Data from NASA's Perseverance Rover has given scientists their first clear picture of how sound travels on Mars' surface.
The Red Planet's thin, cold atmosphere, made of mostly carbon dioxide, causes sound to move slower and carry for shorter distances compared to those on Earth. An international team of scientists led by Sylvestre Maurice, an astrophysicist at the University of Toulouse in France, published the findings Friday in the journal Nature.
The team studied recordings from the surface of Mars made by two microphones on board Perseverance — one mounted on the rover's mast and another attached to the chassis.
"It's a new sense of investigation we've never used before on Mars," Maurice said. "I expect many discoveries to come, using the atmosphere as a source of sound and the medium of propagation."
Other than the pings, whirs, whines and other mechanical noises associated with the rover and its helicopter, Ingenuity, the microphones have largely picked up silence from Mars.
"At some point, we thought the microphone was broken, it was so quiet," Maurice said.
This is because the low atmospheric pressure on Mars influences the speed and distance of sound on the planet. Sound travels between 537 mph and 559 mph on Mars depending on the pitch, while sounds typically travel at 767 mph on Earth. Meanwhile, sounds begin to drop after traveling about 26 feet on Mars, compared to 213 feet on Earth.
Baptiste Chide of the Los Alamos National Laboratory in New Mexico said these data points will change throughout the year because Mars' atmospheric pressure changes with the season.
"We are entering a high-pressure season," he said. "Maybe the acoustic environment on Mars will be less quiet than it was when we landed."
Being able to listen to Mars right now has some practical effects. Researchers are able to monitor the health and operation of Perseverance and Ingenuity by listening to them operate — akin to noticing car troubles by ear.
