The wealth of data from the encounter has excited scientists aware of the outsized influence of Martian dust on the planet’s climate. The fine-grained particles can also damage scientific instruments on Mars landers and rovers, and potentially blanket solar panels to the point of being unusable. Studying the rover’s coarse-grained records can provide insights into the way dust-running Mars missions and perhaps even future human exploration could be affected.
The sound of the dust devil, published Tuesday in an article in the journal Nature Communications, is subtle. It’s sizzling and percussive, like radio static, although more generously one could imagine a breeze ruffling some distant palm fronds.
Then comes a few seconds of silence while the dust devil’s eye glides over the rover. The sound returns for a few seconds as the dust devil’s rear wall rotates back over the rover. Then it’s all over and Mars is calm again.
This wasn’t exactly an “extreme weather” event. Mars has a negligible atmosphere, about 1 percent as dense as Earth’s, hence the storms there do not Cry. The rover sustained no damage.
Still, there is ample signal in this brief dose of noise and in the visual images captured by the SuperCam instrument atop the rover. Researchers estimate the dust devil was about 25 meters (82 ft) wide and 118 meters (387 ft) tall. That’s taller than the Statue of Liberty, including the pedestal.
“When the dust devil Perseverance passed, we could actually hear individual grain impacts on the rover,” said Naomi Murdoch, planetary scientist at ISAE-SUPAERO, an institute for aerospace engineering in Toulouse, France, and author of the new report. “We could actually count them.”
A dust devil is a bit like a miniature storm cell. It usually emerges in the middle of the day when hot air spirals up from the surface. A scientist wanting to be more technical might call this a convective vortex laden with dust. The dust is not the cause of the vortex, but only part of it.
Murdoch said the team’s success in capturing the sound of a dust devil reflects both luck and preparation. The rover’s microphone records footage lasting just under three minutes, and it does so just eight times a month. But the recordings are timed so that dust devils are most likely to occur, and the rover cameras are pointed in the direction where they are most likely to be seen.
“Then we just have to keep our fingers crossed,” she said.
It clearly worked, as Perseverance managed to capture the dust devil through multiple instruments, registering the drop in air pressure, temperature changes and the sound of impacting grains, all topped with images showing the vortex’s size and shape.
“I can’t think of any previous case where so much data from so many instruments helped characterize a single dust devil,” John Edward Moores, a planetary scientist at York University, said in an email after discovering the new one checked paper. He said the team is happy that all of the observations overlap.
“Had the [camera] Pointing in a different direction or setting the microphone observation just a few seconds later would miss key elements of the story. Sometimes it helps to be lucky in science!”
Mars rover unearths fascinating clues in search of life beyond Earth
As the Perseverance team cheers on their windy encounter, calm weather has set in Problem for another NASA robotic vehicle on Mars. The InSight lander, which landed more than 2,000 miles away in November 2018, has instruments to study the seismicity and interior of the planet.
InSight lasted a few years past its primary mission timeline, but is now in the final weeks of its scientific life with its solar panels 90 percent covered in dust. What it takes is a direct hit from a dust devil, because such vortices are capable of cleaning solar panels.
“A dust devil is like a little vacuum cleaner sweeping the surface,” said Bruce Banerdt, a planetary geophysicist at NASA Jet Propulsion Laboratory and principal investigator for InSight.
But InSight has not received a visit from a devil capable of cleaning its arrays. Banerdt said there is currently enough energy to run a seismometer for eight hours, but then it has to rest for three days while the batteries recharge.
“We’re still limping at this point,” he said.
Murdoch said this scattershot pattern of dust devils appearing on Mars remains mysterious. Planetary scientists also cannot predict when the Red Planet will have a global dust storm, she said, citing “our poor understanding of how and when dust is lifted from the Martian surface.”
But that’s changing, she hopes, because the microphone her team developed continues to listen to the sounds of this distant desert planet.