The mobile robot “Perseverance” of NASA revealed the secrets of the amazing sound scene of Mars, and it was recorded from the rover that the red planet is calm, in which sound travels slowly and at two different speeds.
And as soon as the US space agency’s robot landed on Mars a little more than a year ago, it sent the first audio recording by a microphone on Mars in the history of space exploration, at frequencies that the human ear could hear, achieving what previous missions were unable to do.
Behind the vehicle’s roar, a gust of wind could clearly be heard in this recording. Thus, after the exploration vehicles for 50 years have sent thousands of images to Earth, the red planet emerged from “acoustic nothingness”, as noted by the National Center for Scientific Research in France, commenting on the publication of a study in this regard in the scientific journal “Nature” on Friday.
This first audio recording showed the presence of previously unknown turbulence systems on Mars, according to study lead author Sylvester Morris, co-scientific director of the robot’s “SuperCam” instrument, which has a microphone designed by Isae-Supaero in Toulouse, France.
But this recording was not enough to form a clear picture. Since Mars is very quiet most of the time, two “active” sources had to be used to capture the assets provided by the robot before sending it to Mars, explained Morris, an astrophysicist from the Institute for Research in Astrophysics and Planets at the University of Toulouse.
His team benefited from the miniature helicopter “Ingenuity” accompanying the robot, and from the laser shots directed at the Martian rocks to examine their chemical composition through the sound of it colliding with them.
The researcher pointed out that these shots provided “a very localized sound source, at a distance of between two and five meters from its target, and the exact timing of its firing was known.”
It was possible to measure the speed of sound in the field, 240 meters per second, while it is 340 meters per second on planet Earth. Not surprisingly, the speed of sound is slower, given the composition of Mars’ atmosphere (96 percent of it is carbon dioxide, compared to 0.004 percent on Earth) and its very low pressure (170 times that of Earth).
However, the surprise came from the sound of the laser, which reached 250 meters per second. “There I panicked a little!” said Sylvester Morris. “I told myself that one measurement might not be true, as there is only one speed of sound on Earth, near the surface.”
In fact, there are two speeds of sound on Mars: one for high pitched sounds (laser) and one for low pitched sounds (helicopter). In addition, “sound attenuation is stronger on Mars than on Earth, especially high-pitched sound, which fades away very quickly, even at a short distance,” according to the researcher. This would make “a difficult conversation between two people, separated by only five meters,” according to the National Center for Scientific Research.
The researcher even compared it to a concert, and said, “On Earth, the sounds of an orchestra reach you at the same speed, low or high. Imagine what would happen on Mars, if you were a little further from the stage…it would take a long time for the sound to arrive.”
Morris believed that the “scientific bet” of equipping a space mission with a microphone was successful. Although this new tool is still in its infancy, continuing to listen to the sounds of Mars through it contributes to a better understanding of its atmosphere, which in the past was similar to the Earth’s and would have provided the appropriate conditions for the existence of forms of living organisms.
Thierry Foucher of the Paris Observatory – PSL, one of the study’s authors, expects that analysis of turbulence sounds, such as vertical winds called “convective plumes”, will allow “the refinement of digital models used for Martian climate and weather forecasts.”
It may be conducted by the same type of instruments audio studies of the atmosphere of the planets Venus and Titan, one of the moons of Saturn.