For the first time, researchers have recorded the sounds of a tornado on Mars. From this they derive properties of the dust devils. They’re extremely beneficial for Mars missions for a reason.
It is just a dull rumble that lasts for several seconds – but for planetary researchers these noises are of considerable importance: Using the microphone on board the Mars rover “Perseverance”, an international team of scientists has succeeded for the first time in recording the sound of a so-called dust devil to record another planet.
It is a tornado filled with dust. From the noises picked up and other measurement data from the rover, the height of the dust devil could be determined at 118 meters and its diameter at 25 meters, the team reports in the journal “Nature Communications”.
“Dust devils are common on the surface of Mars, particularly in the Jezero crater, where the Perseverance rover landed,” explain Naomi Murdoch of the University of Toulouse in France and her colleagues. The US space agency Nasa’s vehicle landed in the Jezero crater on February 18, 2021. Since then, the researchers have observed almost 100 dust devils there. “These whirlwinds are a consequence of atmospheric turbulence and are an important mechanism for stirring up and redistributing dust on the surface,” the researchers say.
For the first time, “Perseverance” has a microphone on board, integrated into a camera. However, the microphone does not record the ambient noise continuously, but only for three minutes a day. On September 27, 2021, the researchers were doubly lucky: A dust devil walked directly over the rover – and the microphone was switched on at that time. In this way, the team was able to combine the sound of the dust devil with camera images and other measurement data, especially air pressure.
“First there was a decrease in air pressure, then the noises of the dust devil rang out,” reports team leader Roger Wiens from Purdue University in the USA. “Then there was a brief moment of silence – we were in the eye of the small hurricane. We could then hear the wind again and then the air pressure rose again.” The data shows a wind speed of 40 kilometers per hour. This is about the same speed as comparable atmospheric phenomena on Earth.
However, the air pressure on the Red Planet is only about one percent of that on Earth, so the wind is correspondingly less powerful. “So it’s not a strong wind, but it’s obviously enough to stir up dust and carry it away,” says Wiens. Due to the low air pressure, such winds do not pose any danger to Mars probes or future astronauts. On the contrary, dust devils are even advantageous: They blow off the dust that has accumulated over time from solar cells and thus extend the life of Mars probes, for example.
The teams on the Opportunity and Spirit rover were able to observe a slow deterioration in the energy supply – and then a sudden improvement again. “Then a dust devil cleaned the solar cells,” explains Wiens. In the case of the Mars probe “InSight”, however, no such effect can be observed – there are hardly any dust devils at the landing site of the probe in the Elysium plain. The researchers are now hoping for further acoustic recordings of dust devils in order to gain further insights into the atmosphere and the dust.
