Mars should not have a solid inner core but it does, China-US study finds

By analysing seismic waves from marsquakes recorded by Nasa’s now-retired InSight lander, the team discovered a solid core about 600km (373 miles) in radius, or roughly 18 per cent of Mars’ radius, a similar proportion to Earth’s inner core.

The findings, published this week in Nature, helped to fill a major gap in our understanding of Mars’ deep interior, wrote Nicholas Schmerr, a planetary seismologist at the University of Maryland, College Park, in a commentary accompanying the paper.

This might also revive the long-debated idea that Earth was not the only planet to have once developed plate tectonics, said Ross Mitchell, a geologist at the Institute of Geology and Geophysics in Beijing, who was not involved in the research.

Inner cores form when the pressure is high enough and the temperature low enough for the liquid metal to “freeze” into a solid, Mitchell explained. Given enough time, any planet or moon will eventually form a solid inner core.

However, most bodies in the solar system have not cooled fast enough to form a solid inner core. “If this result holds, then it’s three of a kind: Earth, the moon and now Mars have inner cores,” he said.

South China Morning Post