Sounds of space: Nasa's Mars helicopter heard humming through thin Martian air

First came the amazing pictures, then the video. Now Nasa is sharing sounds of its little helicopter humming through the thin Martian air.

Nasa's Jet Propulsion Laboratory in California released this first-ever audio, just before Ingenuity was set to soar on its fifth test flight.

The low hum from the helicopter blades spinning at more than 2500 revolutions per minute is barely audible. It almost sounds like a low-pitched, far-away mosquito or other flying insect.

That's because the 1.8kg helicopter was more than 80m from the microphone on the Perseverance rover. The rumbling wind gusts also obscured the chopper's sound.

Scientists isolated the sound of the whirring blades and magnified it, making it easier to hear.

The sound was recorded during the helicopter's fourth test flight on April 30.

The Mars Ingenuity helicopter flies over the surface of the planet. Photo / AP

Ingenuity — the first powered aircraft to fly at another planet — arrived at Mars on February 18, clinging to Perseverance's belly. Its first flight was April 19; Nasa named the takeoff and landing area Wright Brothers Field in honour of Wilbur and Orville, who made the world's first airplane flights in 1903. A stamp-size piece of wing fabric from the original Wright Flyer is aboard Ingenuity.

The $116 million tech demo was supposed to end a few days ago, but Nasa extended the mission by at least a month to get more flying time.

Friday afternoon's test flight was aiming for twice the altitude — as high as 10m. The helicopter was also headed to a new touchdown spot.

With the helicopter's first phase complete, the rover can now start hunting for rocks that might contain signs of past microscopic life. Core samples will be collected for eventual return to Earth.

-AP