A magnitude 4.2 and a magnitude 4.1 marsquake were reported by NASA’s InSight lander’s seismometer on Mars. On the planet’s far side, these events are five times more powerful than any other previously observed occurrence.
Data gathered by InSight’s Marsquake Service (MQS) on April 22, 2022, in The Seismic Record, might help scientists better understand the deep layers of Mars, notably its core-mantle boundary.
Scientists from the University of Bristol have discovered that the S0976a earthquake originated in the Valles Marineris, one of Mars’ most distinctive geological features and one of the biggest graben systems ever seen in the Solar System’s history. However, the first definite seismic activity in the area was detected by satellite photographs showing cross-cutting faults and landslides that had been spotted before.
Small-amplitude waves that crossed the core-mantle barrier were seen in S1000a, an earthquake of magnitude 4.1 that occurred 24 days later. The InSight mission has discovered Pdiff waves for the first time. S1000a, like S0976a, was discovered on Mars’ far side, although experts were unable to determine its exact position.
Additionally, the 94-minute duration of S1000a’s seismic activity makes it the longest yet recorded on Mars.
P and S waves can’t go straight to InSight’s seismometer in the core shadow zone because they are blocked or twisted by the core. Both of the marsquakes occurred in this shadow zone. To reach the seismometer, PP and SS waves must be reflected at least once at the surface.
To better comprehend the planet, we need to capture occurrences in the core shadow zone. A co-author from ETH Zürich, Savas Ceylan, claimed that before these two incidents, “the bulk of the seismicity was within around 40 degrees of InSight.” There are places on Mars we have never been able to sample seismologically because the energy is in the core shadow.
These two marsquakes aren’t the same. Many of the earthquakes that have been recorded so far have been low-frequency, while S0976a has a wide range of frequencies. Seismology on Mars would benefit greatly from the inclusion of [S1000a], which Harleston described as “a conspicuous outlier in our inventory.”
That S0976a is more ancient than S1000a was recognized by the researcher. According to our models, shallow crustal earthquakes like this one are more likely to occur near the surface since their frequency spectrum is more similar.
S0976a likely has a similar, deep, source mechanism as many of the events we have identified near Cerberus Fossae, a region of severe faulting, which have depths projected to be approximately 50 kilometers or more.”
Researchers say the two additional far-side quakes observed by InSight are truly outliers compared to the rest of the seismic activity.
“S1000a has a spectrum and duration, unlike any other event, ever witnessed, not to mention being by far the largest and farthest away.” Harleston called the occurrences “exceptional” in the Martian seismic archive.
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