On Mars' far side, NASA has detected subsurface activity: 'Unlike any other incident that has been witnessed
The discoveries might help scientists better comprehend Mars' internal structure, particularly the nature of the planet's core-mantle barrier, according to seismologist Dr Anna Horleston of the University of Bristol and her colleagues.
The largest of the two marsquakes, known as S0976a, occurred on August 25 of last year and seems to have originated in the Valles Marineris, a 2,500-mile-long canyon system four times the depth of the Grand Canyon on Earth.
The existence of cross-cutting fault lines and landslide debris in this location, which had previously been spotted in satellite photographs of the canyon, had hinted that Valles Marineris was geologically active, but this is the first time scientists have clear proof of its seismicity.
The researchers claimed to have detected "PP" and "SS" waves from the magnitude 4.2 event, which are compressional and shear waves that had been reflected at least once off the Martian surface en route to InSight's seismometer, respectively.
"S0976a looks like several of the events we've seen around Cerberus Fossae — a region of substantial faulting — that have depths estimated to be approximately 50 kilometres [31 miles] or more, and it's probable that this event has a similar, deep source mechanism," Dr Horleston added.
The InSight lander as depicted by an artist.
The InSight lander from NASA has discovered two of Mars' greatest seismic shocks.
The magnitudes of the two marsquakes were 4.1 and 4.2, respectively.
Meanwhile, the magnitude 4.1 marsquake occurred 24 days later on September 18 — and it holds the record for being the longest recorded on Mars, lasting 94 minutes.
Over with PP and SS waves, the InSight lander picked up so-called Pdiff waves that travelled along Mars' core-mantle barrier during part of their path from the quake centre to the seismometer, according to data analysis.
Pdiff waves have been observed for the first time by InSight.
The researchers believe that, like S0976a, this second quake, called S1000a, originated on the other side of the earth, but they have yet to pinpoint the exact site.
The waves from S1000a, unlike the low-frequency S0976a, exhibited a relatively wide frequency range.
"The second quake is a distinct outlier in our repertoire," Dr. Horleston stated, "and will be essential to our continued knowledge of Martian seismology."
"This event may have happened near the surface," she continued, since S1000a "has a frequency spectrum much more like a family of events that we witness that have been predicted as shallow, crustal quakes."
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