Marsquakes indicate a solid core for the red planet, just like Earth

By: Marcia Dunn, The Associated Press Posted: 10:04 AM CDT Wednesday, Sep. 3, 2025 Last Modified: 6:25 PM CDT Wednesday, Sep. 3, 2025

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CAPE CANAVERAL, Fla. (AP) — Scientists revealed Wednesday that Mars’ innermost core appears to be a solid hunk of metal just like Earth’s.

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CAPE CANAVERAL, Fla. (AP) — Scientists revealed Wednesday that Mars’ innermost core appears to be a solid hunk of metal just like Earth’s.

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CAPE CANAVERAL, Fla. (AP) — Scientists revealed Wednesday that Mars’ innermost core appears to be a solid hunk of metal just like Earth’s.

The Chinese-led research team based their findings on seismic readings from NASA’s InSight lander on Mars, which recorded more than 1,300 marsquakes before shutting down in 2022. The spacecraft landed on a broad plain near Mars’ equator in 2018.

Previous studies pointed to liquid at the heart of the red planet. The latest findings indicate the inner core, while small, is indeed solid and surrounded by molten metal — a liquid outer core.

This image provided by the European Space Agency and taken with the ESA's High Resolution Stereo Camera (HRSC) aboard the Mars Express spacecraft shows Mars as the spacecraft approaches the planet from a distance of 5.5 million kilometers.

The Martian inner core extends from the planet’s center out to a radius of approximately 380 miles (613 kilometers), according to the scientists whose findings appeared in the journal Nature.

It’s likely composed of iron and nickel, the same ingredients as Earth’s core, but quite possibly also enriched with lighter elements like oxygen.

Mars’ liquid outer core is bigger, stretching from 380 miles (613 kilometers) to as much as 1,100 miles (1,800 kilometers) from the planet’s center.

Crystallization of Mars’ inner core may have occurred in the past and still be occurring today, one of the lead investigators, Daoyuan Sun of the University of Science and Technology of China, said in an email.

Mars’ core initially would have been entirely liquid. It’s unclear whether the liquid outer core contains any solid material like droplets or whether there might be “a mushy zone” near the boundary between the inner and outer cores, he added.

For their study, Sun and his team relied primarily on 23 marsquakes recorded by InSight, all of them relatively weak. The epicenters were 740 miles to 1,465 miles (1,200 kilometers to 2,360 kilometers) away from the lander.

“Our results suggest that Mars has a solid inner core making up about one-fifth of the planet’s radius — roughly the same proportion as Earth’s inner core. However, this similarity may be just coincidental,” Sun said.

While praising the results, the University of Maryland’s Nicholas Schmerr, who was not involved in the study, said questions regarding Mars’ core are far from settled. With InSight out of action, there will be no new recordings of marsquakes to further reveal the red planet’s insides, he noted.

“There are a lot of details about the exact shape of the inner core and composition of the inner and outer core of Mars that will require a network of InSight like seismometer stations to resolve,” Schmerr said in an email.

More detailed modeling is necessary to develop a clearer picture of how the inner core formed and “what it reveals about the history of Mars’ magnetic field,” said Sun.

At present, Mars lacks a magnetic field, possibly because of the slow crystallization of the planet’s solid core, Schmerr added.

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