Researchers have uncovered details of how sound behaves at different times and in different places on Mars, and the results are very different from what we’re used to on Earth. NASA’s Perseverance rover on Mars carries several microphones. Designed to study the properties of materials on the Red Planet, these instruments captured all kinds of additional sounds, including the eerie sound of Martian dust devils.

Records had already shown that sound behaved strangely on Mars. For example, sounds below 240 hertz (about the middle C of a piano) travel about 30 feet per second (10 meters per second) slower than higher-pitched sounds. This is because carbon dioxide molecules, which absorb some of the sound energy at low frequencies, make up 95% of the Martian atmosphere. Such peculiar properties, if ignored, could compromise communications on future missions to Mars, especially crewed missions.

With this in mind, a team of scientists from French and American institutions set out to study the speed and attenuation of sound (its tendency to fade with distance) in the first 60 feet (20 m) of the Martian atmosphere.

To start, the team collected values ​​of various parameters, including atmospheric pressure, temperature and chemical composition, at various points on the Red Planet from the Mars climate database. Changes in these parameters can stretch or compress sound waves, making these factors important in predicting sound characteristics.

The team calculated the speed and attenuation of sound at different points in the planet’s year (about 687 Earth days) and at different points of the Martian landscape, including mountain peaks and valleys. This approach was necessary because the underlying factors vary significantly over time and space. For example, midday temperatures in polar regions can fluctuate by as much as 108 degrees Fahrenheit (60 degrees Celsius) and carbon dioxide levels can vary by 30% at different times of the year.

The calculations turned up some interesting findings, published May 7 in JGR: Planets. First, dust does not appear to affect the propagation of sound, the authors wrote in a joint email to LiveScience. This is similar to the situation on Earth, where a dust storm between you and an airport, for example, will not affect your ability. to listen. planes are taking off. The variation of the speed of sound with temperature (about 0.5 m/s per degree Celsius) is similar to that on Earth.

However, unlike on Earth, the speed and attenuation of sound largely depends on the level of carbon dioxide. Also, although the speed of sound increases sharply at about 240 hertz, the extent of the shift is less pronounced at low temperatures than at high temperatures.

However, the biggest difference from Earth comes from the large fluctuations in temperature and, to a lesser extent, carbon dioxide concentration from day to day. For example, in the area where the Perseverance rover is currently located, the mercury fluctuates by about 90 degrees Fahrenheit (50 degrees Celsius) throughout the day. This causes sound to travel at up to 100 feet per second (30 m/s) and decay three times faster during hot hours than during cold hours. Although changes in temperature and carbon dioxide levels also cause changes in the speed of sound and attenuation of sound at different times of the year, this effect is more pronounced in the polar regions.

The results allow scientists to “estimate the speed and attenuation of sound for any location on the surface of Mars at any time of year and at any time of day,” the researchers told LiveScience. The model could also improve scientists’ understanding of how sound-producing objects on Mars actually sound.

“We hear it [звук] But after the sound travels through the atmosphere,” the authors said, “our model can help restore the properties of the original sound sources.”

In addition, the model gives an insight into the life of future inhabitants of Mars: The morning on the mountain tops may be the closest to how sound behaves on Earth. At other times and places, such as afternoons at the Perseverance site, there will be a sharp effect as loud sounds at close range will reach the ear faster than quiet sounds; More distant sounds normally heard on Earth will not be heard at all.