Space: on Mars, sound has two speeds and it attenuates faster than on Earth



It may be calm and silent, but Earthlings have managed to make the planet Mars speak. In a study published in the journal Nature (in English), Friday, April 1, researchers detail what the recordings captured by the Perseverance rover have shown.

Barely landed, in February 2021, the NASA robot sent us the first audio ever captured on Mars thanks to a microphone, at frequencies audible to the human ear, which previous missions had attempted without success. Analysis of these recordings revealed the fact that “the speed of sound is lower on Mars than on Earth: 240 m/s, against 340 m/s on our planet, summarizes the CNRS in a press release. There is nothing abnormal in it being slower, given the composition of the Martian atmosphere (which is made up of 96% carbon dioxide, whereas this share is only 0.004% on Earth) and its very low pressure (170 times more than on Earth). But the most surprising thing is that there are actually two speeds of sound on Mars, one for highs and one for lows.”notes the CNRS.

“On Earth, the sounds of the orchestra reach you at the same speed, whether they are low or high. Let’s imagine on Mars, if you are placed a little far from the stage… you will have a hell of a time lag”illustrates Sylvestre Maurice, astrophysicist at Irap (Astrophysics and Planetology Research Institute) at the University of Toulouse.

The sound environment of Mars presents other peculiarities. “The attenuation of sound is stronger on Mars than on Earth, particularly the treble which is lost very quickly, even at a short distance”, also writes the CNRS. That would make “a difficult conversation between two people separated by only five meters”.

the “scientific bet”, that of having equipped a space mission with a microphone, is successful in the eyes of the man who is co-responsible scientist for the rover’s SuperCam instrument, where the microphone designed by Isae-Supaéro in Toulouse is installed. Even if this new tool is only in its infancy, continuing to listen to Mars should help to better understand its atmosphere, which in the past resembled that of Earth and could have favored the appearance of life. Other atmospheres, such as that of Venus or of Titan, a moon of Saturn, could be the subject of sound investigations with this same type of instrument.



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