NASA’s Perseverance rover has for the first time captured
the low-pitched whirring of the Ingenuity helicopter’s blades as it flies
through the rarefied Martian atmosphere.
اضافة اعلان
The space agency on Friday released new footage shot by the
six-wheeled robot of its rotorcraft companion making its fourth flight on April
30 — this time accompanied by an audio track.
The nearly three-minute-long video begins with the low
rumble of wind blowing across the
Jezero Crater, where Perseverance landed in
February on a mission to search for signs of ancient microbes.
Ingenuity takes off, and its blades can be heard humming
softly as they spin at nearly 2,400 rpm on the 262-meter roundtrip.
The mission’s engineers weren’t sure they would pick up the
flight sound at all, given that Perseverance was parked 262 feet (80 meters)
away from the takeoff and landing spot.
The Martian atmosphere is about one percent the density of
our planet’s, making everything much quieter than on Earth.
“This is a very good surprise,” said David Mimoun, a
professor of planetary science at Institut Superieur de l’Aeronautique et de
l’Espace (ISAE-SUPAERO) in Toulouse, France, and science lead for the SuperCam
Mars microphone.
“We had carried out tests and simulations that told us the
microphone would barely pick up the sounds of the helicopter, as the Mars
atmosphere damps the sound propagation strongly,” he added.
The SuperCam is an instrument on board Perseverance that
laser-zaps rocks from a distance, in order to study their vapor with a device
called a spectrometer that reveals their chemical composition.
It also comes with a microphone to record the sounds, which
yields additional insights into the physical properties of the targets, like
how hard they are.
Similarly, explained Mimoun, the new recording of
Ingenuity’s flight “will be a gold mine for our understanding of the Martian
atmosphere.”
Apart from having a lower volume, sounds emitted on Mars
travel slower than they do on Earth, because of cold temperatures, which
average -63°C on the surface.
The speed of sound on the planet is therefore around 240
meters per second, compared to about 340 meters per second here.
The atmosphere of Mars, made up of 96 percent carbon
dioxide, tends to absorb higher-pitched sounds, so only lower-pitched sounds
can travel long distances.
NASA enhanced the audio, which was recorded in mono, by
isolating the pitch of the helicopter blades at 84 hertz, and reducing audio at
frequencies below 80 and above 90 hertz. They then increased the volume of the
remaining signal.
Soren Madsen, Perseverance payload development manager at
NASA’s Jet Propulsion Laboratory, said the recording was an example of how the
mission’s instruments are able to work in tandem to enhance our understanding
of the Red Planet.
As Ingenuity moves away from Perseverance and out of shot,
the pitch decreases and as it returns the pitch increases.
This is known as the Doppler Effect, and it provides an
additional layer of confirmation of the helicopter’s flight path when it is out
of visual range.
Ingenuity made the first powered, controlled flight on
another planet on April 19, and flew a fifth time on Friday at 7:26pm GMT.
After receiving telemetry data several hours later,
NASA confirmed the flight’s success on Twitter, posting a new picture of the chopper
taken from Perseverance.
Friday’s sortie was Ingenuity’s first one-way trip, setting
the stage for it to begin a new job as Perseverance’s scout.
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