Washington (AFP)

NASA made public for the first time on Friday a recording of the sound of the blades of the Ingenuity helicopter, which made its fifth flight, in the rarefied air of Mars, taken by the rover Perseverance.

The US space agency posted on its Twitter account new images taken by the six-wheeled robot from Ingenuity's flight on April 30, this time accompanied by sound.

The nearly three-minute video begins with the wind blowing over Jezero Crater, where Perseverance landed on February 18 on a mission to search for traces of ancient life.

- 2,400 revolutions per minute -

Ingenuity flies away then, and we hear the thud of its blades which turn at nearly 2,400 revolutions per minute for a round trip of 260 meters in total.

NASA engineers were unsure whether the sound could be recorded, as Perseverance was about 80 meters from the take-off and landing location.

The Martian atmosphere, made up of 96% carbon dioxide, has a density of only 1% that of Earth, which makes noises much more muffled.

"It's a very good surprise," said David Mimoun, professor of space systems and planetary science at the Higher Institute of Aeronautics and Space (ISAE-SUPAERO) in Toulouse, in the southwest of France. France.

"We had done tests and simulations that made us think that the microphone could hardly hear the sound of the helicopter, because the atmosphere of Mars limits the propagation of sound," he explained.

Perseverance has a SuperCam that laser analyzes rocks to help determine the chemical and mineralogical makeup of the Red Planet's surface.

This instrument has a microphone that records the sound of the laser when it hits its targets, which resembles that of a clicking noise, giving additional elements such as their harshness.

The recording of Ingenuity's flight "is a gold mine for understanding the Martian atmosphere," said David Mimoun.

NASA made it easier to listen to the flight, recorded in mono, by isolating noise at 84 hertz, then reducing sounds below 80 and above 90 hertz, while increasing the volume of sounds between these two frequencies. .

For Soren Madsen, director of development for Perseverance at the NASA propulsion laboratory, this recording is an example of the complementarity of instruments sent to Mars.

- Quest for life -

The SuperCam, partly designed by French engineers, had broadcast a first recording of Martian winds shortly after landing.

NASA also announced on Friday the success of Ingenuity's 5th flight, which made history on April 19 by making the first flight of a motorized vehicle on another planet.

This time, the helicopter made its first one-way trip, instead of returning to its starting point as on its first four trips.

This journey marks the start of a new role for Ingenuity: after proving that it is possible to fly on Mars, he will now assist Perseverance in its main mission, the quest for ancient life on the red planet, by going for example explore places of scientific interest, inaccessible by driving, or by finding the safest path.

This type of operation also aims to assess the ability of such flying devices to assist future human explorers.

NASA engineers announced a week ago to extend the helicopter's mission by one month, which turned out to be more solid than expected.

However, it was not designed for very prolonged activity and repeated cycles of freeze and thaw could damage the small device.

NASA anticipates two more flights over the next 30 days.

© 2021 AFP