Getting a picture of where carbon was

This may look like something that belongs on an art gallery wall, but it is in fact related to a lab experiment designed to determine how carbon behaved during Earth’s violent formative period.

A team of US scientists from the Smithsonian, Harvard and Yale universities, and the Carnegie Institution for Science mimicked the Earth’s early core and compared carbon’s compatibility of silicates that comprise the Earth’s mantle (outer circle) to its compatibility with the iron that comprises the planet’s core (inner circle). 

“We found that more carbon would have stayed in the mantle than we previously suspected,” says Elizabeth Cottrell, the Smithsonian’s National Museum of Natural History curator of rocks and ores.

“This means the core must contain significant amounts of other lighter elements, such as silicon or oxygen, both of which become more attracted to iron at high temperatures.”

Despite these findings – which are reported in a paper in the Proceedings of the National Academy of Sciences – the vast majority of Earth’s total carbon inventory does likely exist down in the core, the researchers say. And it only makes up a negligible fraction of the core’s overall composition.

Cottrell and colleagues hope their work will help scientists understand how much carbon likely exists in the planet’s core and the ways it influences chemical and dynamic activities that shape the world, including the convective motion that powers the magnetic field that protects Earth from cosmic radiation.