Melting sand dunes on Mars. Photo credit: HiRISE, MRO, LPL (U. Arizona), NASA

Atmospherically speaking, there are some striking differences between Earth and Mars. The Martian atmosphere is thinner, about one percent as dense as Earth’s, and host high speed winds – the type that erode land to form surface features – fairly infrequently. It came as a surprise this week when scientists studying images from NASA’s Mars Reconnaissance Orbiter found that the sand dunes on Mars show the same level of activity as their Earthly counterparts. 

For years scientists have debated whether or not the sand dunes on Mars are a fossilized record of a past climate or something difference. This new evidence suggests the dunes are very active on the red planet.

The discovery comes from a comparative study of images. In 2007 and 2010, MRO’s High Resolution Imaging Science Experiment (HiRISE) camera took photographs of the Nili Patera sand dune field located near the Martian equator. These images were run through a software program designed to track the movement of sand ripples on dunes. The analysis showed scientists that ripples on top of the dunes move faster than those at the bottom.

This is a perspective view of the Nili Patera dune field. A HiRISE image has been draped over a digital elevation model of Mars. Image credit: California Institute of Technology

This means that the dunes are not only moving, they’re moving as huge, cohesive units across the Martian landscape. And it’s a lot of sand that’s moving. Scientists calculated that within a yard-wide area, about two cubic yards of sand would pass through the area in an Earth year. That’s about what you would find in a typical kindergarten sandbox.

It’s an exciting discovery that will help scientists understand the changing surface conditions on Mars on a planetary scale. “This improved understanding of surface dynamics will provide vital information in planning future robotic and human Mars exploration missions.” said Doug McCuistion, director of NASA’s Mars Exploration Program in Washington.

“We chose Nili Patera because we knew there was sand motion going on there, and we could quantify it,” said Nathan Bridges, a planetary scientist at Johns Hopkins University Applied Physics Laboratory. “No one had estimates of this flux before,” said Bridges. “We had seen with HiRISE that there was dune motion, but it was an open question how much sand could be moving. Now, we can answer that.”

The impact of the discovery is significant. The pace at which the sand dunes appear to be moving is more than what would be needed to erode rocky Martian features. “Our new data shows wind activity is indeed a major agent of evolution of the landscape on Mars,” said Jean-Philippe Avouac of Caltech. “This is important because it tells us something about the current state of Mars and how the planet is working today, geologically.” The dunes on Mars are similar to those found around Antarctica. Scientists estimate that the rocks in Nili Patera could be worn away at the same pace as rocks near sand dunes in the southernmost points on Earth.

These new results will also help scientists understand the broader mysteries of Mars, like why the surface shows so much erosion, how this happened, and whether it’s an ancient or more modern change. At least part of this mystery is solved since sand flux is certain to be one mechanism still shaping the Martian landscape today. Even if there isn’t life on Mars, it’s still a dynamic and fascinating world to discover.

 

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