Largest quakes ever recorded on Mars could reveal more about the Red Planet’s interior

Nasa has reported the two largest quakes ever recorded on Mars, and scientists say studying them “will be instrumental in furthering our understanding” of the planet.

A seismometer put on the Red Planet by the space agency’s InSight lander recorded the two largest so-called marsquakes ever, of magnitude 4.2 and 4.1. The events have been dubbed S0976a and S1000a, in a study published inThe Seismic Record on 22 April.

This is the first time waves from marsquakes have been spotted by the InSight lander mission, which reached the Martian surface in November 2018.

One of the quakes was described by study co-author Anna Horleston, from the University of Bristol in the UK, to be “unlike any other event previously observed”.

“Not only are they the largest and most distant events by a considerable margin, S1000a has a spectrum and duration unlike any other event previously observed. They truly are remarkable events in the Martian seismic catalogue,” Dr Horleston said.

Researchers said the quakes are five times stronger than the previous ones recorded.

Data from these quakes could help scientists learn more about the interior layers of Mars, particularly its core-mantle boundary, said researchers from InSight’s Marsquake Service (MQS).

Marsquake waves from S0976a were found to have originated in the Valles Marineris, a massive canyon network that is one of Mars’ most distinguishing geological features and is one of the largest graben systems in the Solar System.

While previous studies have suggested the area would be seismically active, the new report details the first confirmed seismic activity there.

The S1000a event was recorded 24 days after the 4.2 magnitude quake and was characterised by waves, some of which were of small amplitude, traversing the Red Planet’s core-mantle boundary.

Researchers said the quakes differed in their frequencies, with S0976a characterised by only a low-frequency energy, while S1000a had a very broad frequency spectrum.

“[S1000a] is a clear outlier in our catalogue and will be key to our further understanding of Martian seismology,” Dr Horleston said, adding that it may have occurred near the surface.

While researchers could not pinpoint S1000a’s particular origin, they said it came from Mars’ far side and added that the seismic energy from the event now holds the distinction of being the longest recorded on Mars, lasting 94 minutes.

On the other hand, researchers said S0976a seems like many of the events revolved around the Cerberus Fossae – an area of extensive faulting on Mars that has depths modeled to be around 50km or more.

Both the seismic events occurred in a region of Mars where the quakes’ primary and secondary waves cannot travel directly to InSight’s seismometer as they are stopped or bent by the planet’s core.

“Recording events within the core shadow zone is a real steppingstone for our understanding of Mars. Prior to these two events the majority of the seismicity was within about 40 degrees distance of InSight,” Savas Ceylan, a co-author of the study from ETH Zurich, said in a statement.

“Being within the core shadow, the energy traverses parts of Mars we have never been able to seismologically sample before,” Dr Ceylan added.

Scientists said the two quakes are “true outliers” in the catalog of seismic activity recorded on the Red Planet so far. “S0976a and S1000a are remarkable events in the Martian seismic catalogue, and they will be instrumental in furthering our understanding of the red planet,” the scientists wrote in the study.