The spacecraft is equipped with an incredibly sensitive seismometer called the Seismic Experiment for Interior Structure (SEIS), which is designed to listen for marsquakes. By examining how seismic waves move through the planet's interior, scientists hope to learn more about Mars' deep inner structure.
InSight placed the seismometer on Mars' surface in December, but it took until April for the instrument to detect the first likely marsquake. More than 100 events have been detected, and around 21 of them are "strongly considered to be quakes," NASA says.
The space agency shared sounds from two quakes detected by SEIS: one that happened on May 22 and another that took place July 25. They're around magnitude 3.7 and 3.3, respectively.
The subtle rumbles are below the human range of hearing but were sped up and processed so they could be heard through headphones. They both suggest the crust on Mars resembles a mix of the Earth's crust and the moon's.
On Earth, cracks in the crust seal over time after water fills them with new minerals. Sound waves can therefore travel uninterrupted when they go through old fractures, NASA says. The moon's crust, on the other hand, stays fractured, and sound waves scatter for several minutes. The cratered surface of Mars is more similar to the moon's, and seismic waves go on for about a minute. Quakes on Earth, on the other hand, can come and go in seconds.
"It's been exciting, especially in the beginning, hearing the first vibrations from the lander," Constantinos Charalambous, an InSight science team member at Imperial College London, said in the post. "You're imagining what's really happening on Mars as InSight sits on the open landscape."
Because SEIS is so sensitive to sounds, scientists have to filter out other noises it picks up, like wind gusts. The team found that looking for quakes at night can be more effective because during the day, sunlight warms the air and causes more wind interference.
In December, NASA also shared.
First published Oct. 1.
Update, Oct. 2, 1:59 p.m PT: Adds more information on SEIS.