Mars shifting sands revealed by long-term observations – Astronomy Magazine

(Inside Science) -- Martian megaripples might sound like they are straight out of science fiction. But they are real and just as fantastic as they seem.

Megaripples are sandy landforms, or bedforms, that rise 1 or 2 meters off the surface. They have been spotted all over the surface of the red planet from the mottled floors of craters to the undulating plains of sand dunes. Not quite as large as sand dunes, but also not as small as what scientists call large ripples, megaripples are the middle child of bedforms on Mars. Unlike middle children, however, they are big and bright enough to be easily spotted by satellites.

Most Martian sand dunes are made up of a large range of grain sizes and large ripples are composed only of tiny, finer grains. Megaripples, on the other hand, are made of fine-grained sands at the bottom and coarse-grained sands at the top, making them less mobile by the weak Martian atmosphere. This has prompted scientists to assume that they are remnants of a past environment when the wind was stronger. But now, after a decade of observation, planetary scientists have used images from the High Resolution Imaging Science Experiment (HiRISE) to show that these megaripples are actively moving.

"We had the opportunity to see these megaripples moving because now we have more than 10 years of observations,"said lead author Simone Silvestro, a planetary scientist at the National Institute for Astrophysics Astronomical Observatory of Capodimonte in Naples, Italy. As HiRISE continues to photograph the Martian surface, the repeated observations reveal processes that were once thought to be dormant.

"It isnt like Mark Watney getting blown away from the other astronauts in 'The Martian,'"said Matt Chojnacki, co-author and associate staff scientist at the University of Arizonas Lunar and Planetary Laboratory in Tucson. "You wouldnt see a lot of dust devil movement or drifts of dust blowing through."Instead, the megaripples in the regions that the scientists studied, near the Nili Fossae and McLaughlin Crater, migrate at almost imperceptible rates, moving only about 1 meter every nine Earth years. Nevertheless, their activity is a pleasant surprise to the planetary science community.

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Mars shifting sands revealed by long-term observations - Astronomy Magazine

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