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That was the response of Dave Gruel, lead engineer for the Perseverance rover’s entry, descent and landing (EDL) microphone, after hearing audio recordings of the machine driving across the surface of Mars.
“But,” he continued, “if you take a minute to consider what you’re hearing and where it was recorded, it makes perfect sense.”
NASA released two audio clips yesterday (17 March) from the rover’s 27.3m drive 10 days earlier. One, lasting for 16 minutes, is an unfiltered recording from the off-the-shelf EDL microphone, which was not intended for surface operations. Noise from the interaction of the wheels and suspension with the surface can be heard, as well as a high-pitched scratching noise.
The Perseverance engineering team is evaluating the source of the scratching noise, which might be electromagnetic interference from one of the rover’s electronics boxes, or interactions between the mobility system and the Martian surface.
The other ‘bangs, pings and rattles’ come down to the nature of the rover’s six wheels, said Vandi Verma, senior engineer and rover driver at NASA’s Jet Propulsion Laboratory in Southern California. “A lot of people, when they see the images, don’t appreciate that the wheels are metal. When you’re driving with these wheels on rocks, it’s actually very noisy.”
The second audio clip is a shorter compilation of sounds from the longer recording, processed to remove some of the noise. NASA has previously released audio of the Martian wind and the Perseverance laser zapping rocks to analyse their structure and composition.
The audio adds an extra dimension to the rover’s exploration, said Verma. “The variations between Earth and Mars – we have a feeling for that visually,” she said. “But sound is a whole different dimension – to see the differences between Earth and Mars, and experience that environment more closely.”
Engineers are planning the first flight tests of the Ingenuity Mars Helicopter, after which the Perseverance rover will search for signs of ancient life.
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