‘Diamond Rain’ on Giant Ice Planets May Be More Common Than Thought

Using a method called X-ray diffraction, they watched the material’s atoms rearrange themselves into small diamond-like regions. They simultaneously used another method called small-angle scattering, which had not been used in the first paper, to measure the speed and size of these regions. Using this additional method, they were able to determine that these diamond regions were up to a few nanometers wide. They found that with the presence of oxygen in the material, nanodiamonds could grow at lower pressures and temperatures than previously observed.

“The effect of the oxygen was to accelerate the separation of carbon and hydrogen and thus encourage the formation of nanodiamonds,” Kraus said. “This meant that carbon atoms could combine more easily and form diamonds.”

icy planets

The researchers predict that the diamonds on Neptune and Uranus would become much larger than the nanodiamonds produced in these experiments – possibly millions of carats in weight. For thousands of years, diamonds could slowly trickle through the planets’ ice sheets and come together in a thick layer of bling around the solid planetary core.

The team also found evidence that, in combination with the diamonds, superionic water could also form. This newly discovered phase of water, often described as “hot black ice”, exists at extremely high temperatures and pressures. Under these extreme conditions, the water molecules separate and the oxygen atoms form a crystal lattice in which the hydrogen nuclei float freely. Because these floating nuclei are electrically charged, superionic water can conduct electric current and could explain the unusual magnetic fields on Uranus and Neptune.

The findings could also impact our understanding of planets in distant galaxies, since scientists now believe ice giants are the most common form of planet outside our solar system.

“We know that the Earth’s core is mainly composed of iron, but many experiments are still investigating how the presence of lighter elements can alter the melting and phase transition conditions,” said SLAC scientist and collaborator Silvia Pandolfi. . “Our experiment demonstrates how these elements can alter the conditions under which diamonds form on ice giants. If we want to accurately model the planets, we need to get as close as possible to the actual composition of the planetary interior.

rough diamonds

The research also points to a potential way forward for the production of nanodiamonds by laser shock compression of inexpensive PET plastics. Although they are already included in abrasives and polishing agents, in the future these tiny gemstones could potentially be used for quantum sensors, medical contrast agents and reaction accelerators for renewable energy.

“The way nanodiamonds are currently made is to take a bunch of carbon or diamond and detonate it with explosives,” said SLAC scientist and collaborator Benjamin Ofori-Okai. “It creates nanodiamonds of different sizes and shapes and is difficult to control. What we see in this experiment is a different reactivity of the same species under high temperature and pressure. In some cases, diamonds seem to form faster than others, suggesting that the presence of these other chemicals may speed up this process. Laser production could offer a cleaner and more easily controlled method of producing nanodiamonds. If we can devise ways to change some things about responsiveness, we can change how quickly they form and therefore how big they are.

Next, the researchers plan similar experiments using liquid samples containing ethanol, water and ammonia – which Uranus and Neptune are mostly made up of – which will bring them even closer to understanding exactly how Earth formed. the rain of diamonds on other planets.

“The fact that we can recreate these extreme conditions to see how these processes happen on a very small scale and very quickly is exciting,” said SLAC scientist and collaborator Nicholas Hartley. “Adding oxygen brings us closer than ever to the full picture of these planetary processes, but there is still work to be done. It’s a step on the road to getting the most realistic mix and seeing how these materials really behave on other planets.

The research was supported by the DOE’s Office of Science and the National Nuclear Security Administration. LCLS is a user facility of the DOE Office of Science.

Portions of this article were adapted from a press release written by the Helmholtz-Zentrum Dresden-Rossendorf.


Quote: Zhiyu He et al., Scientists progressSeptember 2, 2022 (10.1126/sciadv.abo0617)

Contact details of the press office: Manuel Gnida, [email protected]


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