Sylvie Claire / May 8, 2021
Nasa released for the first time on Friday a recording of the sound of the Ingenuity helicopter blades, which made its fifth successful flight, in the rarefied air of Mars, taken by the Perseverance rover.
The U.S. space agency posted new footage from the six-wheeled robot's April 30 Ingenuity flight on its Twitter account, this time with sound. The nearly three-minute video begins with the wind blowing over Jezero Crater, where Perseverance landed on Feb. 18 with a mission to search for evidence of ancient life. - 2,400 revolutions per minute - Ingenuity then takes off, and we hear the thud of its blades turning at nearly 2,400 revolutions per minute for a total of 260 meters round trip. Nasa engineers did not know if the sound could be recorded, as Perseverance is about 80 meters from the takeoff and landing site. The Martian atmosphere, composed of 96% carbon dioxide, is only 1% as dense as Earth's, making the sounds much more muted. This is a very good surprise, said David Mimoun, professor of space systems and planetary science at the Institut Supérieur de l'Aéronautique et de l'Espace (ISAE-SUPAERO) in Toulouse, southwest France.
We had done tests and simulations that made us think that the microphone could barely hear the sound of the helicopter, because the atmosphere of Mars limits the propagation of sound, he explained. Perseverance has a SuperCam that uses laser analysis of rocks to help determine the chemical and mineralogical composition of the Red Planet's surface. The instrument has a microphone that records the sound of the laser as it hits its targets, which sounds like a clatter, giving additional information such as their hardness. The Ingenuity flight recording is a gold mine for understanding the Martian atmosphere, said David Mimoun. Nasa made it easy to listen to the flight, recorded in mono, by isolating sounds at 84 hertz, then reducing sounds below 80 and above 90 hertz, while increasing the volume of sounds in between. For Soren Madsen, director of Perseverance development at Nasa's propulsion laboratory, this recording is an example of how instruments sent to Mars can complement each other.
Quest for life - The SuperCam, partly designed by French engineers, had broadcast a first recording of Martian winds shortly after landing. Nasa also announced Friday the success of the 5th flight of Ingenuity, which had 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 it did on its first four trips. This trip marks the beginning of a new role for Ingenuity: after proving that it is possible to fly on Mars, it will now assist Perseverance in its main mission, the search for ancient life on the Red Planet, for example by exploring places of scientific interest that are inaccessible by car, or by finding the safest route. This type of operation also aims to evaluate the capacity of such flying machines to assist future human explorers. Nasa engineers had announced a week ago to extend by one month the mission of the helicopter, which proved to be more solid than expected. However, it was not designed for a very prolonged activity and the repeated cycles of freezing and thawing could damage the small aircraft. Nasa anticipates two more flights over the next 30 days.