“In a discovery that challenges long-held beliefs, scientists from China and the U.S. have found direct evidence of a solid inner core inside Mars. If confirmed, it would mean that Earth, the Moon, and Mars all share the same inner structure,” notes a historian.
As a newspaper explains:
Scientists in China and the United States have found the first direct evidence of a solid inner core inside Mars – a structure long thought not to exist – challenging prevailing theories about how the red planet formed and cooled. By analyzing seismic waves from marsquakes, the team discovered a solid core about 373 miles in radius, or roughly 18 per cent of Mars’ radius, a similar proportion to Earth’s inner core….This might also revive the long-debated idea that Earth was not the only planet to have once developed plate tectonics…Inner cores form when the pressure is high enough and the temperature low enough for the liquid metal to “freeze” into a solid…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.”…
On Earth, plate tectonics played a key role in that rapid cooling. The movement of surface plates helped carry heat from deep inside the planet to the surface – like vents letting steam escape. Mars, on the other hand, is believed to have a molten layer between its mantle and core that should have acted like a blanket, slowing its cooling. “If Mars had plate tectonics in the past, that could have helped it cool rapidly despite the insulation.”…Stanford geophysicist Norman Sleep argued that Mars might have once had plate tectonics, although those plates were no longer active.
