NASA InSight Study Reveals Mysteries About Mars' Liquid Iron Core, Gives Its Clearest Look Ever

The two quakes occurred after InSight had been functioning on Mars for more than a full Martian year, which is equivalent to about two Earth years, and one of them was caused by a meteoroid impact. 

NASA's retired InSight Mars lander has provided the clearest look ever of the Martian core, and revealed new mysteries about it. Although the lander retired in December 2022, scientists are still exploring its treasure trove of data to unearth new secrets. In 2021, InSight's seismometer detected seismic waves from a pair of temblors (quakes). By studying these seismic waves, scientists deduced that the liquid iron Martian core is smaller and denser than previously thought. 

The study describing the findings was published April 24 in the Proceedings of the National Academies of Sciences. It marks the first direct observations ever made of another planet's core.

When and where did the quakes occur on Mars?

One of the temblors occurred on August 25, 2021, and the other happened on September 18, 2021. The InSight team first identified these temblors to have originated on the side of Mars opposite to the lander. The temblors were far-side quakes. The distance made the detection of seismic waves difficult. This is because the farther a quake occurs from InSight, the deeper into the planet its seismic waves can travel before being detected. 

In a NASA statement, Jessica Irving, the lead author on the paper, said the researchers needed both luck and skill to find, and then use, the quakes. She explained that far-side quakes are intrinsically harder to detect because a large amount of energy is lost or diverted away as seismic waves travel through the planet. 

The two quakes occurred after InSight had been functioning on Mars for more than a full Martian year, which is equivalent to about two Earth years, and one of them was caused by a meteoroid impact. 

Another challenge in detecting the quakes was that they occurred in the "shadow zone". This is a part of Mars from which seismic waves tend to be refracted away from InSight, as a result of which it becomes very hard for a quake's echo to reach the lander unless the temblor is very large. However, with seismological expertise, scientists were able to analyse the seismic waves.

Composition of the Martian core

By detecting seismic waves that travel through a planet's core, scientists can refine their models of what the core looks like. The new study found that about a fifth of the Martian core is composed of elements such as sulphur, carbon, oxygen and hydrogen.