Nature has published a new article about the acoustic environment of Mars, called “In situ recording of Mars soundscape”, from a long term research done by a vast group of astrophysicists and space explorers, primarily based on recordings taken by NASA’s Perseverance rover, which has been on the planet since February 2021 and has discovered that the “red planet” has two different speeds of sound, as well as some special acoustic proprieties.
The spacecraft features two microphones coupled to two cameras, which are focused on capturing the rover’s sounds on landing as well as atmospheric elements such as Martian wind. In the research, they have found several interesting information so far:
Sound travels in a slower speed than the 767 miles per hour it makes on Earth, featuring two speeds of sound. “On Mars, low-pitched sounds travel at about 537 mph (240 meters per second), while higher-pitched sounds move at 559 mph (250 meters per second).”
Since 96% of Mars atmosphere is carbon dioxide (and its density is 100 times less than Earth’s), it absorbs high-pitched sounds and only low frequencies are able to travel longer distances. “This effect is known as attenuation — a weakening of the signal at certain frequencies — and it would be more noticeable the farther you were from the source.”. That results in a quiet environment: Sound begins to drop at 26 feet from a source, so the recordings had to be done with “sensors measuring a few millimeters in diameter only.”
One of the most striking features of the sound recordings, Maurice said, is the silence that seems to prevail on Mars. “At some point, we thought the microphone was broken, it was so quiet,” […] “Mars is very quiet because of low atmospheric pressure,” said Baptiste Chide of Los Alamos National Laboratory in New Mexico, also a coauthor of the study. “But the pressure changes with the seasons on Mars.”NASA