Mars is a quiet planet, and noise propagates in the atmosphere very differently than it does on Earth: the speed of sound changes in the middle of the human-audible spectrum. These are the first results from analysis of images taken by NASA’s Perseverance rover on the Red Planet. This made it possible for the first time to analyze background noise in the range between 20 hertz and 50 kilohertz, that is, the range that people can hear, explains Baptiste Chide of the Los Alamos National Laboratory. A strange sound environment was discovered. High frequency tones would be lost after a short distance due to the CO₂ content. Therefore, a non-radio conversation in this environment would be extremely difficult even at a few meters.
Audible differences in the speed of sound.
The research team not only determined that the speed of sound on Mars, at 240 meters per second, is significantly lower than on Earth (340 meters per second), but also that there are two speeds of sound on Mars. High and low tones propagate at different speeds. Due to the immensely high CO₂ content of 96 percent and the drastically lower pressure, the sound is muffled much more than on land. This particularly affects high tones, which diffuse much more slowly than low tones. That would already have audible consequences for conversations at a distance of a few meters, explains the team led by Sylvestre Maurice of the Université Toulouse III, who led the analysis. In practice, however, future astronauts will communicate by radio anyway.
These findings were made possible by the SuperCam instrument mounted on NASA’s latest Mars rover. This not only caught the sounds of a laser that can be fired at targets on the ground up to seven meters away. With it, the rotor noises of the small Ingenuity helicopter could also be recorded. After decades of sending images from Mars to Earth, the team now explains that these are the first recordings of sounds on the red planet. Not only did this provide an understanding of how noise propagates there, but it also learned new things about the planet’s atmosphere. Aside from a few human-sent instrument noises, it’s pretty quiet there, the team adds.
Perseverance landed on Mars in February 2021. The successor to the Curiosity rover, which is still active, is intended, among other things, to be the first research device to collect soil samples on the red planet, which will then be brought back to Earth. He already has several on board. He also brought a small helicopter to Mars for the first time with Ingenuity. His presentation flights were so good that his mission was extended several times. Meanwhile, Ingenuity accompanies the rover and scans the area from above. Perseverance is currently on a forced march to an ancient riverbed that she is supposed to explore. Ingenuity takes a shortcut. The research on the sound environment on Mars has been published in the journal Nature.