NASA’s Perseverance rover shows for the first time how fast sound travels on Mars

If that Perseverance Rover landed on Mars in February 2021, bringing with it a suite of instruments including the typical cameras and the less typical lasers. But it brought with it something else – the first microphone to work and record on the Red Planet.

New research results have now been published in nature on Friday reveals a strange quirk of Mars that has remained hidden from us all along: the red planet has not one, but two speeds of sound. The finding has major implications for all future human endeavors to Mars.

“It’s a new type of probe that we’ve never used on Mars before,” says Sylvestre Maurice, an astrophysicist at the University of Toulouse in France and lead author of the study, in a statement. Maurice is specifically referring to the Perseverance rover’s SuperCam, which has a built-in microphone.

“I expect a lot of discoveries,” he adds.

Measurement of the speed of sound on Mars

Mars long ago lost most of its atmosphere. Once upon a time, the red planet’s ancient atmosphere allowed liquid water to accumulate on the planet’s surface – potentially sustaining life on the surface. But thanks to the force of the solar winds pounding the planet, most of that protective atmosphere is now gone.

Today, Mars is surrounded by a thin carbon dioxide atmosphere that is less than 1 percent of Earth’s pressure at sea level. This (at least for us) unusual atmosphere gives the red planet its unusual acoustic properties nature paper explained.

The discovery – Because of Perseverance’s unique toolkit, NASA scientists have the opportunity for the first time to hear sounds on Mars and compare their properties. The discovery came from scientists on Earth listening to the pew-pew of Perseverance’s lasers smashing into rocks — realizing that those sounds seemed governed by different laws than the sound of the whirring rotors of Perseverance’s copter companion, Ingenuity .

Measurements by Ingenuity had already estimated the speed of sound on Mars to be 240 meters per second – about 100 meters per second slower than the speed of sound on Earth (347 meters per second). These sounds are also 20 decibels quieter than the sounds on Earth, according to the paper.

But Perseverance’s laser sounds are faster than Ingenuity’s whirr. The sound of the laser pulse travels 10 meters per second faster – 250 meters per second. The reason for this seems to lie in the acoustics of the noise: the lasers are high, but the rotor whirr is low.

“On Earth, you reach the sounds of an orchestra with the same speed, whether they are low or high,” says Maurice in an interview with Agence France-Presse.

“But imagine yourself on Mars, if you’re a little bit far from the stage, there’s going to be a big lag.”

So you would hear the oboe much earlier than the tuba, to follow the analogy. This means future Mars astronauts could experience unusual audio dissonance – they’ll hear higher-pitched sounds sooner than lower-pitched sounds, even if they’re coming from the same place.

Don’t you think so? You can listen to the sounds on Mars yourself:

Why 10 meters per second matters – While 10 meters per second may not sound like a huge difference, France’s Center National de la Recherche Scientifique, the country’s largest scientific agency, says it would actually result in two astronauts having trouble understanding each other if they would try to talk while both stood only 15 feet apart.

There are a few other unusual quirks with Mars sounds — for example, the distance that sounds actually carry. According to NASA, deep sounds on Mars begin to attenuate as little as 26 feet from their source. High tones may not get that far and remain audible.

“Mars is very calm because of the low atmospheric pressure,” Baptiste Chide said in a statement. Chide is a researcher at Los Alamos National Laboratory in New Mexico and a co-author of the study.

“But the pressure changes with the seasons on Mars,” he adds. In autumn the pressure changes and therefore the sounds on the planet can also be different.

“We’re entering a high-pressure season,” says Chide. “Perhaps the acoustic environment on Mars will be less quiet than when we landed.”

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