A study has found that “diamond rain,” a strange type of rain on icy giant planets, may be more common than previously thought.
In a previous experiment, researchers mimicked the extreme temperatures and pressures found deep within the ice giants Neptune and Uranus, and for the first time, they observed diamond precipitation as they formed.
Investigate this process in a new material very similar to the chemical structure of Neptune and UranusScientists from the Department of Energy’s SLAC National Accelerator Laboratory and their colleagues have discovered that the presence of oxygen is made by diamond formation Most likely, allowing them to form and grow in a wider range of conditions and across more planets.
The new study provides a more complete picture of how diamond rain forms on other planets, and here on Earth, could lead to a new method for manufacturing nanodiamonds, which has a very wide range of applications in drug delivery, medical sensors, non-invasive surgery, sustainable manufacturing and electronics. Quantum.
“The previous paper was the first time we had directly seen diamond formation from any alloys,” says Siegfried Glenzer, director of the High Energy Density Division at SLAC. “Since then, there’s been a lot of experimenting with different pure substances. But inside planets, it’s more complicated; there are a lot of chemicals in the mix. And so, what we wanted to find out here is what kind of effect these additional chemicals have.”
The team, led by Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the University of Rostock in Germany, as well as the French Polytechnic School in collaboration with SLAC, reported the results in science progress.
From plastic to “diamond rain”
In the previous experiment, the researchers studied a plastic made of a mixture of hydrogen and carbon, which are essential components of the overall chemical makeup of Neptune and Uranus. But in addition to carbon and hydrogen, ice giants contain other elements, such as large amounts of oxygen.
In the most recent experiment, the researchers used polyethylene terephthalate plastic — often used in food packaging, plastic bottles and containers — to more accurately reproduce the composition of these planets.
“PET has a good balance of carbon, hydrogen and oxygen to simulate activity in icy planets,” says Dominic Krause, a physicist at HZDR and a professor at the University of Rostock.
The researchers used a high-powered optical laser in the Matter in Extreme (MEC) instrument at SLAC’s Linac Coherent Light Source (LCLS) to create shock waves in PET. Next, they investigated what happened in the plastic using X-ray pulses from the LCLS.
Using a method called X-ray diffraction, they watched the material’s atoms rearranged in tiny diamond regions. They simultaneously used another method called small angle scattering, which was not used in the first paper, to measure how fast and large these regions are. Using this additional method, they were able to determine that these diamond regions had grown to even a few nanometers wide. They found that with oxygen in the material, nanodiamonds were able to grow at lower pressures and temperatures than previously observed.
“The effect of the oxygen was to speed up the splitting of carbon and hydrogen and thus encourage the formation of nanodiamonds,” Krause says. “This means that the carbon atoms can combine more easily and form diamonds.”
Neptune and Uranus
The researchers predict that the diamonds on Neptune and Uranus will become much larger than the nanodiamonds produced in these experiments – perhaps weighing millions of carats. Over thousands of years, diamonds may slowly sink through the planets’ icy layers and collect in a thick layer of luster around the planet’s solid core.
The team also found evidence that, in combination with diamond, ionic superwater may also form. This newly discovered phase of water, often described as “hot black ice,” exists at extremely high temperatures and pressures. In these extreme conditions, water molecules disintegrate and oxygen atoms form a crystal lattice in which hydrogen nuclei float freely. Because these free-floating cores are electrically charged, super-ionic water can conduct electric current and can explain the unusual magnetic fields in Uranus and Neptune.
The findings could also affect our understanding of planets in distant galaxies, as scientists now believe ice giants are the most common form of planets outside our solar system.
“We know that the Earth’s core is made mostly of iron, but many experiments are still looking at how having lighter elements can alter their melting conditions and phase transitions,” says SLAC scientist and collaborator Silvia Pandolfi. Our experiment shows how these elements can alter the conditions in 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 inner planets.”
nano diamond making
The research also points to a potential forward path for nanodiamond production via laser-driven shock compression of cheap PET plastics. While they are already included in abrasives and polishing agents, in the future, these tiny gems could be used in 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 diamonds and blast them with explosives,” says SLAC scientist and collaborator Benjamin Ofori Okai. “This results in nanodiamonds of different sizes and shapes that are difficult to control. What we see in this experiment is a different reaction of the same species under high temperature and pressure.
“In some cases, diamonds appear to form faster than others, indicating that the presence of these other chemicals can speed up this process. Laser production could provide a much cleaner and more easily controlled method for producing nanodiamonds. If we can design methods for To change some of the things about the reaction, we can change how quickly they form and therefore their size.”
Next, the researchers plan similar experiments using liquid samples containing ethanol, water and ammonia – which are often what Uranus and Neptune are made of – which will bring them closer to understanding how diamond rain forms on other planets.
“The fact that we can recreate these extreme conditions to see how these processes operate at very fast and very small scales is exciting,” says SLAC scientist and collaborator 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 is a step on the way towards getting the most realistic mixture and seeing how these materials really behave on other planets.”
The research received support from the Department of Energy’s Office of Science and the National Nuclear Security Administration. LCLS is a user facility of the Department of Energy’s Office of Science.