The low-pitched whirring of the Ingenuity helicopter's blades as it passes through the rarefied Martian atmosphere has been captured for the first time by NASA's Perseverance rover.
The space agency released new footage of its rotorcraft companion's fourth flight on April 30 shot by the six-wheeled robot, this time with an audio track, on Friday.
The nearly three-minute video starts with the low rumble of wind blowing across the Jezero Crater, where Perseverance landed in February on a trip to look for ancient microbes.
The helicopter blades' low hum, which rotate at over 2,500 revolutions per minute, is scarcely audible. It almost sounds like a low-pitched mosquito or other flying insect from a long distance. That's because the Perseverance rover's microphone was more than 260 feet (80 metres) away from the 4-pound (1.8-kilogram) helicopter. The chopper's sound was distorted by the rumbling wind gusts. The sound of the whirring blades was separated and magnified by scientists, making it easier to hear.