Deep under the dusty red surface of Mars burns a core of liquid iron – and it’s very different to what scientists previously thought.
Firstly, as a new study published in Nature outlines, the core is much smaller than past estimates. The centre of Mars is also much denser, with the core surrounded by a molten silicate layer – essentially, a mixture of rocks in hot, liquid form.
NASA gathered the measurements for these calculations using its InSight lander’s seismometer during a mission in 2021 known as the Seismic Experiment for Interior Structure (SEIS). The dome-shaped instrument sat on Mars’s surface and measured the seismic vibrations, or the planet’s ‘pulse’, which hint at its internal activity.
These measurements initially indicated that the core is large but with a low density, composed of liquid iron alongside lighter elements like sulphur, carbon, oxygen and hydrogen.
However, this theory didn’t match up with existing scientific estimates of the quantities of these elements available on Mars. So the scientists tried something else.
How was the discovery made?
First, two independent teams of scientists analysed recent seismic signals from Mars. They then made simulations and geophysical models to produce new estimates for the size of Mars’s core – and what it’s made of.
Instead of a large core, both teams found that its smaller, liquid iron core is actually surrounded by around 150km (93 miles) of soft, molten rock. Being much smaller, the core likely has a denser composition of elements.
How important is the discovery?
Space geologist Prof Suzan Van der Lee of Northwestern University, USA – who was not directly involved in the study – called these “the most accurate and precise estimates so far of Mars’s core and mantle structure.”
She added: “Their findings improve our understanding of the layers of Mars that lie deep beneath the crust, and help to put the structure and origins of the Martian interior into context with formation and evolution scenarios for rocky (terrestrial) planets in the Solar System.”
Despite the recent breakthrough, scientists aren't sure about how dense the soft layer surrounding the core is – or what it's made from. As Van der Lee points out, astronomers will need to do further research to align the findings and learn even more about the Red Planet.
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