Our Milky Way galaxy may hold giant terrestrial planets that contain up to 50 percent diamonds.

A new study suggests that some of the stars in the Milky Way could harbor diamond-made planets that are referred to as “carbon super-Earths.”

Researchers at Ohio State University recreated the temperatures and pressures of Earth’s lower mantle to study how diamonds form there and to understand what happens to carbon inside planets.

They also hoped to find whether solar systems that are rich in carbon could produce planets that are mostly made of diamonds, in which the study’s results suggested so.

Wendy Panero, associate professor in the School of Earth Sciences at Ohio State and Doctoral student Cayman Unterborn constructed computer models of the minerals that form in planets composed with more carbon than Earth using what they learned from the experiments.

The results suggest diamond-filled planets are possible.

“It’s possible for planets that are as big as fifteen times the mass of the Earth to be half made of diamond,” said Unterborn on Tuesday, where she was presenting the study at the American Geophysical Union meeting in San Francisco.

“Our results are striking, in that they suggest carbon-rich planets can form with a core and a mantle, just as Earth did,” Panero added.

“However, the cores would likely be very carbon-rich – much like steel – and the mantle would also be dominated by carbon, much in the form of diamond.”

Earth Suitable for Life, not Diamond Core

Earth does not have the chemical ingredients to make up a diamond rich planet, as Earth’s core is mostly iron and our mantle consist of mostly silica based minerals.

But what Earth does have is a hot interior, which results in geothermal energy, making our planet suitable for life.

The authors explained that diamonds transfer heat so quickly that a carbon super-Earth’s interior would quickly freeze causing there to be, no geothermal energy, no plate tectonics, and ultimately no magnetic field or atmosphere.

“We think a diamond planet must be a very cold, dark place,” Panero said.

Diamond-Rich Layer May Exist on Earth

Based on the data from the study, researchers using computer models of Earth’s interior verified what many geologist have long believed, that a diamond-rich layer is likely to exist in Earth’s lower mantle, just above the core.

However that region is far beneath the surface of the earth’s crust, extending to a depth of about 2,900 km.

Panero and former graduate Jason Kabbes concluded this by taking a tiny sample of iron, carbon, and oxygen to pressures of 65 gigapascals and temperatures of 2,400 Kelvin, the authors explained, close to 9.5 million pounds per square inch and 3,800 degrees Fahrenheit – conditions similar to the Earth’s deep interior.

The oxygen bonded with the iron, as they watched under the microscope, creating iron oxide, a type of rust, and leaving behind pockets of pure carbon, which became diamond.

The authors explained that this conclusion was not a surprise to them but when they “modeled what would happen when these results were applied to the composition of a carbon super-Earth, they found that the planet could become very large, with iron and carbon merged to form a kind of carbon steel in the core, and vast quantities of pure carbon in the mantle in the form of diamond.”

The researchers plan to do further research to see how different elements combined interact inside Earth.

"To date, more than five hundred planets have been discovered outside of our solar system, yet we know very little about their internal compositions,” said Unterborn, who is an astronomer by training.

“We’re looking at how volatile elements like hydrogen and carbon interact inside the Earth, because when they bond with oxygen, you get atmospheres, you get oceans – you get life,” Panero said. “The ultimate goal is to compile a suite of conditions that are necessary for an ocean to form on a planet.”