Scientists have confirmed the speed of sound on Mars, using equipment on the Perseverance rover to study the red planet's atmosphere, which is very different to Earth's.
There could be strange consequences for communication between future Martians.
The findings suggest that talking in the atmosphere of Mars might produce a weird effect, since higher-pitched sound seems to travel faster than bass notes. It is fun to think about, since Mars is unbreathable.
At the 53rd lunar and planetary science conference, planetary scientist Baptiste Chide of the Los Alamos National Laboratory announced findings that show high temperature fluctuations at the surface of Mars that warrant further investigation.
The speed of sound is not a constant. The denser the medium, the faster it goes.
Sound travels about 343 meters (1,125 feet) per second in our atmosphere at 20 degrees Celsius, but also at 1,480 meters per second in water and at 5,100 meters per second in steel.
The atmosphere on Mars is less stable than that on Earth, around 0.020 kg/m 3. That alone means that sound would be different on the red planet.
The warming of the surface during the day creates turbulence in the Planetary Boundary Layer.
Conventional instruments for testing surface thermal gradients are very accurate, but can suffer interference effects. Perseverance has microphones that allow us to hear the sounds of Mars, and a laser that can cause a perfectly timed noise.
The SuperCam microphone was used to record acoustic pressure fluctuations from the rover&s laser-induced breakdown spectroscopy instrument.
The Perseverance rover is on Mars. NASA/JPL-Caltech/MSSS
This came with an excellent benefit. Chide and his team measured the time between the laser firing and the sound reaching the microphone at 2.1 meters altitude to see how fast the sound is reaching the microphone.
The researchers wrote in their conference paper that the speed of sound retrieved by this technique is computed over the entire acoustic propagation path, which goes from the ground to the height of the microphone.
It is convoluted by the variations of temperature and wind speed along this path.
The results back up predictions made using what we know of the atmosphere of the planet Mars.
The quirk of Mars is something completely out of the ordinary, with the conditions on Mars leading to a quirk not seen anywhere else.
Due to the unique properties of the carbon dioxide molecule at low pressure, Mars is the only planet in the Solar System that has a change in speed of sound in the middle of the audible bandwidth.
The carbon dioxide molecule's collision-activated modes do not have enough time to relax or return to their original state. The sound travels more than 10 meters per second faster at higher frequencies than it does at low ones.
This could lead to a unique listening experience on Mars, with higher-pitched sounds arriving sooner to the listener than lower ones.
It's unlikely that this will pose an immediate problem, but it could be a fun idea for science-fiction writers to tinker with.
The team was able to use the microphone to measure large and rapid temperature changes on the Martian surface because of the speed of sound changes due to temperature fluctuations. Some of the blanks on Mars can be filled with this data.
The team plans to continue using SuperCam microphone data to observe how sound on Mars might be affected by daily and seasonal variations. They plan to compare acoustic temperature readings to readings from other instruments to figure out the large fluctuations.
The conference paper can be found on the website.
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