Researchers have discovered details about how sound behaves at different times and places Mars — and the results are very different from what we’re used to on Earth.
NASA Endurance rover on Mars it carries several microphones. Designed to study the properties of materials on the Red Planet, these devices picked up all kinds of other sounds, including the eerie sputtering of Mars. dust devils.
The recordings have already shown it the sound behaves strangely on Mars. For example, sounds below 240 hertz—roughly the middle C of a piano—move about 30 feet per second (10 meters per second) slower than higher-pitched sounds. That’s because carbon dioxide molecules, which absorb some of the sound energy at low frequencies, make up 95% of Mars’ atmosphere. Such bizarre features, if left unexplained, could compromise the communications of future Mars missions, especially manned ones.
With that in mind, a team of scientists from French and American institutions set out to study the speed of sound and its attenuation — its tendency to die off with distance — in the first 60 feet (20 m) of the Martian atmosphere.
First, the team collected values ​​of various parameters – including atmospheric pressure, temperature and chemical composition – at various locations on the Red Planet from Mars Climate Database. Changes in these parameters can stretch or shorten sound waves, so these factors are essential for predicting sound properties.
Related: Fly through the ‘Labyrinth of the Night’ – a Martian canyon the size of Italy – in exciting new satellite video
The team calculated the speed and attenuation of sound at different points in time in the planet’s year (which is about 687 Earth days) and at different locations in the Martian landscape, including mountain peaks and valleys. This approach was necessary because the underlying factors vary significantly over space and time. For example, in the polar regions, midday temperatures can vary by 108 degrees Fahrenheit (60 degrees Celsius) and carbon dioxide levels by 30% over the seasons.
The calculations yielded several interesting findings, which were published on May 7 in JGR: Planets. First, dust doesn’t seem to affect sound propagation, the authors said in a joint email to Live Science — much like on Earth, where a dust storm between you and an airport, for example, wouldn’t interfere with your ability to hear. aircraft taking off. The change in the speed of sound with temperature (about 0.5 m/s for each degree Celsius) is also similar to that on Earth.
However, unlike on Earth, the speed and attenuation of sound depends greatly on carbon dioxide levels. Additionally, while the speed of sound rises sharply around 240 hertz, the extent of the shift is less pronounced at lower temperatures than at higher temperatures.
The biggest difference compared to Earth, however, stems from the enormous daily fluctuations in temperature – and to a lesser extent, the concentration of carbon dioxide. For example, in the area where the Perseverance rover currently resides, mercury levels vary by about 90 degrees Fahrenheit (50 degrees Celsius) during the day. This causes sound to travel at speeds of up to 30 m/s (30 m/s) and decay three times faster in warmer hours compared to cooler hours. Changes in temperature and carbon dioxide levels also cause sound speed and attenuation to vary over the seasons, although this effect is more pronounced in the polar regions.
The results allow scientists to “predict the speed and attenuation of sound for any location on the surface of Mars at any time of year and any time of day,” the researchers told Live Science. The model may also improve scientists’ understanding of what sound-producing objects on Mars actually sound like.
“We just hear it [a sound] after the sound propagates through the atmosphere,” the authors said. “Our model can help retrieve the properties of the original sound sources.”
In addition, the model provides a glimpse of life for future human inhabitants of Mars: blows on mountaintops may be the closest to how sound behaves on Earth. At other times, and in other places, such as the afternoons at the Perseverance place, there is a jarring effect, because high sounds at close range reach the ears more quickly than lower ones; more distant sounds normally heard on Earth will not be heard at all.