The largest earthquakes detected by InSight data

NASA’s InSight Mars launch vehicle may not be as well known as its relatives the rover Perseverance and Curiosity, but it does important work to better understand the interior of Mars and how the planet is shaken seahorses. Now researchers have identified the two biggest tremors seen to date.

A study published in the journal Seismic record, describes how two earthquakes were discovered from InSight data. The first occurred on August 25, 2021, and the second shortly thereafter on September 18, 2021. These two events were significant for a number of reasons: first, they were the largest tremors identified to date, and second, they occurred in the far side of Mars from InSight, while most of the detected earthquakes originated closer to the landing craft.

The August earthquake, named S0976a, had a magnitude of 4.2, and the September earthquake, named S1000a, had a magnitude of 4.1. This makes them five times stronger than previously detected seaquakes. The first quake lasted a typical period of a few seconds, but the second event lasted a long time, a total of 94 minutes, making it the longest event recorded so far. It also had an unusually wide frequency, which means that its energy spread over frequencies from 0.1 Hz to 5 Hz.

“They are not only the largest and most remote events by a significant margin, but the S1000a also has a spectrum and duration unlike any other event observed before,” said lead researcher Anna Horlston. statement. “These are really great events in the Martian seismic catalog.”

The first earthquake is particularly interesting because it was found that it occurred in the village Valles Marineris Canyon Network. Earlier, researchers predicted that there would be seismic activity in the region, but they first found it there. Instead, most sea tremors have been found to date originates in the Cerberus region.

These earthquakes originated on the far side of the planet from the InSight lander, in an area called the shadow zone. This is the area from which seismic waves (so-called P and S waves) cannot travel directly to the landing craft because the planet’s core interferes. To determine the origin of an earthquake, researchers must look at the mapping of these waves (so-called PP and SS waves).

The ability to detect earthquakes from this area is a major achievement of seismology on Mars. “Recording events in the main shadow zone is a real stepping stone to our understanding of Mars. Prior to the two events, most of the seismicity was within about 40 degrees of InSight, ”said Savas Ceylan, co-author of ETH Zürich. “Being in the shadow of the nucleus, energy travels through parts of Mars that we have never been able to select seismologically before.”

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