For the first time, planetary scientists using the automatic station InSight recorded marsquakes on the far side of Mars. Both events turned out to be the largest in magnitude and duration among marsquakes.
What is the purpose of the InSight station?
The InSight station, which landed on Mars in 2018, became the first specialized apparatus for conducting geophysical research on another planet.
Its main scientific instrument at the moment is the SEIS seismograph, which is installed next to the station and has been working for more than three years, recording the seismic activity of the Red Planet.
The analysis of the data obtained allows researchers to test models of the internal structure of Mars and determine the properties of various layers of the planet.
In particular, scientists drew up a diagram of the structure of the subsurface layers of Mars, determined the main boundaries between its layers, estimated the size of the planet’s core, revealed the seasonality of marsquakes, and connected some of them with magma activity in the upper mantle of the planet.
Marsquakes on the far side of Mars
A group of geophysicists led by Anna C. Horleston of the University of Bristol said that for the first time they were able to find seismic events in the SEIS data, the sources of which were located on the opposite side of Mars from the station.
Both new quakes are extremely curious since all previous sources of shocks were concentrated around the Cerberus fault system, which is located not so far from the station. The detected events were designated S0976a and S1000a and were the largest low-frequency marsquakes detected to date.
S0976a was recorded on the night of August 25, 2021, when SEIS recorded the arrival of seismic PP and SS waves. The event had a magnitude of 4.2 and lasted about an hour.
The source of the shocks, according to scientists, was in the Valles Marineris – a giant canyon system in the equatorial part of Mars, about 10 million years old. It was previously predicted that the Valles Marineris could show seismic activity due to collapses, landslides, and faults.
S1000a was recorded on September 18, 2021, it lasted 94 minutes, which was the record for the duration among marsquakes.
The event was characterized by a magnitude of 4.1, while the seismograph, in addition to PP and SS waves, also recorded the arrival of P diff waves with a small amplitude, which, during propagation in the interior of Mars, crossed the boundary between the core and mantle.
It was not possible to precisely localize the source of shocks in this case, but it is known that it is not located near the Olympus Mons Volcano and may be associated with extensive graben systems west of Patera Volcano, which cross the basalt plains.
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• Horleston, A. C., Clinton, J. F., Ceylan, S., Giardini, D., & Charalambous, C. (2022, April 1). The far side of mars: Two distant marsquakes detected by Insight.
• McFadden, C. (2022, April 26). Two enormous “marsquakes” have been detected on the Red Planet. Interesting Engineering.
• Nield, D. (n.d.). The largest marsquakes to date have been detected in the ‘shadow zone’. ScienceAlert.