As humanity edges closer to stepping foot on Mars – at least, according to NASA and the private space sector – the multiple questions surrounding life on the Red Planet seem ever more relevant.
Can we grow food on Mars? Can we produce oxygen to breathe on Mars? Is there water on Mars? Could we survive on Mars?
But what about sound on Mars? What does Mars sound like, and how does sound on Mars differ from sound on Earth?
Luckily, NASA's Perseverance rover, which has been studying Mars since 2021, has provided scientists with an idea of what Mars really sounds like.
Mars, sound and science
There are elements of how sound would 'behave' on Mars that can be gleaned solely from what we know about the Red Planet, its temperature and atmosphere.
Sound is how our ears – and our brain – interpret vibrations in the air caused by, for example, someone speaking, a dog barking or a tree falling in a forest.
So it makes sense that sound might behave differently on a different planet.
NASA says sound on Mars would take longer to get to your ear than it does on Earth.
This is because Mars is very cold. On average, it's about –63°C (–81°F) in fact. Sound on Mars travels at about 540mph, compared to 760mph on Earth.
NASA also says sound would be quieter on Mars. That's because the Red Planet's atmosphere is about 100 times less dense than Earth.
Just like temperature, this changes how sound waves behave as they travel from source to ear drum.
And on Mars only lower-pitched sounds could be heard at a distance.
The reason, according to NASA, is because Mars's atmosphere is 96% carbon dioxide, which absorbs more higher-pitched sounds.
That's the science behind sound on Mars, but what about listening to a real recording of sound on the surface of the planet?
That's where NASA's Perseverance rover comes in.
Perseverance's recording of sound on Mars
The Perseverance rover is equipped with two microphones that have captured the sound of Mars for scientists back on Earth to hear and analyse.
It's recorded Martian wind, as well as the rover's own noises – including its laser zapping a rock – and those of Ingenuity, the Mars helicopter.
You can hear these sounds and more in the two NASA videos below.
"It’s a new sense of investigation we’ve never used before on Mars," says Sylvestre Maurice, an astrophysicist at the University of Toulouse in France and lead author of a study using Perseverance's recordings of sound on Mars.
"I expect many discoveries to come, using the atmosphere as a source of sound and the medium of propagation."
Sound on Mars was recorded using the microphone on Perseverance’s SuperCam, and a second microphone on the rover's chassis.
Scientists say sound on Mars wouldn't be very different to sound on Earth, but would be quieter, more muffled and take longer to reach you.
Perseverance's recordings enable scientists to confirm what they had inferred about sound on Mars, but also to make new discoveries about Mars's atmosphere.
For example, recordings from the SuperCam microphone reveal pressure variations caused by turbulence in the Martian atmosphere.
And Martian wind gusts at short timescales were measured for the first time.
It also gave scientists an idea of how quiet it is on Mars. “At some point, we thought the microphone was broken, it was so quiet,” says Maurice.
"Mars is very quiet because of low atmospheric pressure," says Baptiste Chide of Los Alamos National Laboratory in New Mexico, a co-author of the study.
"But the pressure changes with the seasons on Mars."
That means Mars might be noisier at some times of year than at other times.
Sounds of Ingenuity and Perseverance
One of the most exciting sounds captured by the Perseverance rover on Mars is the whirring of the Ingenuity helicopter's rotors.
Ingenuity was deployed on the Red Planet on 4 April 2021 and on 19 April became the first aircraft in history to make a flight on another planet.
Its mission ended on 25 January 2024, but Perseverance was able to capture the sound of its mechanics before it flew for the final time.
Maurice says the rotors made a "distinctive, low-pitched sound at 84 hertz".
And Perseverance also captured the sound of its own lasers, which are designed to zap rocks on planet to analyse their composition.
