Researchers say a surprise layer of molten rock envelops Mars' liquid-metal core

Scientists have said in new studies that the core of Mars can look bigger than it actually is because of a previously unknown layer of molten rock which is surrounding it.

The researchers have said that the pair of studies may finally solve a mystery from two years ago about how the centre of Mars appeared surprisingly large and soft.

To carry out the study, the team of scientists analysed seismic waves on the planet by using sensors on NASA's InSight lander, which touched down on the Red Planet in 2018.

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The researchers hoped to find insights into the planet's inner structure by studying the seismic waves that rippled through Martian rock after a meteorite slammed into Mars in September 2021.

The findings were reported on Thursday (Oct 26) in two papers in Nature Journal. It mentioned that the researchers have discovered a layer of molten rock that envelops Mars's liquid-metal core.

In the report, Nature mentioned that the seismic waves which are produced by quakes or impacts can slow down or speed up depending on what typeof material they are travelling through.

Hence, seismologists can measure the waves' passage in order to understand the details of the interior of a planet and what it looks like.

Researchers used the same technique on Earth as they probed the earthquakes to discover the planet's layers which are: a brittle outer crust, a mostly solid mantle, a liquid outer core, and a solid inner core.

Ever since its landing on the Red Planet, InSight's seismometer has recorded many observations of Mars-quake, in fact, it was also the first to detect marsquakes.

On the basis of the mission's observations of quakes in July 2021, researchers established the fact that the liquid core of Mars seemed to have a radius of around 1,830 kilometres, which was bigger than many scientists were expecting.

The finding also suggested that the core has surprisingly high amounts of light chemical elements, such as sulfur, mixed with iron.

But Henri Samuel, who is a geophysicist at the Institute of Earth Physics of Paris and lead author of one of the papers, said that the September 2021 meteorite impact "unlocked everything".

"A second liquid layer inside the planet also meshes better with other evidence, such as how Mars responds to being deformed by the gravitational tug of its moon Phobos," Nature had written.

In another paper, the same conclusions were made as the team, independent of Samuel's, agreed that Mars'core is surrounded by a layer of molten rock. However, they estimated that the core has a radius of 1,675 kilometres.

Its lead author, Amir Khan, who is a geophysicist at ETH Zurich, said that having molten rock right up against molten iron "appears to be unique".

"You have this peculiarity of liquid–liquid layering, which is something that doesn't exist on Earth," he added.