The Seismic Experiment for Interior Structure (SEIS), a highly sensitive seismometer onboard NASA’s InSight lander, was designed to listen for marsquakes. Out of more than 100 events detected to date, about 21 are strongly considered to be the quakes. The remainder could be marsquakes as well, but members of the InSight science team hasn’t ruled out other causes.
NASA’s InSight lander placed its seismometer on Mars on December 19, 2018. Image credit: NASA / JPL-Caltech.
Put on headphones to listen to the sounds of two marsquakes detected by the SEIS instrument.
These events occurred on May 22, 2019 (the 173rd Martian day, or sol, of the mission) and July 25, 2019 (Sol 235).
Far below the human range of hearing, these sonifications had to be speeded up and slightly processed to be audible through headphones.
“The Sol 173 quake was about a magnitude 3.7, the Sol 235 quake was about a magnitude 3.3,” the InSight researchers said.
“Both events suggest that the Martian crust is like a mix of the Earth’s crust and the Moon’s.”
“Cracks in Earth’s crust seal over time as water fills them with new minerals. This enables sound waves to continue uninterrupted as they pass through old fractures.”
“Drier crusts like the Moon’s remain fractured after impacts, scattering sound waves for tens of minutes rather than allowing them to travel in a straight line.”
“Mars, with its cratered surface, is slightly more Moon-like, with seismic waves ringing for a minute or so, whereas quakes on Earth can come and go in seconds.”
The SEIS instrument has no trouble identifying quiet quakes, but its sensitive ear means the scientists have lots of other noises to filter out.
And while some are trickier than others to spot, they all have made InSight’s presence on Mars feel more real to those working with the spacecraft.
The InSight science team members found that the twilight hours are one of the best times to hunt for marsquakes.
During the day, sunlight warms the air and creates more wind interference than at night.
Evening is also when peculiar sounds that the researchers have nicknamed ‘dinks and donks’ become more prevalent.
“We know they’re coming from delicate parts within SEIS expanding and contracting against one another and thinks heat loss may be the factor, similar to how a car engine ‘ticks’ after it’s turned off and begins cooling,” the team members said.
“You can hear a number of these ‘dinks and donks,’ recorded just after sundown on July 16, 2019 (Sol 226).”
“It’s been exciting, especially in the beginning, hearing the first vibrations from the lander,” said InSight science team member Dr. Constantinos Charalambous, a researcher at Imperial College London.
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This article is based on text provided by the National Aeronautics and Space Administration.
