From The Editors Science

The “Sounds of Mars” – NASA’s InSight Lander “Hears” Martian Winds

Within a week of its picture-perfect landing on Mars, NASA’s InSight lander captured the first sounds from the Red Planet, pleasantly surprising the InSight team at the space agency’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

In the absence of a microphone, InSight’s supersensitive onboard seismometer called SEIS – the acronym for Seismic Experiment for Interior Structure – managed to pick up vibrations from gusts of Martian wind blowing across the lander’s solar panels at 10 mph to 15 mph (16 kph to 24 kph).

In time, the lander’s robotic arm will place SEIS on the ground where it will collect vibrations emanating from deep inside Mars, giving scientists unprecedented data that will help them learn more about the mysterious planet.

The sounds of the alien breeze were also detected and, in fact, directly recorded by the air pressure sensor on the Auxiliary Payload Sensor Subsystem (APSS) – another vital piece of mission hardware that’s designed to collect meteorological data.

The very low-pitch sounds released by NASA are barely audible until the agency pitches up the SEISS audio by a couple of octaves and speeds up the APSS data by a factor of 100, thereby increasing its frequency 100 times.

To be honest, it kind of spooks you somewhat; it’s the ideal background sound-effect for a horror movie – it’s, well, out of this world.

Check it out for yourself in this video here (Credit: NASA/JPL-Caltech/CNES/IPGP/Imperial College/Cornell).

“Capturing this audio was an unplanned treat,” said Bruce Banerdt, InSight principal investigator at JPL.

“But one of the things our mission is dedicated to is measuring motion on Mars, and naturally that includes motion caused by sound waves,” he said.

“To me, the sounds are really unworldly,” Banerdt also said.

“They do sound like the wind or maybe the ocean kind of roaring in the background. But it also has an unworldly feel to it,” he added.

Tom Pike, a sensor designer at Imperial College London and an InSight science team member, said:

“The InSight lander acts like a giant ear. The solar panels on the lander’s sides respond to pressure fluctuations of the wind.

“It’s like InSight is cupping its ears and hearing the Mars wind beating on it.
“When we looked at the direction of the lander vibrations coming from the solar panels, it matches the expected wind direction at our landing site.”

Pike gave the analogy of a flag in the wind to further explain the APSS recording, saying that when a flag obstructs the flow of wind, it causes fluctuations in air pressure that comes across to the human ear as the flapping sound that you associate with a flag in breezy conditions.

“That’s literally what sound is — changes in air pressure,” said InSight’s science lead for APSS Don Banfield (Cornell University in Ithaca, New York).

“You hear that whenever you speak to someone across the room.”

While this is a big first for NASA, it says we can expect even better sound from the planet in about two years when its Mars 2020 probe lands there with two onboard microphones.

One of the microphones will “specifically” record the sounds generated during the Mars landing, while the other, which is part of a SuperCam, “will be able to detect the sound of the instrument’s laser as it zaps different materials,” which “will help identify these materials based on the change in sound frequency.”

On Nov 26, after traveling for nearly seven months and more than 300 million miles through deep space, InSight finally entered the Martian atmosphere at 2:47 pm ET, beginning the entry, descent and landing (EDL) phase of the mission.

The EDL began with the lander plunging into the thin Martian atmosphere at 12,300 miles per hour, with just about seven minutes at its disposal to decelerate to a touchdown speed of 5mph.

Two minutes into the decent, InSight’s protective heat shield had reached peak heating of 2,700 degrees Fahrenheit (1,482 Celsius), causing a brief weakening of the lander’s radio signal.

Then began InSight’s decelerating maneuvers, with the parachute deploying first, followed by the heat shield jettisoning – all of this happening within three minutes of entry.

The descent slowed, but not enough, as the probe was still doing around 180 miles per hour.

This is when the lander deployed its tripod legs, got rid of the back shell and fired the retro rockets, coming to rest on the equatorial plane of Elysium Planitia at 2:54 p.m. ET, successfully completing the EDL sequence.

In addition to SEIS and APSS, there’s a plethora of other scientific instruments, including the Heat Flow and Physical Properties Package, featuring a “self-hammering nail” capable of penetrating 5 meters into the planet’s crust to read the heat flow pattern inside Mars.

“Landing was thrilling, but I’m looking forward to the drilling,” an excited Banerdt had said in a post-landing statement.

“When the first images come down, our engineering and science teams will hit the ground running, beginning to plan where to deploy our science instruments,” he said.

Also on board were two experimental CubeSats – MarCO-A and MarCO-B – that actually beamed back data about InSight as it entered the Martian atmosphere last week.

The windy soundbite captured on Dec 1 is more than what Banerdt and his team were hoping for.

Nasa’s acting director of planetary science Lori Glaze couldn’t have put it better when she said:

“We’re all still on a high from the landing last week…and here we are less than two weeks after landing, and we’ve already got some amazing new science. It’s cool, it’s fun.”

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