Diamond rain can drip from huge ice planets

Experiments on Earth show an abundance of diamonds literally raining down on ice giant planets like Neptune and Uranus, and may even point to a new way to produce tiny nanodiamonds for use on our planet.

Earlier research suggested that actual diamonds may be present in rain and hail in the atmospheres of giant planets. including Saturnbut a new international collaboration finds that diamond rain may be relatively common throughout the galaxy.

Researchers from Germany, France and the US modified previous experiments using a new material that more closely resembles the chemistry found in the ice giants. It turns out that this mysterious material is not exotic at all, but a type of PET plastic that is commonly used in bottles that you can buy in the store. The more representative chemical mixture in the plastic basically added levels of oxygen that were not present in the earlier experiments.

Using the plastic as a proxy for the chemistry of an ice giant’s atmosphere, they then sealed it with a laser to simulate the atmospheric pressure present on such planets to see what would happen.

“The effect of oxygen was to accelerate the separation of carbon and hydrogen and thus promote the formation of nanodiamonds.” Dominik Kraus, a physicist and professor at Germany’s Rostock University, said in a statement. “This means that carbon atoms can combine more easily to form diamonds.”

In other words, the actual environment of the ice gas giant planets has more oxygen, and more oxygen means more diamonds.

The team, which included researchers from France’s École Polytechnique in collaboration with the SLAC National Accelerator Lab in Silicon Valley, published their study in the journal Scientific progress in Friday.

Remarkably, scientists say that diamonds produced by conditions on Neptune or Uranus can weigh millions of carats. The record for a diamond on Earth is just over 3,100 carats. There may even be a thick diamond layer somewhere above the planets’ cores.

It will be a long time before it is possible to search for mega diamonds on other planets, but the research could provide insight into new ways to produce nanodiamonds. Such miniature gems are already used in some varnishes, but could be used in sensors and renewable energy technologies.

“The way nanodiamonds are currently made is by taking a bunch of carbon or diamond and blowing it up with explosives,” said scientist and SLAC Fellow Benjamin Ofori-Okai. “Laser fabrication may offer a cleaner and more easily controlled method of producing nanodiamonds.”

The researchers are planning more experiments that will again change the chemistry involved to get an even more accurate picture of how diamond rain forms and the processes that can create the gems from thin (or dense) air.