Scientists identify molten layer deep within interior of Mars

Seismic waves generated by a meteorite impact on the other side of Mars from where NASA’s InSight lander sits have provided new clues about the Red Planet’s deep interior

Seismic waves generated by a meteorite impact on the other side of Mars from where NASA's InSight lander sits have provided new clues about the Red Planet's deep interior, prompting scientists to reappraise the anatomy of Earth's planetary neighbour.

The new seismic data indicates the presence of a hitherto unknown layer of molten rock surrounding a liquid metallic core - the planet's innermost component - that is smaller and denser than previously estimated, researchers said on Wednesday.

Waves generated by quakes - including those caused by meteorite impacts - vary in speed and shape when journeying through different materials inside a planet. Data from InSight's seismometer instrument has enabled the planet's internal structure to come into focus.

The meteorite impact that occurred in a Martian highland region called Tempe Terra on Sept. 18, 2021, triggered a magnitude 4.2 quake and left a crater about 425 feet (130 meters) wide. It occurred on the opposite side of Mars from InSight's location in a plains region called Elysium Planitia.

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"The importance of the far side impact was to produce seismic waves that traversed the deep interior of the planet, including the core. Previously, we had not observed any seismic waves that had transited the core. We had only seen reflections from the top of the core," said planetary scientist Amir Khan of ETH Zürich in Switzerland, lead author of one of two scientific papers on the new findings published in the journal Nature.

The behaviour of the waves indicated that previous assessments of the Martian interior were missing something - the presence of a molten silicate layer about 90 miles (150 km) thick surrounding the core. This molten region sits at the bottom of the interior portion of the planet called the mantle.