NASA has released an audio clip of the Ingenuity helicopter's whirring blades as it flew in the thin Martian air for the fourth time on April 30, 2021. The Perseverance rover captured the faint humming sound using one of its two microphones from a distance of 262 feet away from the takeoff and landing area. Mission scientists isolated and amplified the mono 84 hertz helicopter blade sound to make it easier to hear. "This recording will be a gold mine for our understanding of the Martian atmosphere,” said David Mimoun, science lead for the SuperCam Mars microphone.