The Martian soundscape can be as unsettling as one might expect to hear on another world. The boom of occasional meteor impacts, the groan of the shaking ground, the whisper of an endless wind.
Now we have a front-row seat to the approach and retreat of a roaring devil as it sweeps across the surface, helping to drive the cycle of dust through the atmosphere and around the little rust-stained world.
Perseverance was the first rover to reach the surface of Mars with a working microphone attached, and the instrument has been put to good use since the rover landed in February 2021. The microphone is part of a suite of recording tools on the rover known as the SuperCam.
It is thanks to this innovative technology that we can hear for the first time what a miniature dust whirlwind sounds like on another planet. It’s funny and short and pretty awesome at the same time.
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“We can learn a lot more using sound than we can with some of the other tools,” says planetary scientist Roger Wiens of Purdue University in Indiana.
“They do readings at regular intervals.”
“The microphone allows us to sample, not at the speed of sound, but almost 100,000 times per second. It helps us get a stronger idea of what Mars is like.”
Perseverance’s microphone actually only records for three minutes a day—this is the first time it’s been triggered when a dust devil has passed, although other instruments have recorded evidence of nearly 100 other eddies where the rover is based at Jezero crater.
The dust devil flew past the rover on September 27, 2021, the 215th Martian day (or sun) of its mission. Scientists estimate that the size of the dust devil was about 25 meters (just over 80 feet) wide, while it would have been at least 118 meters (387 feet) tall.
Combining photographs with readings of wind, pressure, temperature and dust, Perseverance was also able to track the speed of the Martian mini-tornado in its path, which reached 19 kilometers (12 miles) per hour.
Rover Navcam observations of the dust devil encounter. (Murdoch et al., Nature Communications, 2022)
“This chance encounter with the dust devil demonstrates the potential of acoustic data to resolve the fast wind structure of the Martian atmosphere,” Wiens and colleagues write in their paper.
The surrounding winds would have been faster, and in the recording you can hear the silence that reflects the quiet eye of this particular small storm. Part of what makes the new information valuable is how it compares to events like this on Earth.
“The wind is fast — about 25 miles per hour, but about what you’d see in a dust devil on Earth,” says Wiens. “The difference is that the air pressure on Mars is much lower than the winds, although they are just as fast, they push with about 1% of the pressure the same speed as the wind would have on Earth.”
“Not a powerful wind, but clearly enough to throw sand particles into the air to make a dust devil.”
All the data we are currently collecting on Mars is useful for several reasons. On the one hand, it gives us a better idea of how the planet evolved, which in turn gives scientists clues about how other planets in the Universe might also be evolving.
These other planets include Earth, and since Mars is our closest planetary neighbor, our histories are closely intertwined. Comparing Earth and Mars gives us a better idea of the past and future of both planets.
There is also humanity’s ambition to one day set foot on Mars. Recordings like this hint at the kind of conditions we can expect and how those conditions could be protected or used, such as how wind could naturally clean solar panels.
“Just like Earth, there’s a different climate in different areas of Mars,” says Wiens. “Using all our instruments and tools, especially the microphone, helps us get a concrete idea of what it would be like to be on Mars.”
The research has been published in Nature Communications.