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Scientists calculate the speed of sound on Mars, thanks to the Perseverance rover

How alien is the concept of sound on Mars? NASA's Perseverance rover is providing answers.

Scientists calculate the speed of sound on Mars, thanks to the Perseverance rover
A selfie taken by NASA's Perseverance rover. NASA/JPL-Caltech

NASA's Mars Perseverance mission has achieved another historic first: The rover that landed on Mars in February 2021 helped scientists confirm the speed of sound on the red planet.

The scientists behind the discovery used equipment aboard the rover, including a laser and the rover's SuperCam microphone, they explain in a paper presented at the 53rd Lunar and Planetary Science Conference earlier this month.

Confirming the speed of sound on Mars

The speed of sound is not a constant throughout the universe, as it travels at different speeds depending on the density and temperature through which it travels — the denser the medium, the faster sound travels.

In Earth's atmosphere, sound travels about 343 meters per second at about 20 degrees Celsius. Traveling through water, however, it travels at a speed of 1,480 meters per second.

The atmosphere on Mars is very different from the one we're used to here on Earth, which means sound also travels very differently on the red planet. Mars has much lower air pressure and less atmosphere than Earth — about 0.020 kg m3 compared to about 1.2 kg/m3 on Earth.

The scientists behind the new experiment used the Perseverance SuperCam microphone and a laser aboard the rover that can trigger a perfectly timed noise. Using the microphone, they were able to study the properties of sound around the rover's vicinity, allowing them to confirm predictions made using the information we know about Mars' atmosphere. They showed definitively that the speed of sound near the surface of Mars is approximately 240 meters per second.

High-pitched sounds win the race on Mars

As the popular misconception goes, no one can hear you scream in space. In reality, pressurized habitats, comms equipment, and spacesuits allow astronauts to speak freely. All the better, because without that equipment, our experience of communicating on Mars would be completely alien, in more ways than one.

The new findings also showed that sound has different characteristics when traveling through Mars' atmosphere. The study shows, for example, that higher-pitched sound travels faster than bass notes on Mars. 

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Though future Mars astronauts would communicate with each other in pressurized, oxygenated habitats, it's interesting to think about the wild implications of this sound perception if two humans were able to communicate out in the open on Mars. 

"Due to the unique properties of the carbon dioxide molecules at low pressure, Mars is the only terrestrial-planet atmosphere in the Solar System experiencing a change in speed of sound right in the middle of the audible bandwidth (20 Hertz to 20,000 Hertz)" the researchers wrote in their paper.

They added that this could lead to a "unique listening experience" on Mars. Hypothetically speaking, it might let people with higher-pitched voices communicate faster than those with lower voices. The team aims to continue using the Perseverance SuperCam microphone to collect data to understand better how sound travels on Mars. Their work joins a lofty list of historic firsts achieved by the Mars Perseverance mission, including the first off-world controlled flight and the first extraction of breathable oxygen on the red planet.

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