Imagine what Mars looks like. You probably imagined a barren landscape of scattered boulders and pebbles under a reddish-brown sky. Can you imagine what Mars sounds like?
Sounds of Mars
Thanks to recent work by an international team of scientists, we have a better idea of what the Red Planet sounds like. The Perseverance rover made recordings using two microphones: one mounted on the SuperCam camera and the other on the landing gear. The team then analyzed these recordings and published the results in the journal Nature.
The specifics of the atmosphere
One of the things that stand out about Mars is its silence. It is due to the quality of the planet’s atmosphere. To put it simply, sound is elastic waves. Unlike light, they must pass through the environment, which causes its atoms and molecules to vibrate. It keeps the wave going. The atmosphere of Mars is thin and is just over 0,5% of the pressure of the Earth’s atmosphere at sea level. It is also colder, and unlike terrestrial nitrogen, its main component is carbon dioxide. All this leads to a chain of factors:
Different sound propagation speeds
The Perseverance microphones could only hear the light Martian wind. However, when Ingenuity’s robotic drone took off, they captured the whirring of wings. Sounds were also recorded from a tool for removing gaseous dust and stone chips, which cleans the rover. Their analysis led to surprises.
At first, the team thought that the device was broken: the squeak of the instrument reached the microphone much faster than expected. However, it later turned out that unlike the Earth, where sounds travel at the same speed, on Mars the difference in speed is about 10 m/s. Moreover, high sounds reach the goal faster than low ones.
The reason is the same: carbon dioxide. These unique properties of the Red Planet’s atmosphere make it unusual for the human ear. If you listened to a concert on it, sitting in an amphitheater or on a balcony, then the music would sound wrong. The high tones of the flute and harp would reach your ears earlier than the notes of the tuba and cello, but would be very quiet.