What do we hear on Mars?
We now know.
The Perseverance robot had recorded in February 2021, a few hours after landing there, the sound environment of the red planet for the first time.
In a study published this Friday, in the journal Nature, researchers, led by Sylvestre Maurice, from the University of Toulouse III – Paul Sabatier, analyzed what was really heard in this “deafening silence”.
They conclude in particular that two people, a few meters apart, could not hold a conversation on Mars.
And for good reason: there are two speeds of sound, depending on whether it is high or low, and sound attenuation is much stronger on Mars than on Earth.
Meticulous work.
A first recording had already been broadcast when it was first captured.
We could hear… nothing.
The silence is sometimes such that the researchers believed several times that the microphone, placed on Perseverance, specially created for the Martian environment, was no longer working.
The challenge is daunting: to learn about Martian sounds without knowing anything about it.
To do this, the researchers applied themselves to determining the differences in the sounds produced by the impact of the SuperCam laser on the rocks and the flights of the Ingenuity helicopter, compared to those produced on Earth.
Thanks to this, we can therefore identify the differences and draw an observation of what is actually happening on Mars, where natural noises, apart from the winds, are very rare.
VIDEO.
The first Martian sound released by NASA
Two different speeds of sound.
Imagine talking to someone who may speak the same language as you, but who doesn't understand what you're saying.
This is more or less what would happen on Mars, according to this study.
The researchers were able to determine that there were two speeds of sound depending on whether the sounds were low or high: about 240 m/s for frequencies below 240 Hz, 250 m/s above.
The speed of sound on Mars is also lower on Mars (240 m/s on average) than on Earth (340 m/s).
Stronger and variable sound attenuation.
If the speed of sounds differs depending on whether they are high or low, their attenuation also changes.
Thus, on the surface of the red planet, the low sounds can last a long time when the high sounds are quickly lost.
These differences can be explained by the composition of the atmosphere of Mars – composed of 96% CO2, against 0.04% on Earth – and the very low pressure on its surface – 170 times lower than on Earth.
