Earth's Fiery Depths Filled with Brimstone

Earth’s inner core is a metallic mix of iron and light elements such as sulfur, hydrogen and silicon, a new study finds.

This isn’t the first time scientists have proposed that Earth’s fiery depths are filled with brimstone, another name for sulfur. That’s because the inner core is less dense than it would be if the solid metal ball were pure iron. However, the new research further confirms the idea with tests of pure iron at the extreme temperatures and pressures found in the inner core.

Researchers at Tohoku University in Sendai, Japan, mimicked the inner core in a laboratory equipped with a laser-heated diamond anvil cell. A small crumb of pure iron was squeezed between two diamond-tipped anvils to create high pressure and blasted with laser beams to boost the temperature. The experiment reached 163 gigapascals (about 1.6 million times the pressure at sea level) and about 5,000 degrees Fahrenheit (3,000 kelvins, or about 2,700 degrees Celsius).

During the experiment, the team measured how fast sound waves traveled through iron at these conditions. If the Earth’s inner core was pure iron, then the speed of sound waves traveling through the core should be similar to the experimental results.

But instead, the researchers discovered the velocity of sound waves through Earth’s actual core is lower than if it were made only of iron. The data and observations match more closely if 5 to 10 percent of the core’s weight is a mix of sulfur, hydrogen and silicon, the researchers reported in the journal Science Advances.

“This result helps us constrain the candidate elements in the core,” said lead study author Tatsuya Sakamaki, of Tohoku University. “We already know that the Earth’s core contains some amount of light elements because the density of the core is smaller than that of iron. In this study, we newly show that the velocity of the core is also smaller than that of iron,” Sakamaki told Live Science in an email interview.

Read more at Discovery News