These are Star Dunes on Mars, Formed When the Wind Comes From Many Different Directions

Missions to Mars are expensive, even orbiters. They’re there to do science, not take pretty pictures. But sometimes Mars’ beauty is captured inadvertently, usually with some science mixed in.

That’s the case with this picture of star dunes captured by the HiRISE camera on NASA’s Mars Reconnaissance Orbiter.

In most regions on Mars, winds blow in a prevailing direction. It’s the same here on Earth. So most dunes appear as waves, oriented perpendicularly to the wind direction. One common type of dune is Barchan dunes and they have two “horns” that face downwind.

Barchan Dunes are formed in prevailing winds. Image Credit: unknown. CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=571880

But star dunes are different. They form in winds that shift direction. They’re comparatively rare—on Earth, only about 8.5% of dunes are star dunes.

NASA’s Mars Reconnaissance Orbiter (MRO) has an almost-famous instrument called HiRISE – High-Resolution Imaging Science Experiment. Universe Today is full of HiRISE images. HiRISE wasn’t looking for star dunes when it captured this image in 2010. It was examining a crater in Mars’ Tyrrhena Terra region, looking at the geologic aspects of possible clays detected with the MRO’s CRISM instrument.

The happy accident shows how much geologic diversity Mars has on display.

Mars’s geologic diversity is stunning. The HiRISE camera does a great job of capturing that diversity, like in this image of star dunes in a crater in the Tyrrhena Terra. Image Credit: NASA/JPL/ UArizona

Star dunes are more common on Mars than they are on Earth because of all the impact craters. The wind swirls around crater rims and comes from many directions before it reaches the sand inside the dune. All that activity shapes the sand into a beautiful pattern.

The Victoria Crater might be Mars’ most famous crater, thanks to this gorgeous image. It shows how star dunes tend to form in craters because of the shifting winds. Image Credit: NASA/HiRISE/UofA

The image of star dunes in the crater in the Tyrrhena Terra is just a small part of the entire HiRISE image. You can see the whole image here. Check it out.