By: Lucas Ku
Having a conversation on Mars would be difficult. That’s partly because Mars can be really cold, and your teeth may be chattering. But it’s also because the Red Planet’s thin atmosphere of mostly carbon dioxide doesn’t carry sound well. In fact, someone speaking next to you on Mars would sound as quiet as if they were talking 60 meters (200 feet) away.
Baptiste Chide is a planetary scientist at Los Alamos National Laboratory in New Mexico. He and his colleagues shared these new findings about the sound on Mars in the May 26 issue of Nature. Chide’s team analyzed some of the first sound recordings ever made on the Red Planet. The recordings had been picked up by a microphone on NASA’s Perseverance rover. This space robot has been exploring Mars since February 2021. What Perseverance recorded weren’t the sounds of events on Mars. They were noises made when the rover fired a laser at small rocks nearby. That ZAP! created a sound wave — similar to THUNDER, but on a much smaller scale. Chide and his team studied about five hours’ worth of sounds collected in this way.
When a sound wave moves through air or fluid, it adds energy to the molecules around it. Air will gradually move that energy around. This is called the relaxation effect. For sound waves traveling through the air, relaxation depends on the frequency of the sound and the type of molecules in the air. On Mars, the relaxation after a high-pitched sound happens faster than after a low-pitched sound. That’s because the atmosphere has low pressure and is made mostly of carbon dioxide.
Measuring the speed of sound can give scientists a precise way to study the Martian atmosphere. Air pressure, temperature, and humidity all affect the speed of sound. So, by measuring changes in the speed of sound over time, researchers can learn more about Martian weather. With Perseverance broadcasting more sounds back to Earth, scientists will be able to study how its soundscape changes over the course of Martian seasons.