Mars Insight Mission Finds Evidence for a Molten Layer Covering the Martian Core

Rebecca Jean T.
4 min readMar 6, 2024

While geologists have been studying our own planet’s interior using seismic waves for over a century, it has only been over the past few decades that we’ve developed the technology to be able to do so on other worlds. A recent look at seismic data from a meteorite impact provides information about a newly discovered layer of molten rock surrounding the Martian core.

Mars’ red and brown surface. A large crack is in the middle of the image, running horizontal across the planet. Other surface features include darker regions in the bottom right, and two large circular volcanoes in the upper left.
A mosaic of 102 images taken by the Viking Orbiter in 2013. Mars’ large canyon system, Valles Marineris, takes center stage in the middle of the image. Credit: NASA/JPL-Caltech.

A Liquid Layer Around the Martian Core

The earliest detection of Mars’ liquid core dates all the way back to 2003, when scientists using radio data from the Mars Global Surveyor spacecraft found that Mars has either a completely liquid core that had not completely cooled or a liquid outer core with a solid inner core. More recent data from the Mars InSight lander from a set of studies published in 2021 in suggested that this core was much larger than expected, a whopping 2,235 miles in diameter, or about half the size of the planet itself.

Concept art of NASA’s InSight lander on the surface of Mars deploying its instruments. Credit: NASA/JPL-Caltech.

InSight, short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, was a lander mission aimed at understanding Mars’ interior conditions using seismic waves. On Earth, we have been able to study the layers of our own planet’s interior using seismic waves from earthquakes. As seismic waves pass through different layers of the Earth they change direction and speed, which can be used to determine the sizes and composition of each layer. InSight’s detections of seismic waves on Mars ended in late 2022, but planetary scientists are still combing through the data and learning more about the Martian interior every day.

Most recently, two studies published in Nature in October 2023 provide new evidence that Mars’ core is not as large as the 2021 studies suggest ( 1)( 2). Instead, the Martian core appeared to be larger because of a layer of molten rock surrounding the core, which caused it to appear bigger than it actually was. Researchers were able to determine this with seismic waves detected after the 2021 studies were published. These seismic waves, caused by a meteorite impact, penetrated the core…

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Rebecca Jean T.

Published author on NASA’s Radio Jove project. Researching science topics to deliver to you in bite-sized stories.