A bizarre form of precipitation known as “diamond rain” — long thought to occur deep within ice giants — may be more common than previously thought.
A team of researchers experimented with materials similar to those found in ice giants like the solar system planets Neptune and Uranus, and found that the presence of oxygen increases the likelihood of diamond formation, and that diamonds can form at low temperatures and low pressures.
This means that diamonds can grow in a variety of conditions in these cold worlds. Therefore, this would make it more likely that the diamond rain would pass through the interior of the ice giant.
related: Yes, Uranus and Neptune Really Have ‘Diamond Rain’
The same experiment also uncovered the formation of a bizarre form of water that could help explain the magnetic fields of Uranus and Neptune that have so far puzzled astronomers.
The research could change how we think about ice giants, which some scientists consider to be one of the most common forms of exoplanets — planets outside our solar system.
The team of scientists, including researchers from the U.S. Department of Energy’s SLAC National Accelerator Laboratory and the Helmholtz Center Dresden-Rossendorf (HZDR) and the University of Rostock, built on previous studies of conditions and materials inside ice giants , observed the formation of diamond rain.
New research predicts that diamonds on Neptune and Uranus could grow to large sizes and could weigh millions of carats.
Ice giants lack a solid surface, but become denser toward the core, meaning diamonds could sink into the ice over thousands of years. They will begin to gather around the planet’s solid heart, forming a thick layer of diamond.
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In addition, the team found that a new water phase called superionic water, sometimes referred to as “hot black ice,” formed next to the diamond.
Superionized water exists at high temperature and pressure, in which water molecules and oxygen components decompose to form a lattice, and hydrogen nuclei float freely in the lattice.
Hydrogen nuclei are positively charged, which means superionized water can conduct an electric current, which creates a magnetic field. This could explain the unusual magnetic fields seen around Uranus and Neptune.
“Our experiments show how these elements can change the conditions under which diamonds form on ice giants,” SLAC scientist and team member Silvia Pandolfi said in a statement. (opens in new tab) “If we want to accurately model planets, then we need to get as close as possible to the actual composition of the planet’s interior.”
More complex diagram of diamond formation
Siegfried Glenzer, director of the High Energy Density Division at SLAC, explained that the situation inside planets like ice giants is complicated because there are many chemicals that affect the formation of diamonds.
“The earlier paper was the first time we directly saw diamond formation from any mixture,” Glenzer said. “Since then, quite a few experiments have been done on different pure materials. We wanted to figure out here what kind of The effect these additional chemicals have.”
Although the team started their experiments with a plastic material composed of a mix of hydrogen and carbon, elements common in ice giants, recent iterations have seen it replaced by PET plastic.
We are familiar on Earth with its use in packaging, bottles and containers, and PET can be used to more accurately replicate the conditions inside ice giants.
“PET has a good balance between carbon, hydrogen and oxygen and can simulate activity in icy planets,” says HZDR physicist and professor at the University of Rostock Dominik Kraus.
Using a high-power optical laser to generate shock waves in PET — part of SLAC’s Matter for Extreme Conditions (MEC) instrument — the team was able to probe what was happening in the plastic using X-ray pulses from the Linac Coherent Light Source. LCLS).
This allowed them to see the atoms in the PET arranged into diamond-shaped regions and measure the growth rate of these regions.
In addition to finding that the diamond-shaped regions grow to a scale of about a few nanometers wide, the scientists also found that the presence of oxygen in the PET means that the nanodiamonds grow at lower pressures and lower temperatures than previously seen.
“The role of oxygen is to accelerate the splitting of carbon and hydrogen, thereby promoting the formation of nanodiamonds,” Krauss said. “This means that carbon atoms can combine more easily and form diamonds.”
Nanodiamonds: Goodies in Small Packages
The research could point the way to a new way to make diamonds smaller than 1 micron in size, called “nanodiamonds,” produced when inexpensive PET plastic is compressed by laser-driven shocks.
“The current way to make nanodiamonds is to use a pile of carbon or diamond and blow it up with dynamite,” said SLAC scientist and team collaborator Benjamin Ofori-Okai. This can create nanodiamonds of various sizes and shapes, and is difficult to control . What we see in this experiment is the different reactivity of the same species at high temperature and high pressure. “
Ofori-Okai added that laser production could provide a cleaner and easier-to-control method of nanodiamond production. “If we can devise ways to change a few things about reactivity, we can change the rate at which they form and thus their size,” he continued.
Nanodiamonds have a wealth of potential applications in medicine, including drug delivery, non-invasive surgery and medical sensors, as well as the growing field of quantum technology. That means scientists’ discoveries may be closer to our home than ice giants lurking in the outer solar system.
Scientists involved in the study will now try experiments with liquid samples containing chemicals such as ethanol, water and ammonia, which are some of the main components of ice giants, to better understand what is happening under the freezing atmospheres of these cold worlds. thing.
“The fact that we can recreate these extreme conditions and see how these processes work on a very fast, very small scale is exciting,” said SLAC scientist and collaborator Nicholas Hartley. “Adding oxygen allows us to do more than ever before. Anytime is closer to seeing the full picture of these planetary processes, but there is more work to be done.
“This is a step towards getting the most realistic mixtures and understanding how these materials really behave on other planets.”
The team’s research is published in the latest issue of the journal scientific progress (opens in new tab).
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