NASA’s Mars InSight lander is designed primarily to study the Red Planet’s interior, but it’s already produced a big bonus in the form of the first listenable sounds of the Martian wind.
The low-frequency sounds, plus an audio version that’s been bumped up a couple of octaves to enhance listenability, were released today by the mission team at NASA’s Jet Propulsion Laboratory.
Cornell University’s Don Banfield, who leads the science team for InSight’s Auxiliary Payload Sensor Subsystem, or APSS, said the sound “reminds me of sitting outside on a windy afternoon.”
The Dec. 1 detection took advantage of several components of the car-sized lander, including its solar panels.
“You can think of it rather in the same way as the human ear,” said Imperial College London’s Tom Pike, the science lead for InSight’s Short Period Seismometer.
The solar panels are analogous to eardrums, picking up vibrations as the winds sweep past. Those vibrations are passed along by structures on the lander that would be analogous to the bones of the inner ear. And the seismometer serves as the cochlea for InSight’s ear. Readings from the seismometer are sent along as data to the lander’s electronics and transmitted back to Earth.
The air pressure sensor that’s part of the APSS instrument suite also detected the winds.
Based on the data, scientists calculate that the winds were blowing at 10 to 15 mph, from northwest to southeast. That wind pattern is consistent with the direction of dust devil tracks that were observed in the landing area from orbit, NASA said.
In a news release, InSight principal investigator Bruce Banerdt said the wind detection was an “unplanned treat.”
“But one of the things our mission is dedicated to is measuring motion on Mars, and naturally that includes motion caused by sound waves,” he said.
Because InSight’s seismometer is designed to measure seismic activity, the recorded sounds are near the lower edge of the human ear’s sensitivity, around 50 Hz. The APSS air pressure sensor recorded vibrations at an even lower frequency, around 10 Hz. Such frequencies would be heard more easily by elephants or whales, scientists said.
Even when the frequency is scaled up by two octaves, the audio sounds like the low rumble of white noise.
Winds on Mars are a lot different from winds on Earth, largely because Mars’ carbon-dioxide atmosphere is only 1 percent as dense as Earth’s. Pike said InSight detected “quite strong winds, but because of the low density they have a different effect.” Martian winds can blow with as much speed as hurricanes on Earth, in excess of 80 mph, but even then, they wouldn’t pack as much punch as the fictional winds that felled astronaut Mark Watney in “The Martian.”
There have been other detections of wind on the Martian surface — for example, by weather instruments on the Viking 1 lander in the 1970s that had relatively low sensitivity. A microphone was included among the instruments on NASA’s Mars Polar Lander, which failed during its descent to the Martian surface in 1999.
Although the rumble that InSight detected serves as the first sampling of Martian sounds, there’s lots more to come. The spacecraft’s air pressure sensor will be continuously recording atmospheric vibrations — that is, winds — for the purposes of adjusting the seismic data that the seismometer will be collecting once it’s set down on the surface. And NASA will be putting two microphones on the rover it’s planning to send to Mars in 2020.
In the months ahead, Banfield said he’s hoping InSight’s sensors will pick up the sounds of gusts or other variations in the steady breeze of a Martian afternoon.
“To me, it’s fun to imagine that I’m there,” he said. “That’s why we do this.”