The Mars probe “InSight” repeatedly registers tremors on the red planet: the device has recorded hundreds of tremors since 2018, although our neighbor is geotectonically considered to be rather tame. On May 4, 2022, she finally detected the strongest marsquake recorded to date. With a magnitude of 4.7, it was also the strongest earthquake ever recorded on another planet. Caroline Beghein from the University of California in Los Angeles and her team have now presented new details about this quake in the “Geophysical Research Letters”.
The tremor lasted more than four hours and released five times more energy than any previously recorded event of this type on Mars. It was weak compared to tremors on Earth, but the energy released was enough to send surface seismic waves all around Mars. For the first time, this phenomenon could be recorded on our neighbor.
“The seismometer on board InSight has recorded thousands of marsquakes, but never one this strong, and it took more than three years from the landing to this event,” says Beghein. “This quake produced several types of waves, including two types that occurred near the surface: what are known as Love waves and Rayleigh waves. Only Rayleigh waves have been observed on Mars, after two impacts, but never during a Marsquake.«
Analysis of this data is helping to decipher the interior of the red planet, which is why detecting and studying this Martian earthquake is particularly important. For example, conclusions can be drawn about the structure, composition and temperatures inside the planet.
The measurements showed that shear waves in the crust move faster when rocks vibrate between 10 and 25 kilometers deep in a direction nearly parallel to the planet’s surface than when the rocks vibrate in a vertical direction.
“This information about the wave speed is related to the deformations in the interior of the crust,” says Beghein. “Altering volcanic rocks and sediment layers that were deposited long ago, or a very large impact, such as a meteoroid, are most likely the cause of the seismic measurements we observed.”
Shear waves also move faster in the southern highland areas of Mars than in the northern lowland areas. The northern hemisphere is lower and cratered. A large lowland impact has been the dominant theory to explain these differences.
The new data indicate that this region may have thick sediment layers with many pores. The gas trapped inside then slows down the seismic waves significantly.
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The original of this article “Mars is shaking – record earthquakes in space” comes from Spektrum.de.