On December 1, 2018, NASA’s InSight lander captured a haunting low rumble caused by vibrations from the Martian wind, estimated to be blowing between 10 to 15 mph (5-7 m/sec) from northwest to southeast. The wind was consistent with the direction of dust devil streaks in the landing area, which were observed from orbit.
“Capturing this audio was an unplanned treat. But one of the things our mission is dedicated to is measuring motion on Mars, and naturally that includes motion caused by sound waves,” said InSight principal investigator Dr. Bruce Banerdt, a researcher at NASA’s Jet Propulsion Laboratory.
The vibrations caused by the Martian wind were detected by two very sensitive sensors on InSight: an air pressure sensor inside the lander and a seismometer sitting on the lander’s deck.
The air pressure sensor, part of the Auxiliary Payload Sensor Subsystem (APSS), which will collect meteorological data, recorded these air vibrations directly.
The seismometer, called the Seismic Experiment for Interior Structure (SEIS), recorded lander vibrations caused by the wind moving over the spacecraft’s solar panels, which are each 7 feet (2.2 m) in diameter and stick out from the sides of the lander like a giant pair of ears.
This image from InSight’s robotic-arm mounted Instrument Deployment Camera shows the instruments on the spacecraft’s deck, with the Martian surface of Elysium Planitia in the background. The color-calibrated picture was acquired on December 4, 2018 (Sol 8); in the foreground, a copper-colored hexagonal cover protects the SEIS seismometer; the gray dome behind SEIS is the wind and thermal shield, which will be placed over SEIS; to the left is a black cylindrical instrument, the Heat Flow and Physical Properties Probe (HP3); HP3 will drill up to 16 feet (5 m) below the Martian surface, measuring heat released from the interior of the planet; above the deck is InSight’s robotic arm, with the stowed grapple directly facing the camera; to the right can be seen a small portion of one of the two solar panels that help power InSight and part of the UHF communication antenna. Image credit: NASA / JPL-Caltech.
This is the only phase of the mission during which SEIS will be capable of detecting vibrations generated directly by the lander.
In a few weeks, it will be placed on the Martian surface by InSight’s robotic arm, then covered by a domed shield to protect it from wind and temperature changes. It still will detect the lander’s movement, though channeled through the Martian surface.
For now, it’s recording vibrational data that the mission team later will be able to use to cancel out noise from the lander when SEIS is on the surface, allowing them to detect better actual marsquakes.
“The InSight lander acts like a giant ear,” said InSight team member Dr. Tom Pike, a researcher at Imperial College London.
“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.”
A partial view of InSight’s deck, where it stands on the Martian plains Elysium Planitia; the color-calibrated image was received on December 4, 2018 (Sol 8); InSight’s robotic arm with its stowed grapple can be seen above the deck, and jutting out from the front of the deck is one of the boxy attitude control system thrusters that helped control the spacecraft’s landing; the circular silver inset of the propellant tank can also be seen in the middle of the image, as well as one of the connections for the aeroshell and parachute, which looks like a cupholder in the foreground; next to the propellant tank is the UHF antenna, which helps the lander communicate with Earth; in the background, part of one of InSight’s solar panels is visible. Image credit: NASA / JPL-Caltech.
In addition to the audio samples, InSight captured new images showing its robotic arm.
With a reach of nearly 6 feet (2 m), the lander’s arm will be used to pick up science instruments from its deck, gently setting them on the Martian surface at Elysium Planitia.
“Today we can see the first glimpses of our workspace,” Dr. Banerdt said.
“By early next week, we’ll be imaging it in finer detail and creating a full mosaic.”
