unknownskywalker:

MRO catches Mars sand dunes in motion

Images from NASA’s Mars Reconnaissance Orbiter show sand dunes and ripples moving across the surface of Mars at dozens of locations and shifting up to several yards. These observations reveal the planet’s sandy surface is more dynamic than previously thought.

While red dust is known to swirl all around Mars in storms and dust devils, the planet’s dark sand grains are larger and harder to move. Scientists thought the dunes and ripples on Mars either did not budge or moved too slowly for detection. Initial images from the (HiRISE) camera documented only a few cases of shifting sand dunes and ripples. Now, after years of monitoring the Martian surface, the spacecraft has documented movements of a few meters per year in dozens of locations across the planet.

The air on Mars is thin, so stronger gusts of wind are needed to push a grain of sand. Wind-tunnel experiments have shown that a patch of sand would take winds of about 80 mph (nearly 130 kilometers per hour) to move on Mars compared with only 10 mph (about 16 kilometers per hour) on Earth. Measurements from the meteorology experiments on NASA’s Viking landers in the 1970s and early 1980s, in addition to climate models, showed such winds should be rare on Mars.

Space is awesome.