Data from a meteorite impact on Mars, which she recorded in 2021 NASA probe InSightare now helping to clear up some confusion about the interior composition this planet. A pair of studies published in the journal Nature independently reported that the iron-rich core of Mars is smaller and denser than previous measurements suggestedand is surrounded by molten rock.

The now defunct InSight probe, which arrived on Mars in November 2018, four years recorded seismic waves arising from earthquakes on Mars. Thanks to it, scientists had a better understanding of what is happening under the surface of the planet. Martian core estimates based on InSight’s first earthquake data, however they didn’t quite fit. Scientists then discovered that the radius of the core is somewhere between 1118 and 1149 kilometers, so it is much larger than expectedand that contains an unexpectedly high percentage of lighter elements supplementing heavy liquid iron.

Calculation of the percentage of the content of these light elements at the same time bordered on the impossible, as reported by Dongyang Huang of ETH Zurich, co-author of one of the studies. “We have been thinking about this result ever since,” he added. Then came the breakthrough when in September 2021, a meteorite hit Mars. And this on the other side of the planet than where the InSight probe is located, and created seismic waves that, according to ETH Zurich PhD student Cecilie Duran made it possible to understand the composition of the nucleus.

Based on these measurements, both teams found that the core of Mars has rather radius about 1013–1060 km. That, the ETH Zurich team notes, is about half the radius of Mars itself. A smaller core would also be denser, meaning that previously unexplained abundances of light elements may actually exist in smaller, more reasonable quantities. The core is after that surrounded by a layer of molten silicates about 90 kilometers thick, which distorted the original estimates. Moreover, it is unlike anything found in the Earth’s interior.

According to Vedran Lekic of the University of Maryland, co-author of the second paper, this layer serves as a kind of a “heating blanket” for the core that concentrates radioactive elements. Its study could help scientists uncover answers to questions about the formation of Mars and its absence of an active magnetic field.