Dust Devils Detected By Seismometer Could Guide Mars Mission

The whirl of a dust devil occurs when ground heating creates a layer of hot, buoyant air that rises in plumes and begins to spin. These vortices are usually invisible, unless they pick up a cloaking layer of dust. In effect, the vortices are miniature low pressure systems, where air presses down on the ground with less weight inside the system compared to outside the system.

Lorenz and colleagues deployed eight pressure loggers in a cross formation around the seismic station. Their goal was to see if they could match up instances of sharp, temporary pressure drops–which would indicate a passing dust devil–with any distinctive seismic signatures produced at the same time.

The researchers were able to pair two dust devil pressure drops, 10 minutes apart, with seismic signatures. The seismometer proved to be sensitive enough to measure ground tilts of about 12 millionths of a degree caused by the dust devils, they found.

A dust devil measuring about 10 meters in diameter can cause a drop in pressure equivalent to removing the weight of a small car from the ground surface, Lorenz noted. “So a large dust devil can cause a very significant change in the loading of the ground, and it is no surprise the ground deforms by a tiny amount,” he said. “In essence, the dust devil sucks on the ground, pulling it upwards like a tablecloth pinched between thumb and forefinger. So the ground tilts away from the dust devil.”

Data collected by the seismometer can tell the researchers something about the direction of the dust devil’s path, and the overall tilt signal also provides a picture of how elastic the ground is when it pulls up and settles again in the wake of the vortex. Elasticity is partially determined by the composition of rocks and dust that make up the ground, making it a useful tool in exploring the nature of Mars’ near-surface layers.