Iron 'Snow' Rains Down on Earth's Core, Scientists Discover

Deep inside the earth, iron "snow" is falling from the bottom of the planet's molten outer core onto the top of the inner core, research suggests.

The tiny crystals of iron have formed piles on top of the inner core which measure up to 200 miles thick in some places, according to a study published in the journal JGR Solid Earth.

Scientists can't observe the core of the earth directly, so to understand this region they analyze seismic waves which travel through the planet.

However, there are discrepancies between seismic data which has been collected recently and current models of the earth core. Namely, the waves move slower than expected through the base of the outer core and faster than expected through the top of the inner core in the eastern hemisphere.

In order to explain this, the authors of the paper suggest that around 15 percent of the lower outer core is made from iron-based crystals which fall down and pile up on top of the solid inner core.

"It's sort of a bizarre thing to think about," Nick Dygert, an author of the study from the University of Tennessee, said in a statement. "You have crystals within the outer core snowing down onto the inner core over a distance of several hundred kilometers."

According to the study, this layer of iron crystals can explain the seismic data discrepancies. For example, the crystal layer is thinner in the eastern hemisphere, which could be a reason why the seismic waves move faster here.

"The inner-core boundary is not a simple and smooth surface, which may affect the thermal conduction and the convections of the core," Youjun Zhang, lead author of the study from Sichuan University in China, said in a statement.

Earth, iron snow, inner core
A simplified graphic of the inner earth as described by the new research. The white and black layers represent a slurry layer containing iron crystals. The iron crystals form in the slurry layer of the outer core (white.) These crystals “snow” down to the inner core, where they accumulate and compact into a layer on top of it (black.) The compacted layer is thicker on the western hemisphere of the inner core (W) than on the eastern hemisphere (E.) UT Austin/Jackson School of Geosciences

The scientists say the latest findings could have implications for our understanding of several geological processes because the core is responsible for phenomena that affect the whole planet. For example, it drives the movement of tectonic plates and generates the earth's magnetic field.

Bruce Buffet, a geoscientist from the University of California, Berkeley, who was not involved in the study, said the research could shed light on the formation of the earth's core.

"Relating the model predictions to the anomalous observations allows us to draw inferences about the possible compositions of the liquid core and maybe connect this information to the conditions that prevailed at the time the planet was formed," Buffet said. "The starting condition is an important factor in Earth becoming the planet we know."

The earth is made up of several layers, beginning with the crust on the exterior, followed by the mantle, outer core and inner core—which is located in the center of the planet.