'First laser sound': NASA's Perseverance records video, audio of Ingenuity's 4th flight

For the first time, NASA’s Perseverance rover captured the low-pitched whirring of the Ingenuity helicopter's blades and the rotors on the Martian surface, adding a new dimension to the historic Mars project. Using one of its two fitted microphones, NASA’s Perseverance Mars rover recorded the rare sounds of the laser strikes which gives an in-depth idea about the Martian physical properties such as relative hardness and the ambient noise such as the Martian wind.

Perseverance’s new recordings from the surface of Mars were released by NASA across its official social media handles. The audio and the visual footages depict the solar-powered helicopter captured by Perseverance’s Mastcam-Z imager with audio from a microphone belonging to the rover’s SuperCam laser instrument. It would be the fourth flight of the six-wheeled rotorcraft Inguinity on the Red Planet as it keeps achieving milestones. 

"These recordings have demonstrated that our microphone is not only functioning well, but we also have a very high-quality signal for our scientific studies," SuperCam team member Naomi Murdoch, a researcher at the Institut Supérieur de l'Aéronautique et de l'Espace in Toulouse, France, had earlier told a live web conference, when Inguinity captured the first whooshing sounds of martian breeze 2 months ago.

“We're extremely excited about the perspectives and the scientific investigations that we're going to be able to do with the microphone data," Murdoch had said.

In the recent recordings, Perseverance captured the laser zaps rocks from a distance, studying their vapour with a spectrometer to reveal their chemical composition of the Martian land. This truly is a landmark feat, as parked 262 feet (80 meters) from the helicopter’s takeoff and landing spot, the perseverance would not have ‘assuredly’ picked up any sound of the flight, scientists at NASA explained in a release by JPL observatory. “Even during flight, when the helicopter’s blades spin at 2,537 rpm, the sound is greatly muffled by the thin Martian atmosphere,” they further elaborated.

NASA 'refined' the audio to make it clearer

According to NASA, the sound may have been further obscured by Martian wind gusts during the initial moments of the flight. “Listen closely”, NASA wrote, “the helicopter’s hum can be heard faintly above the sound of those winds.”  Scientists refined the audio by isolating the 84-hertz helicopter blade sound, reducing the frequencies below 80 hertz and above 90 hertz, and increasing the volume of the remaining signal. As a result, the helicopter’s hum was loudest when it passed through the field of view of the camera.

The science lead for the SuperCam Mars microphone, Mimoun said: “This a surprise. We had carried out tests and simulations that told us the microphone would barely pick up the sounds of the helicopter, as the Mars atmosphere damps the sound propagation strongly. We have been lucky to register the helicopter at such a distance. This recording will be a gold mine for our understanding of the Martian atmosphere.”