Planet of Silence: The first audio recordings from Mars evaluated

“There are only a few natural sources of sound, except for the wind,” the scientists explained when their study was published in the journal Nature on Friday. However, the five-hour audio recordings came as a surprise: There are two different speeds of sound on Mars.

The recordings come from two microphones aboard NASA’s “Perseverance” Mars rover, which landed on Mars in February last year. Now they have been evaluated for the first time by a research team led by lead author Sylvester Morris.

There was such a silence on the recordings that scientists began to fear something was wrong with the measurements. But then something can be heard, for example the hum of the rotor blades of the ultra-lightweight helicopter “Ingenuity” of the NASA rover.

Through their studies, scientists were able for the first time to prove that the speed of sound on Mars is 240 meters per second, that is, slower than the speed of sound on Earth, where sound travels at a speed of 340 meters per second. This was expected because Mars’ atmosphere is 95% carbon dioxide and about 100 times thinner than Earth’s.

But what surprised everyone was that the sound produced by the laser traveled at 250 meters per second – faster than expected. “I panicked a little,” lead author Morris said. “I told myself that one of the two scales must be wrong because there is only one speed of sound on Earth.”

There are two speeds of sound on Mars: one for high-pitched sounds, such as lasers, and one for low frequencies, such as the hum of a helicopter. “All these factors will make it difficult for two people who are only five meters apart to hold a conversation,” said the French research institute CNRS.

(sda)