WASHINGTON: Mars is Earth’s next-door neighbour in the solar system — two rocky worlds with differences down to their very core, literally.

A new study based on seismic data obtained by Nasa’s robotic InSight lander is offering a fuller understanding of the Martian deep interior and fresh details about dissimilarities between Earth, the third planet from the sun, and Mars, the fourth.

The research, informed by the first detection of seismic waves travelling through the core of a planet other than Earth, showed that the innermost layer of Mars is slightly smaller and denser than previously known. It also provided the best assessment to date of the composition of the Martian core.

Both planets possess cores comprised primarily of liquid iron. But about 20 per cent of the Martian core is made up of elements lighter than iron — mostly sulphur, but also oxygen, carbon and a dash of hydrogen, the study found.

That is about double the percentage of such elements in Earth’s core, meaning the Martian core is considerably less dense than our planet’s core — though more dense than a 2021 estimate based on a different type of data from the now-retired InSight.

“The deepest regions of Earth and Mars have different compositions — likely a product both of the conditions and processes at work when the planets formed and of the material they are made from,” said seismologist Jessica Irving of the University of Bristol in England, lead author of the study published this week in the journal Proceedings of the National Academy of Sciences.

The study also refined the size of the Martian core, finding it has a diameter of about 3,560-3,620 km, approximately 20-50 km smaller than previously estimated. The Martian core makes up a slightly smaller percentage of the planet’s diameter than does Earth’s core.

The nature of the core can play a role in governing whether a rocky planet or moon could harbour life. The core, for instance, is instrumental in generating Earth’s magnetic field that shields the planet from harmful solar and cosmic particle radiation.

“On planets and moons like Earth, there are silicate — rocky — outer layers and an iron-dominated metallic core’’.

Published in Dawn, April 26th, 2023