Mars has air that is about 1% as thick as Earth's. This is so weak that you may not hear that someone is talking to you from a distance.
Yet, wind and tornado-like dust devils waft across the surface of Mars, and recording the sounds of these phenomena is essential to the success of NASA's latest mission on the red planet.
NASA landed its InSight probe on November 26 in a flat Martian plane. The probe misses its landing site with a robotic arm and a set of instruments to help the managers of the $ 830 million robot plan their next moves.
One of the lander's biggest goals is to listen to seismic rumblings called "Mars quakes". NASA researchers said during a press conference Friday that the vibration sensor tool from InSight is so sensitive that the wind can affect the readings. This can happen when wind blows against the instrument itself or when the lander's solar panels are constantly moving.
InSight's robotic arm will eventually place the seismometer – a dome-shaped instrument called SEIS – on the surface of Mars. But now it's still on the top deck of the car the size of a car.
"It's a bit like a flag waving in the wind," said Thomas Pike, the senior scientist behind the SEIS instrument and an engineer at Imperial College London, during the briefing.
NASA converted the SEIS readings to audio, described in a press release called the "harsh low rumble" caused by 10-15 miles per hour of Mars breeze. An air pressure sensor on the spacecraft's deck also recorded the sounds of the wind on Mars.
Although the raw data from the air pressure sensor are inaudible, they are audible by a factor of 100 when accelerated.
"Listening to the noise of the pressure sensor reminds me to sit outside on a windy summer afternoon," said Don Banfield, a planetary scientist and member of Cornell University's InSight team, during the briefing. "In a way, it sounds like you're sitting on the InSight lander on Mars."
You can hear the original sounds in the video below. If you do not have a subwoofer or hi-fi headphone, NASA has also developed a higher pitch version.
Pike said that images of Mars remind him of deserts on Earth, but hearing Mars is completely different.
"Our ear just is not set to recognize what we hear," Pike said during the briefing. "It really sounds beyond."
More importantly, Pike said that InSight scientists need to record as much noise as possible so they can shut them down and ensure the future success of the mission.
"There may be a Martian earthquake on the other side of the planet right now and we would not hear it over the wind chatter," he said. "So we really want to be able to hear the inside of Mars over this chatter."
By gathering good data about the ground vibrations of Mars, scientists could find out the inner structure of Mars. This information would give them a clue to how the world has turned into a desert planet instead of a fertile blue-green marble like Earth.
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Dust devil hear from afar?
Another obvious discovery that scientists have already made by listening to Mars with InSight instruments, all of which are not yet fully used, is the close passing of dust devils.
Dust devils are whirling whirlwinds that rip across Mars at about 60 km / h. They are not very powerful because of the low air density, but they are strong enough to clear dust from the solar panels of clumsy human spacecraft.
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seen from the orbit of Mars.
Pike, Banfield, and other members of the InSight team believe that some of the very low-frequency vibrations that SEIS has picked up reveal where dust devils have recently blown around.
NASA was even able to determine the path of Dust devils across the surface, as shown below by thin lines from northwest to southeast.
"I think this will be the most studied point on Mars," says Bruce Banerdt, a planetary geologist at Jet Propulsion NASA Laboratory, the leader of the InSight mission, said Friday at the briefing. He added that the spacecraft is effectively "the best weather station ever placed on the surface of Mars".
NASA will spend a few more weeks recording the blowing wind (to learn how best to extinguish these sounds) and measuring InSight's landing pads. Then it will decide where to place the seismometer and a hammer near heat sensor, and the two-year mission will begin in earnest.