What would conservation look like between two earthlings on Mars? For something completely inaudible, if we are to believe a study published on Friday, April 1 in a very serious review nature. And for good reason, CNRS researchers revealed, thanks to an analysis of the sounds recorded by the Persévérance robot, that there are two velocities of sound (one for treble and one for bass) and much stronger sound attenuation on red. planet from the earth.

Mars’ peculiarities

In general, sound varies a lot from one environment to another: temperature, altitude, materials, all properties that have an impact on the nature of sound. In the atmosphere, at an ambient temperature of 20 degrees, sound travels through the air at a speed of 343 meters per second. But the red planet has other properties that influence the behavior of sound. Carbon dioxide molecules, which are exposed to low pressures (170 times less than those on Earth), have “unique” properties that affect sound waves even within audible frequencies. As a result, frequencies above 240 Hz travel faster on Mars than lower frequencies. Obviously, high-pitched sounds come before low-pitched sounds. “This could stimulate a unique listening experience on Mars,” note the researchers.

Perseverance robot records the first sounds from Mars: the sound of the Creativity helicopter in flight

special measures

The day after the Perseverance landing, the microphone (of a French design mounted on the robot’s SuperCam camera) recorded the first sounds of the planet. “This first capture revealed hitherto unknown perturbation systems,” says Sylvester Morris, an astrophysicist at IRAP (the French Institute for Research Astrophysics) in charge of SuperCam. But this passive listening was not enough. The astrophysicist explained, since Mars is very quiet most of the time, it was necessary to use two active sources of sound on board the Earth. And so his team used flights of a small Ingenuity helicopter, a perseverance traveling companion, and lasers shot at the rocks to examine its chemical composition (clack clack noise). “We had a very local sound source there, two and five meters from its target, and we knew from it exactly when it was launched,” the researcher explains.

The surprise came from the sound of the laser and … 250 meters per second. “There, I panicked a little! I told myself that one of those two measurements was wrong, because on Earth, near the surface, there is only one velocity of sound,” explains Sylvester Morris. However, there are two speeds: one for treble (laser), and one for bass (helicopter). Sylvester compares Morris: “If we were 8 meters away on Mars, it’s as if we were talking 65 meters away on Earth.” The discussions are likely to be really difficult.