It’s Sol 4332 on the surface of Mars and NASA’s Opportunity rover captured something it doesn’t see every day. A dust devil.

Opportunity dust devil

Did you know: A day on Mars (Sol) is slightly longer than a day on Earth. It takes the red planet 24 hours, 36 minutes to complete a revolution on its axis (a day). A year is much longer. It takes Mars 687 Earth days to complete an orbit around the sun.

This isn’t the first time a dust devil has been seen from the surface of Mars. NASA’s rover Spirit captured a series of images back in 2005 showing a dust devil in action.

spirit dust devil

This dust devil is about 112 feet in diameter and covers nearly one mile in the animation above.

How they form

Dust devils on Mars aren’t all that different from Earth.

The key ingredients are a warm surface and cool air above. As the warm, less-dense air rises – it pushes through the cooler, denser air above it. This interaction causes the air to start circulating vertically. Add a gust of horizontal wind and “it turns the convection cells on their sides, so they begin spinning horizontally, forming vertical columns – and starting a dust devil,” says Mark Lemmon, an associate professor in Atmospheric Sciences at Texas A&M University.

While the two dust devils seen above appear to be small, not all of them stay that way. Some of the largest dust devils seen from orbit are 1 to 2 kilometers across at their base with towers of dust reaching 8 to 10 kilometers high

Here’s another image that shows how dust devils tend to form repeatedly over the same area.

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dust devil tracks on Mars

You can see how the tracks reveal the darker surface beneath the dust. It’s also why dust devils keep forming in these areas. The darker areas heat up more than the surrounding areas.

Here are a couple more images of dust devils/tracks.

dust devil mars

Mars dust devil tracks

Opportunity tries to summit hill

Last month, Opportunity took a crack at the crest of ‘Knudsen Ridge.’ It gave a good effort, but the rover couldn’t tackle the steepest slope ever attempted. At its steepest, the rover hit 32 degrees. Check out this image showing how dust and sand slid down the rover’s rear solar panel when it was climbing the hill.

dust slides off opportunity rover

Opportunity team members decided to skip the target and move on. Right now, the rover sits in an area where clay materials (forms in the presence of water) have been identified by NASA’s Mars Reconnaissance Orbiter.

You can follow Opportunity during its trek on Mars via NASA’s detailed traverse maps. Click the large versions of the images and zoom in to see where Opportunity has been.

Image credits: NASA

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