NASA’s Mars Insight probe may not be as well known as Perseverance and others, but it is doing important work in understanding more about the interior of Mars, and how it is shaken by swamps, as researchers have identified two of the largest earthquakes seen so far.
The research, published in The Seismic Record, describes how two earthquakes were detected from InSight data. The first occurred on August 25, 2021, and the second occurred shortly after on September 18, 2021.
These two events were important for a number of reasons: first, they were the largest earthquakes ever detected, and second, they occurred at the extremes. The Martian side of InSight, while most of the earthquakes detected near the probe, Digitartlends reported.
The August earthquake, called S0976a, had a magnitude of 4.2, while the September earthquake, called the S1000a, had a magnitude of 4.1, making it five times more powerful than previously detected earthquakes.
The first earthquake lasted a typical period of a few seconds, but the second event lasted for a long time, recording 94 minutes in total, making it the longest event recorded so far. It also has an unusually wide frequency, meaning that its energy is spread across frequencies of 0.1 Hz to 5 Hz.
“Not only are they the largest and most distant events by a significant margin, S1000a has a spectrum and duration unlike any other previously observed event,” lead researcher Anna Hurleston said in a statement.
The first earthquake is particularly interesting as it was found to have originated in the Valles Marineris Valley network. Researchers had previously predicted that there would be seismic activity in this area, but this is the first time they actually detected it there. Instead, most of the marsh earthquakes detected so far originated. In the Cerberus Fossae region.
These earthquakes originated on the far side of the planet from the InSight lander, in a region called the core shadow region, this is the region from which seismic waves (called P and S waves) cannot travel directly to the probe, because the planet’s core obstructs the way, to discover the origin of Earthquake researchers have to look at the reflections of these waves instead (called PP and SS waves).
Being able to detect earthquakes coming from this region is a major breakthrough in Mars seismology, “Recording events within the core shadow region is a real starting point for our understanding of Mars.
Prior to these two events, the majority of seismic activity was within about 40 degrees of InSight,” said Savas Ceylan, co-author of the paper from ETH Zürich, “Being within the primary shadow, the energy crosses parts of Mars that we haven’t been able to seismically sample before.”