Scientists make it rain diamonds to help us better understand icy planets

22 Aug 2017

Image: Blue Vista Design/Shutterstock

Diamond rain might sound like the name of a pop single, but scientists have managed to create the real thing in a fascinating experiment.

On distant icy planets and moons, diamond rain is a regular occurrence due to the extremely high pressure of an atmosphere that squeezes hydrogen and carbon found in the interior of these planets to form solid diamonds.

Then, over millions of years, this glittering precipitation slowly sinks down into the interior.

Future Human

At least, that has been the theory of astrophysicists for some time now, but now one team of researchers has proven it once and for all by recreating the phenomenon in a high-pressure chamber.

The hypothesis had suggested that this diamond rain forms 8,000km beneath the surface of Uranus and Neptune, as these planets typically contain solid cores surrounded by a dense slush of different ices, made up of many common elements.

In a paper published to the journal Nature Astronomy, the team detailed how it simulated the environment found inside these planets by creating shock waves in plastic with an intense optical laser, using the Matter in Extreme Conditions instrument at the SLAC National Accelerator Laboratory in the US.

The plastic – in this case, polystyrene – simulates compounds formed from methane, with just one carbon bound to four hydrogen atoms, creating the distinct blue cast of Neptune.

During experiments, the team was able to see that nearly every carbon atom of the original plastic was incorporated into small diamond structures just a few nanometres wide.

On Uranus or Neptune, however, these crystals would be significantly larger – so much so that the team predicted they could be millions of carats in weight, gathering around the planets’ core and forming thick layers of glittering diamonds.

‘One of the best moments of my scientific career’

“Previously, researchers could only assume that the diamonds had formed,” said Dominik Kraus, lead author of the paper. “When I saw the results of this latest experiment, it was one of the best moments of my scientific career.”

This wasn’t the first time that diamond rain had been created in the lab, but it was the first time that it could be measured using the lab’s high-energy optical lasers, not to mention that the experiment created much purer samples than ever before.

From an astronomical perspective, this breakthrough is hugely important as, by seeing how elements mix and clump together, scientists can calculate the relationship between the mass and radius of planets, allowing for better modelling and classification processes.

“We can’t go inside the planets and look at them, so these laboratory experiments complement satellite and telescope observations,” Kraus said.

The nano-diamonds also potentially have a multitude of different uses here on Earth, in the fields of medicine, scientific equipment and electronics.

Colm Gorey was a senior journalist with Silicon Republic