Perseverance records the first ever sounds from Mars
NASA's Perseverance rover, which has been exploring the surface of Mars since February 2021, has recorded the acoustic environment of the Red Planet for the first time.
An international team led by an academician from the University of Toulouse III - Paul Sabatier, including scientists from CNRS and ISAE-SUPAERO, analyzed these sounds, which were obtained using the SuperCam instrument constructed in France under the direction of the French space agency CNES. Their findings were published on April 1, 2022, in the journal Nature.
In 50 years, interplanetary probes have produced thousands of remarkable images of the surface of Mars, but so far not a single sound. NASA's Perseverance mission has now ended that deafening silence by recording the first-ever sounds of Mars. The science team that installed SuperCam on Perseverance was convinced that studying the soundscape of Mars could advance our understanding of the planet.
Perseverance first recorded sounds from the Red Planet on February 19, 2021, just a day after it landed. These sounds fall within the human audible spectrum between 20 Hz and 20 kHz. First of all, they reveal that Mars is quiet, so quiet in fact that scientists have thought several times that the microphone no longer works. Other than the wind, other natural sources of sound are rather rare.
In addition to this research, the researchers also focused on sounds generated by the rover itself, including shock waves produced by the impact of the SuperCam laser on rocks and the flights of the Ingenuity helicopter. By studying the propagation of these sounds on Mars, they were able to accurately characterize the acoustic properties of the Martian atmosphere.
The researchers found that the speed of sound is lower on Mars than on Earth: 240 m/s compared to 340 m/s on our planet. Most surprising, however, is the fact that there are two sound speeds on Mars, one for high and one for low frequencies. Sound attenuation is greater on Mars than on Earth, especially for high frequencies, which, unlike low frequencies, are attenuated very quickly even over short distances. All these factors would make it difficult for two people standing only five meters apart to have a conversation. They are caused by the composition of the Martian atmosphere (96% CO2 compared to 0.04% on Earth) and the very low atmospheric surface pressure (170 times lower than on Earth).
After a year of the mission, it was possible to obtain a total of five hours of recordings of the acoustic environment of Mars. Due to the in-depth analysis of these sounds, the sound generated by the turbulence of the Martian atmosphere is perceptible. Studying this turbulence, on a scale 1,000 times smaller than anything previously known, should improve our knowledge of the interaction of the atmosphere with the Martian surface. In the future, the use of additional robots equipped with microphones could help us better understand planetary atmospheres.