on Mars have been photographed many times from above, and a picture says nothing about what is going on inside one. In September 2021 one passed directly over a rover whose microphone happened to be running. What did it pick up?
Grains hitting the rover. The microphone caught short ticks as dust struck the body, and from those you can estimate how dense the dust inside was. Alongside it the navigation camera photographed the column and pressure, wind and temperature were logged. Together they describe a vortex about 25 meters across, at least 118 meters tall, moving at some five meters a second.
A dust devil forms when hot ground warms the air above it and that air rises in a narrow, spinning column. On Mars they are common and enormous, which is why they lift dust into the whole atmosphere.
In September 2021 was running exactly as a vortex passed directly overhead. Alongside it the navigation camera was photographing, and pressure, wind and temperature were logged.
is what lets anyone rebuild the event. A drop in pressure marks the center, the wind gives the direction, and the image gives the size. Out of the combination came a vortex about twenty-five meters across, moving at some five meters a second.
What the microphone added is short ticks, made as grains struck the rover, and from those the density of the dust can be estimated. This was a chance encounter with one vortex, and the height was , by fitting a model, rather than measured directly.
wat. A microphone on Mars heard a vortex some 25 meters across, and the grains of dust that struck the rover as it passed over.
wat wat
Sound makes it possible to measure the density of grains inside a vortex, and to improve understanding of dust movement that can wear equipment down and change the atmosphere of Mars.
How do we know?
The researchers synchronized sound from the microphone with images, pressure, wind and temperature, and compared the sequence against a model of a vortex passing over the measuring point.
What is still unknown
This was a chance encounter with one vortex in Jezero crater. The structure and load of others may differ, and the height was inferred from the data rather than measured directly along its length.
Learn something?
Where to next
What did the water at Jezero crater do before it left?Mars
Are the dark streaks on Mars flowing water?Mars
They had an alligator bellow in helium. Which part of its voice changed?sound