On Earth, diamonds are prized for their rarity (even though that may be changing), but on other planets they may appear as common as rocks. On ice giants like Uranus and Neptune, extreme pressure is thought to compress elements such as hydrogen and carbon, forming solid diamonds that rain down through the atmosphere.
The phenomenon has not been detected directly, but in 2017 a team of scientists reported that they had recreated the process in the laboratory. They did this by firing the world’s most powerful X-ray laser, the Linak Coherent Light Source (LCLS), at a sample of hydrocarbon material. This requires rapidly heating them to temperatures as high as 6,000°C (10,800°F) and generating powerful shock waves of several million atmospheres to form tiny “nanodiamonds.”
Although experiments have shown that this is technically possible, the team said that the original hydrocarbon materials such as polystyrene did not accurately model the elements present inside these cold planets, and oxygen is also present in abundance, so the researchers investigated other This key element can be introduced into mixed materials.
The researchers settled on PET, a plastic commonly used in food and beverage packaging, because it has a good balance between carbon, hydrogen and oxygen. The team repeated the experiment, scanning PET film samples with LCLS, and then using two different imaging techniques to examine on the one hand whether nanodiamonds formed, but also how fast and how large they were growing.
Ultimately, they detected a diamond density of 3.87 grams per cubic centimeter.
“The role of oxygen is to accelerate the splitting of carbon and hydrogen, thereby encouraging the formation of nanodiamonds,” said Dominik Kraus, author of the study. “This means that carbon atoms can combine more easily and form diamonds.”
Not only does the study provide a realistic basis for the diamond rain hypothesis on ice giants, but the team says it also demonstrates a new potential fabrication technique for these tiny diamonds that could be used in industrial abrasives, polishes, and perhaps It could also one day be used for highly sensitive quantum sensors.
The research was published in the journal Science Advances.