An artist’s illustration of the InSight lander on Mars, with its “mole” burrowed deep in the soil. ​​NASA/JPL-Caltech

NASA’s InSight lander has observed more than 500 Mars quakes since it landed on the red planet in 2018. But there’s a glaring hole in its catalogue: The lander has yet to detect any big rumblings.

“We would have expected a few magnitude 4 events, and maybe even a magnitude 5 at this point, given the number of smaller quakes,” Bruce Banerdt, the principal investigator for InSight, told Insider.

Instead, most of the quakes have been so quiet that the average Californian wouldn’t even notice them. The four biggest Mars quakes InSight’s seismometer has felt ranged in magnitude from 3.1 to 3.6.

So Mars seismologists are beginning to scratch their heads.

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