The universe is stranger than you can imagine, and in the depths of space, there are wild and strange exoplanets to be found: planets with glowing rivers of lava, or planets under gravitational forces so strong they’re shaped like soccer balls. We can add to this list another kind of strange planet, those about which it rains diamonds.
The diamond rain effect is thought to occur deep within ice giants like Uranus and Neptune, and was recreated in a lab here on Earth in 2017. Now, researchers have found that this effect isn’t just a fluke. rare, but could be more common than previously thought.
To simulate this mix of chemicals, the researchers used a familiar material: PET plastic, the kind used in good packaging, which happens to be chemically similar to the conditions they wanted to create. ‘PET has a good balance between carbon, hydrogen and oxygen to simulate activity on ice planets,’ explained one of the researchers, Dominik Kraus from the University of Rostock.
The researchers used a high-powered laser to create shock waves in the plastic, then watched as the X-rays bounced off it. This allowed them to see how small diamonds were forming. The diamonds produced in the experiment were very small, called nanodiamonds, but much larger diamonds could form about 5,000 miles below the surface of an ice giant, where they would fall toward the planet’s icy core. The diamonds could even sink into the core and form a thick layer of diamonds.
In the new experiments, the team found that when they included oxygen, the nanodiamonds grew at lower temperatures and pressures, meaning having oxygen present makes the formation of diamond rain more likely. “The effect of oxygen was to speed up the splitting of carbon and hydrogen and thus encourage the formation of nanodiamonds,” Kraus said. “It meant that carbon atoms could combine more easily and form diamonds.”
With this discovery, the researchers now want to try the experiments again and include chemicals like ethanol, water and ammonia to even more closely model the ice giants’ environments.
“The fact that we can recreate these extreme conditions to see how these processes play out on very fast and very small scales is exciting,” said SLAC collaborator and scientist Nicholas Hartley. “Adding oxygen brings us closer than ever to seeing the full picture of these planetary processes, but there is still more work to be done. It’s a step on the way to getting the most realistic mix and seeing how these materials actually behave on other planets.”
The research is published in the journal Science Advances.