Martian dunes in 3D

Scientists are tracing the movement of dust over

Martian aeons using a highdefinition camera from orbit. A Twitter account for the Mars Reconnaissance Orbiter’s High Resolution Imaging Experiment, at work at Mars since 2006, recently posted a picture of barchan dunes formed by the Red Planet’s winds pushing continuously in a single direction. “Who doesn’t like an image of dunes in 3D,” a tweet said along with the picture. “Pay attention to the sand ‘thread’ on the right side of the image. Interesting how that might have formed.”

While mission experts provided few details with the image, scientists have been probing the Nili Patera region for many years now in an attempt to figure out how the dunes evolve over time. A 2012 study showed remarkably swift movements across 105 days, during which some dunes travelled as much as 4.5 metres (15 feet). Barchan dunes are formed as the wind slowly moves sand grains up the slope of the dunes, creating small ripples on the slope. “When the sand grains arrive at the top, they fall down the steeper and shorter slope, which as a consequence has no ripples,” NASA said. “It’s this gradual sand movement that causes the dunes to slowly move over time.”