On April 30, 2021, NASA’s Perseverance rover made history as the first spacecraft to record sounds from another spacecraft on another planet. During Ingenuity’s fourth flight, a microphone included with the SuperCam instrument aboard Perseverance captured the humming sound of the blades and the din of wind.
For the first time, a spacecraft on another planet has recorded the sounds of a separate spacecraft. NASA’s Perseverance Mars rover used one of its two microphones to listen as the Ingenuity helicopter flew for the fourth time on April 30, 2021. A new video combines footage of the solar-powered helicopter taken by Perseverance’s Mastcam-Z imager with audio from a microphone belonging to the rover’s SuperCam laser instrument.
The laser zaps rocks from a distance, studying their vapor with a spectrometer to reveal their chemical composition. The instrument’s microphone records the sounds of those laser strikes, which provide information on the physical properties of the targets, such as their relative hardness. The microphone can also record ambient noise, like the Martian wind.
With Perseverance parked 262 feet (80 meters) from the helicopter’s takeoff and landing spot, the rover mission wasn’t sure if the microphone would pick up any sound of the flight. Even during flight, when the helicopter’s blades spin at 2,537 rpm, the sound is greatly muffled by the thin Martian atmosphere. It is further obscured by Martian wind gusts during the initial moments of the flight. Listen closely, though, and the helicopter’s hum can be heard faintly above the sound of those winds.
Scientists made the audio, which is recorded in mono, easier to hear 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. Some frequencies were clipped to bring out the helicopter’s hum, which is loudest when the helicopter passes through the field of view of the camera.