First audio recorded on Mars reveals two speeds of sound: NASA' Perseverance landed on Mars and its two microphones started recording, allowing scientists to hear what it is like on the Red Planet

The first audio recordings on 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 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.But the scientists were surprised when the sound made by the laser took 250 metres a second -- 10 metres faster than expected.

"I panicked a little," Maurice said. "I told myself that one of the two measurements was wrong because on Earth you only have one speed of sound."

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.It was otherwise so quiet on Mars that the scientists repeatedly feared something was wrong, the CNRS said, possibly provoking memories of two failed previous attempts in 1999 and 2008 to record sound there.

"There are few natural sound sources with the exception of the wind," the scientists said in a statement linked to the study.

The microphones did pick up numerous "screech" and "clank" sounds as the rover's metal wheels interacted with rocks, the study said.

And Perseverance is far from done eavesdropping. While its core mission lasts just over two years, it could remain operational well beyond that -- the Curiosity rover is still kicking nine years into a planned two-year stint.