When I was a boy, we lived for a time at the edge of farmland — acres and acres of lettuce and corn. My brother and I would often wander those fields, looking for entertainment. We’d scan for anything, whether it was a chance to skip stones across a pond, or climb a tree, or poke a stick at a skeletonized dead animal, or find an opportunity for a dirt clod fight, or just whatever. One of the things we would do when the season was right was dust devil chasing. The right season was late spring before the planting or the fall after the heads had been plucked and the corn reduced to stubble, after at least a week of dryth, so there was dust, and then we’d see the dust devils skirling about. What else would a couple of 12 year olds do but try to run and catch them? We rarely succeeded, and when we did it accomplished little more than tousle our hair and get grit in our eyes.
I thought of this because there was a strategy we didn’t try, which was to stop and wait for one to spawn nearby and fortuitously run over us. That’s never an option for 12 year old boys, but that’s what NASA’s Perseverance rover on Mars did. They just waited for a Martian dust devil to happen on them, and recorded it.
Murdoch said the team’s success in capturing a dust devil’s sound reflects both luck and preparation. The rover’s microphone takes recordings lasting a little under three minutes, and it does that only eight times a month. But the recordings are timed for when 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 have to just cross our fingers,” she said.
That clearly did the trick, because Perseverance managed to capture the dust devil through multiple instruments, registering the drop in air pressure, changes in temperature, the sound of grains making impact, all topped off with images that show the size and shape of the vortex.
And now we can hear it!
That’s the sound of lonely ghosts on a dead planet.