We have heard a dust devil on Mars for the first time. The Perseverance rover has the first microphone ever sent to another planetThose were detected due to the localised drop in atmospheric pressure that each dust devil causes, but their sound wasn’t recorded because the microphone is only turned on for a few seconds about twice a week. In one of those recordings, on 27 September 2021, it caught its first dust devil flinging grains of dust at the rover.
“If you were standing there, you might be able to see the dust coming towards you, but you probably wouldn’t feel very much or hear anything because of the thin atmosphere,” says Naomi Murdoch at the University of Toulouse in France. “Sound doesn’t travel very well on Mars, which is how we know these grains were hitting very close to the microphone.”
By combining the audio recording with data from Perseverance’s other sensors, Murdoch and her team calculated that the dust devil measured about 25 metres across, with a height of at least 118 metres., and it recorded a vortex passing right over the rover, which may help us predict dust storms in the future.
Dust devils are whirlwinds that loft the Martian soil into the air for a few minutes at a time before dissipating. There are millions of them skittering across the surface every day, and they have been detected by several landers – Perseverance itself has crossed paths with hundreds.
They measured an average of 60 dust grain impacts per second, similar to what other teams have measured in dust devils on Earth. Strangely, though, those impacts came in three short bursts. We would expect the dust to be mostly in the walls of the vortex, which would result in two bursts of impacts as the dust devil passed by. Images of the dust devil revealed an unexpected dust cloud in the centre of the vortex, but researchers still aren’t sure what caused it.
“To date, one of the major problems that scientists have with modelling the Martian climate is trying to predict things like when global dust storms are going to occur,” says Murdoch. “One of the reasons why we can’t model this correctly is because we don’t fully understand when, why and how dust is lifted into the atmosphere.” Dust devils loft dust into the atmosphere on a smaller scale, so studying them could help us understand and even predict bigger storms on Mars.
