Scientists upend understanding of Mars’ core size

Mars’ core is smaller and denser than previously thought, according to a team of international scientists.

The researchers have used data from the NASA InSight lander to deduce that Mars’ liquid iron core is surrounded by a 150km layer of molten silicate.

Previous data from the InSight lander (which is fitted with a seismograph) suggested that the core was large but not dense, with lots of light elements like sulphur, carbon and oxygen.

But this research has used new data to draw a more precise picture, concluding that the core is smaller and denser.

The researchers have published their findings in two Nature papers.

They analysed marsquakes recorded by the lander, to make deductions about how the quakes had travelled through the planet’s interior.

This allowed them to conclude that what was previously thought of as the edge of Mars’ core was actually a layer of silicate. The real core, underneath, was smaller and denser.

Their new core size is 1,650 ± 20km in radius, as opposed to the previous estimate of 1,800km.

The silicate layer could explain why Mars doesn’t currently have a magnetic field. It insulates the core and stops it from cooling, which in turn stops it from creating a “thermal dynamo” which causes a magnetic field.

Mars has had a magnetic field in the past, but the researchers say “alternative external sources” like asteroid impacts and satellite orbits may have created it.