NASA has released some interesting images from the Curiosity rover showing dust devils on the surface of Mars, columns of rising air that move across the ground.
Curiosity is exploring Gale Crater, a basin 154 kilometers (96 miles) across that was created when an asteroid or comet hit the planet 3.6 billion years ago. These images help to work out how wind has shaped Gale Crater, especially the peculiar Mount Sharp that towers 5.5 kilometers (3.4 miles) above the ground.
The atmosphere of Mars is 100 times thinner than Earth’s, so its winds are much less forceful than ours. But over time, they can shape the landscape, having removed the material between Mount Sharp and the rim of the crater. This effect has been studied by Curiosity and the Mars Reconnaissance Orbiter (MRO) above the planet.
"The orbiter perspective gives us the bigger picture – on all sides of Mount Sharp and the regional context for Gale Crater. We combine that with the local detail and ground-truth we get from the rover," said Mackenzie Day of the University of Texas, Austin, lead author of a study in the journal Icarus that looked at the dominant role of wind in Gale Crater, in a statement.
Gale Crater is currently experiencing its summer season, which is its windiest time of the year. So scientists are hoping to see more of how the wind moves sand grains around on the ground, which can also explain how dunes on Mars take shape.
One set of images, for example, showed small ripples of sand moving about 2.5 centimeters (1 inch) downwind. Images taken in the afternoon of the Martian day several seconds apart also showed dust devils moving over the surface.
Sand shifting underneath Curiosity from the wind. The image is 0.9 meters (3 feet) across. NASA/JPL-Caltech/MSSS
Dust devils are formed when the ground gets hotter than the air above it, causing heated air to rise and creating rising plumes of hot air and falling plumes of cold air.
When a horizontal wind blows too, vertical columns of horizontally circling air form, which move across the surface and can pick up sand. At peak activity, you could see half a dozen dust devils in one location at certain points during the day. They can get up to 10 kilometers (6.2 miles) high and span 2 kilometers (1.2 miles).
A dust devil seen by Curiosity on February 1, 2017. NASA/JPL-Caltech/TAMU
And another on February 4, 2017. NASA/JPL-Caltech/TAMU
Curiosity is now on the lower slope of Mount Sharp, where it has begun a second campaign of looking at active sand dunes on the northwestern flank of the mountain. More research like this will help us get a greater handle on how Mars changes its appearance over time.