On September 27, 2021, a dust devil swept the Perseverance rover off to Mars. The rover, the first instrument of its sort to record sounds on Mars, not only caught the dust devil on its cameras and weather sensors but also picked up the fragile, eerie sounds on its microphone.
According to Naomi Murdoch of the University of Toulouse, lead author of a Nature Communications report about the findings, “We were certain that the microphone was going to provide us a whole load of new observations of atmospheric phenomena on Mars that we hadn’t been able to detect previously.” And we haven’t been let down!
Thanks to the decades-long examination of Mars by rovers fitted with cameras, spectrographs, and weather sensors, we now have a better grasp of the environment on the Red Planet than ever before.
The list is currently being expanded to add sounds. The combination of data is helping scientists understand these dusty phenomena and their possible impact on future robotic and crewed missions.
Dust devils are created by the atmospheric conditions that are typical of Mars. Murdoch argued that there must be a big temperature differential between the earth and the air.
“So the air starts to ascend because the ground becomes really heated. And when the air begins to ascend, objects begin to rotate, which is how you get the whirlwind-like action.
Although this process also takes place on Earth, what distinguishes Martian dust devils is their scale. A dust devil that was recently spotted by the Perseverance spacecraft was 25 meters wide and 118 meters tall (82 feet by 387 feet), which puts it squarely within the usual range for Martian dust storms. However, because of the potential for extremely large global dust storms on Mars, they are also capable of considerably expanding.
According to Murdoch, one of the primary problems we now have is our inability to anticipate dust storms with any degree of accuracy. And it has effects on everything, including efforts to keep dust off essential solar panels so that robotic missions can continue and attempts to safely land spacecraft on Mars.
There are several unsolved concerns surrounding how dust is precisely lifted from the surface by forces like wind shear and dust devils. The fact that dust devils are very infrequent in the Elysium Planitia region, but are prevalent in the Jezero Crater, where Perseverance is located, is a particularly puzzling observation.
Due to the numerous scientific instruments on Perseverance that need time to operate, the microphone recording windows are just a few minutes long. In order to enhance their chances of seeing a dust devil during these brief intervals, the microphone team scheduled those windows at times in the afternoon when they are most active. It required meticulous preparation and a lot of luck to catch this most recent dust devil because each window was only a few minutes long and there were only eight every month.
The microphone captured the sound of little impacts, such as a single dust particle pinging on the area next to the microphone, as well as information on the wind conditions. The thickness of these particles inside the dust devil has not been detected by any other machinery. The removal of particles from the surface by dust devils might be predicted using this knowledge.
This project is only one in a growing corpus of research that employs audio data for planetary exploration.