When Mars Cooled

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A crashing meteorite and data from a four-year-long NASA mission recently unveiled hot new details about Mars’ core, upending what scientists thought they knew about its fiery interior, Nature magazine reported.

It’s smaller and more complicated than they previously thought.

Between 2018 and 2022, NASA’s InSight mission observed and reported on the Red Planet’s seismic activities to learn more about its interior. But in September 2021, the agency’s craft detected seismic activity on Mars caused by a meteorite impact.

The impact struck on the side of the planet opposite InSight’s location, which allowed the probe to capture seismic energy traveling through the Martian core, reaching greater depths than previous “Marsquakes.”

In a new study, a research team used the data to uncover a layer of molten rock enveloping Mars’s liquid-metal core. This finding challenges previous assumptions about the planet’s interior: Scientists initially believed the planet’s core had a radius of nearly 1140 miles and contained high amounts of light chemicals, such as sulfur mixed with iron.

But the impact data showed that what was thought to be the boundary between the liquid core and the solid mantle is, in fact, the upper edge of a new molten rock layer. The core is beneath this molten layer and is smaller than previously thought, with a radius of approximately 1025 miles.

The adjusted core size has key implications for our understanding of Mars: It implies that the Martian core likely has fewer light elements, matching theoretical predictions. The discovery of a second liquid layer also aligns with other planetary observations.

Meanwhile, another study proposed that the molten rock layer may be a relic of an ancient magma ocean that once blanketed Mars. As this magma cooled and solidified, it left behind a deep layer of radioactive elements that still release heat, keeping the rock at the base of the mantle molten.

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