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Polka Dots on Mars: NASA Spots Unusual Circles of Sand

Spot the spots on Mars.

Processed NASA MRO view of dark-looking sand dunes on Mars. Smaller, lighter ripples surround the dunes, some of which look like circular polka dots.
This would fit right in with '80s fashion.

This story is part of Welcome to Mars, our series exploring the red planet.

Turns out Mars may have a sense of fashion, and it's into a classic pattern: polka dots. NASA's Mars Reconnaissance Orbiter spacecraft, a longtime resident of the planet, captured a fascinating image of sand dunes with notably round shapes.  

MRO's High Resolution Imaging Experiment (HiRise) camera has snapped some delightful dunes before, including some more typical crescent-shaped dunes. "Sand dunes of many shapes and sizes are common on Mars. In this example, the dunes are almost perfectly circular, which is unusual," wrote planetary geologist Alfred McEwen for a HiRise picture-of-the-day feature Thursday.

Take a closer look at those pleasingly round Martian dunes.


Mars is a dusty, sandy, windy place, making it a perfect planet for sand dune formation. A close look shows these dunes aren't exact circles. "They are still slightly asymmetrical, with steep slip faces on the south ends. This indicates that sand generally moves to the south, but the winds may be variable," said McEwen.

The HiRise camera is operated out of the University of Arizona. MRO snapped the dunes in late November last year. Researchers were studying the area to monitor for seasonal changes in frost coverage. This image shows frost is absent from the landscape.

Mars views like this may look otherworldly, but they show a connection between our two planets. We have scenic dunes here on Earth, too, that tell similar stories about the wind and the changing of the seasons. There's plenty of beauty to be found on both planets.