Scientists reveal it's raining diamonds on Neptune

The Matter in Extreme Conditions instrument at SLAC gives scientists the tools to investigate the extremely hot dense matter at the centers of stars and giant planets

This is the first time the reaction has been seen, adding evidence to the theory that diamonds form this way in the planets' interiors.

While the glittering precipitation has always been hypothesised, this is the first time that scientists have observed it in practice.

The planet's unique high-pressure environment and methane-heavy atmosphere means that carbon atoms are regularly compressed into diamond, before raining down on the planet's surface, sinking into the ground, and developing a crystalline core - its neighbor Uranus has a similar makeup.

The researchers from HZDR and SLAC were joined by scientists from the University of California in Berkeley, the Lawrence Livermore National Laboratory, the Lawrence Berkeley National Laboratory, the GSI Helmholtzzentrum für Schwerionenforschung, the University of Osaka, TU Darmstadt, the European XFEL, the University of MI, and the University of Warwick.

The experiment caused nearly all the carbon atoms in the plastic to combine into diamond-like structures a few nanometers wide. "Our experiments show that almost all the carbon atoms compact into nanometer-sized diamonds", the Dresden researcher summarizes. The researchers theorize that the diamonds sink into the interior of these planets and shape a gleaming crust around their solid cores.

On Uranus and Neptune, the study authors predict that diamonds would become much larger, maybe millions of carats in weight. On the other hand, when he saw the results of this current experiment, he described it as one of the best moments of his scientific career. The structure of the methane atmosphere combined with the high pressure of the gas giants suggests that at depths of around 5,000 meters into the atmosphere, the tiny diamonds are forming and then slowly falling through the gasses as a "slush" that eventually settles around the core of the planets, generating heat in the atmosphere in the process.

This was achieved by sending two shock waves through the samples, triggered by an extremely powerful optical laser in combination with the X-ray source Linac Coherent Light Source (LCLS) at SLAC.

"The first smaller, slower wave is overtaken by another stronger second wave", Dominik Kraus explains. The team were also able to "see" the diamonds being formed, using very short pulses of X-rays.

The findings can help scientists understand how elements within planets interact with one another under pressure.

The scientists are now planning to use these methods to search for other activities that happen inside the other planets.

"We can't go inside the planets and look at them, so these laboratory experiments complement satellite and telescope observations", Kraus said.

The experts say that the nanodiamonds made on Earth could potentially be harvested to make the tips of precision medical instruments, or used in electronics.



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