Two Largest Seismic Events On Mars To Date Recorded By NASA's InSight Lander

The seismic events are of magnitudes of 4.2 and 4.1 marsquakes. Also, they are five times stronger than the previous largest event recorded.

The two recent seismic events are the first recorded events to occur on Mars' far side from the InSight lander.

Source : NASA

New Delhi: The two largest seismic events on Mars to date have been recorded by a seismometer on the Red Planet. The seismic events are of magnitudes of 4.2 and 4.1 marsquakes. Also, they are five times stronger than the previous largest event recorded.

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander, which arrived on Mars on November 26, 2018, had placed the seismometer, called Seismic Experiment for Interior Structure (SEIS), on the surface of the Red Planet to measure seismic activity. InSight, the first outer space robotic explorer to study the "inner space" of Mars in depth, also measures tectonic activity and meteorite impacts on the Red Planet.

The two recent seismic events are the first recorded events to occur on Mars' far side from the InSight lander. Researchers from InSight's Marsquake Service (MQS) reported the occurrence of these events in the journal The Seismic Record. The MQS is responsible for prompt review of all seismic data collected by InSight, detection of events that are likely to be of seismic origin, and release of seismic catalogues. By October 2021, the Mars seismic catalogue included 951 events. 

What Are The Two Marsquakes Called?

According to the study, the magnitude 4.2 event is called S0976a, and originated in the Valles Marineris, a massive canyon network that is one of Mars' most distinguishing geological features. A canyon is a deep valley with very steep sides. Valles Marineris is also one the largest graben systems in the Solar System, a statement issued by the Seismological Society of America said. A graven is a depressed segment of the crust of a celestial body bounded on at least two sides by faults. Fractures between two blocks of rocks are called faults. 

Though orbital images of faults and landslides earlier suggested that the area would be seismically active, the recent event is the first confirmed seismic activity in the region.

The magnitude 4.1 event, called S1000a, was recorded 24 days after S0976a. Though the exact location of S1000a could not be determined, the researchers found that it originated on Mars' far side.

The seismic energy from S1000a, which lasted 94 minutes, holds the distinction of being the longest recorded on the Red Planet.

How Are The Two Marsquakes Different?

S0976a and S1000a differ in some important ways. For instance, S0976a is characterised by only low frequency energy, similar to many of the quakes identified so far on Mars. Meanwhile, S1000a has a very broad frequency spectrum, the study said. 

Anna Horleston, the lead author of the study, said that S1000a is a clear outlier in the Mars seismic catalogue, and will be key to further understanding Martian seismology, according to the statement.

She noted that S0976a is likely to have a much deeper origin than S1000a, and looks like many of the events the researchers have located to Cerberus Fossae, which are young tectonic features thousands of kilometres long on the Red Planet. 

Horleston explained that the events located to Cerberus Fossae are estimated to have originated from regions around 50 kilometres deep, and it is likely that S0976a has a similar deep mechanism.

The researchers said that the two new far-side quakes are true outliers. 

Horleston noted that the seismic events are the largest and most distant events, and that they are truly remarkable events in the Martian seismic catalogue.