Scientists say the first sound recordings on Mars reveal a quiet planet with occasional winds where two different speeds of sound will have a strange effect on hearing.
After NASA’s pre-rover landed on Mars in February of last year, our microphone began recording, allowing scientists to hear what it looked like on the Red Planet for the first time.
A study published in the journal Nature last Friday, in which scientists presented their first analysis of five hours of sound picked up by Perseverance microphones.
The sound revealed a previously unknown disturbance on the surface of Mars, said Sylvester Morris, lead author of the study and co-scientific director of the shoebox-sized SuperCam vehicle attached to the rover’s mast that contains the main microphone.
Morris told AFP that the international team listened to the flights of the Ingenity micro-helicopter, a sister vehicle for Perseverance, and heard the buzzers of the lasers in the rover to study its chemical composition, which made a “clicking sound”.
“We had a very local sound source, two and five meters (six to 16 metres) from its target, and we knew exactly when it was going to launch,” he said.
The study confirmed for the first time that the speed of sound is slower on Mars, traveling at 240 meters per second, compared to Earth’s speed of 340 meters per second.
The study said this was expected because Mars’ atmosphere contains 95 percent of carbon dioxide – compared to 0.04 percent of Earth’s – and is about 100 times thinner, making the sound 20 decibels weaker.
But the scientists were surprised when the sound from the laser took 250 meters per second – 10 meters faster than expected. “I panicked a little,” Morris said. “I told myself one of the measurements was wrong because on Earth you only have one speed of sound.”
They’ve discovered that there are two speeds of sound on Mars – one for high-pitched sounds like a laser blasting, and one for lower frequencies like the hum of a helicopter spinning. This means human ears will hear high-pitched sounds a little earlier.
“On Earth, the sounds of an orchestra reach you at the same speed, whether it’s low or loud,” Morris said.
“All these factors will make it difficult for two people to have a conversation at a distance of only five meters (16 feet),” French research institute CNRS said in a statement.
The center said it was so quiet on Mars that scientists repeatedly feared something was wrong, which could evoke memories of two previous failed attempts in 1999 and 2008 to record audio there.
“There are few natural sources of sound except for the wind,” the scientists said in a statement linked to the study. The study said the microphones picked up many of the “squeak” and “clack” sounds when the vehicle’s alloy wheels interacted with the rocks.