PARIS: The first audio recordings from Mars reveal a quiet planet with occasional gusts of wind where two different speeds of sound would have a strange delayed effect on hearing, scientists said on Friday.

After NASA’s Perseverance rover landed on Mars in February last year, its two microphones started recording, allowing scientists to hear what it is like on the Red Planet for the first time.

In a study published in the Nature journal on Friday, the scientists gave their first analysis of the five hours of sound picked up by Perseverance’s microphones.

The audio revealed previously unknown turbulence on Mars, said Sylvestre Maurice, the study’s main author and scientific co-director of the shoebox-sized SuperCam mounted on the rover’s mast which has the main microphone.

The international team listened to flights by the tiny Ingenuity helicopter, a sister craft to Perseverance, and heard the rover’s laser zap rocks to study their chemical composition — which made a “clack clack” sound, Maurice said.

The study confirmed for the first time that the speed of sound is slower on Mars, travelling at 240 metres per second, compared to Earth’s 340 metres per second.

This had been expected because Mars’ atmosphere is 95 per cent carbon dioxide and is about 100 times thinner, making sound 20 decibels weaker, the study said.

But the scientists were surprised when the sound made by the laser took 250 metres a second — 10 metres faster than expected.

They had discovered there are two speeds of sound on the surface of Mars — one for high-pitched sounds like the zap of the laser, and another for lower frequencies like the whir of the helicopter rotor.

This means that human ears would hear high-pitched sounds slightly earlier.

Published in Dawn, April 2nd, 2022