In-depth analysis of these sounds has made the sound generated by the turbulence of the Martian atmosphere perceptible. They are due to the composition of the Martian atmosphere (96% CO 2, compared to 0.04% on Earth) and the very low atmospheric surface pressure (170 times lower than on Earth).Īfter one year of the mission, a total of five hours of recordings of the acoustic environment have been obtained. All these various factors would make it difficult for two people standing only five metres apart to have a conversation. Sound attenuation is greater on Mars than on Earth, especially for high frequencies, which, unlike low frequencies, are attenuated very quickly, even at short distances. However, the most surprising thing is that it turns out that there are actually two speeds of sound on Mars, one for high-pitched sounds and one for low frequencies 4. The researchers show that the speed of sound is lower on Mars than on Earth: 240 m/s, as compared to 340 m/s on our planet. By studying the propagation on Mars of these sounds, whose behaviour is very well well understood on Earth, they were able to accurately characterise the acoustic properties of the Martian atmosphere. In addition to this investigation, the scientists focused on the sounds generated by the rover itself 3, including the shock waves produced by the impact of the SuperCam laser on rocks, and flights by the Ingenuity helicopter. It is obvious that, apart from the wind, natural sound sources are rare. First of all, they reveal that Mars is quiet, in fact so quiet that on several occasions the scientists thought the microphone was no longer working. These sounds fall within the human audible spectrum, between 20 Hz and 20 kHz. Perseverance first recorded sounds from the Red Planet on February 19, 2021, the day after its arrival. This scientific challenge led them to design a microphone dedicated to the exploration of Mars, at ISAE-SUPAERO in Toulouse, France. The scientific team 1 for the French-US SuperCam 2 instrument installed on Perseverance was convinced that the study of the soundscape of Mars could advance our understanding of the planet. Now, NASA's Perseverance mission has put an end to this deafening silence by recording the first ever Martian sounds. For 50 years, interplanetary probes have returned thousands of striking images of the surface of Mars, but never a single sound.
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