“There are only a few natural sources of sound, with the exception of the wind,” the scientists explained on the occasion of the publication of their study in the journal “Nature” on Friday. However, the five-hour audio recordings held a surprise: there are two different speeds of sound on Mars.
The recordings come from two microphones of the Mars rover “Perseverance” of the US space agency Nasa, which landed on Mars in February last year. Now they have been evaluated for the first time by a research team led by main author Sylvestre Maurice.
There was such a silence on the recordings that the scientists began to fear that something was wrong with the measurements. But then something could be heard, for example the whirring of the rotor blades of the ultra-light mini helicopter “Ingenuity” of the NASA rover.
Two speeds of sound on Mars
With their study, the scientists were able to prove for the first time that the speed of sound on Mars is 240 meters per second, slower than on Earth, where sound propagates at 340 meters per second. This was expected because the Martian atmosphere is 95 percent carbon dioxide and about 100 times thinner than Earth’s.
What surprised everyone, however, was that the sound generated by the laser traveled 250 meters per second – faster than expected. “I panicked a bit,” reported lead author Maurice. “I said to myself that one of the two measurements must be wrong because there is only one speed of sound on earth.”
So there are two speeds of sound on Mars: one for high-pitched sounds like those of the laser and another for lower frequencies like the whirring of the helicopter rotors. “All these factors would make it difficult for two people who are only five meters apart to have a conversation,” said the French research institute CNRS.