Mars has a surprise layer of molten rock inside

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https://www.nature.com/articles/d41586-023-03271-4

By Alexandra Witze, Nature. 

Excerpt: A meteorite that slammed into Mars in September 2021 has rewritten what scientists know about the planet’s interior. By analysing the seismic energy that vibrated through the planet after the impact, researchers have discovered a layer of molten rock that envelops Mars’s liquid-metal core. The finding, reported today in two papers in Nature1,2, means that the Martian core is smaller than previously thought. It also resolves some lingering questions about how the red planet formed and evolved over billions of years. The discovery comes from NASA’s InSight mission, which landed a craft with a seismometer on Mars’s surface. Between 2018 and 2022, that instrument detected hundreds of ‘marsquakes’ shaking the planet. Seismic waves produced by quakes or impacts can slow down or speed up depending on what types of material they are travelling through, so seismologists can measure the waves’ passage to deduce what the interior of a planet looks like. ...the September 2021 meteorite impact “unlocked everything”, says Henri Samuel, a geophysicist at the Institute of Earth Physics of Paris and lead author of one of today’s papers1. The meteorite struck the planet on the side opposite to where InSight was located. That’s much more distant than the marsquakes that InSight had previously studied, and allowed the probe to detect seismic energy travelling all the way through the Martian core4.... For

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