The Sound of Wind on Mars

   

InSight Spacecraft with solar panels that vibrate in Martian winds

In 2016 the long-sought proof of gravitational waves arrived in the form of a cosmic sound, a “chirp” signaling the merging of two black holes 1.3 billion light years away from Earth. A couple of weeks ago, we were treated to the “sound” of wind on Mars. Wind moving across the InSight spacecraft’s solar panels caused fluctuations in pressure that vibrated the panels, and the vibrations were recorded on the spacecraft’s seismometer. These vibrations occurred at a low frequency, out of the range of most human hearing; but by shifting the frequency up an octave they could easily be heard. One of the scientists of the InSight project compared the panels to a flag waving in the wind, creating pressure oscillations that the ear hears as flapping. When I listened to it, however, it sounded like Earth wind noise recorded by a microphone—which doesn’t sound like wind as normally heard, at a distance, but as if close and blowing directly into and across the ear. Making the strange thus familiar is, oddly, comforting when one thinks about what it would be like to live in the Martian environment, with its atmosphere chiefly of carbon dioxide, as if eons ago the inhabitants of Mars were overcome by a “greenhouse effect” far worse than Earth’s—although if we keep burning fossil fuels while global warming releases other CO2 into the atmosphere we may be on our way to an irreversible Martian atmosphere eons hence.