S u m m a r y :
‘Diamond rain’, a form of precipitation that is present inside huge icy planets, has been created by a team of scientists from the DOE/SLAC National Accelerator Laboratory. The findings are published in the journal Nature Astronomy.
The aim of the research was to reproduce the conditions characterising the inside of cold, giant planets of our solar system, like Neptune, whereby elements carbon and hydrogen were squeezed at high pressure to form solid diamonds. ‘Diamond rain’ has, as a result, been created for the first time ever. The team used SLAC’s X-ray free-electron laser (Linac Coherent Light Source (LCLS)) and an optical laser of the Matter in Extreme Conditions equipment to achieve the feat in real-time.
The shimmering rain is believed to exist underneath the surface of planets Neptune and Uranus where hydrogen and carbon are thought to be found in abundance. The insides of these heavenly bodies consist of a solid core coated with a variety of ices made of elements like carbon, oxygen, and nitrogen bonded with hydrogen molecules. This type of environment was simulated with shock waves in a type of plastic (polystyrene which is made of hydrogen and carbon) using the SLAC equipment.
“For this experiment, we had LCLS, the brightest X-ray source in the world,” said co-author Siegfried Glenzer from SLAC. “You need these intense, fast pulses of X-rays to unambiguously see the structure of these diamonds, because they are only formed in the laboratory for such a very short time.”
The simulation showed that nearly each atom of carbon making up the plastic was turned into diamond structures with widths of few nanometers only. The diamonds on Neptune and Uranus would be much bigger, though; the researchers mention weights equivalent to millions of carats. These diamonds would eventually seep into the ice layers of the planets to form a thick shell surrounding the core.
This diamond rain has been the object of other research works, but none of these would reproduce it with measurements in real time taken. The limitations met by other scientists were compensated for by the high-energy optical lasers of MEC and the LCLS. The new findings constitute the first clear observation of the formation of diamond from mixtures at high pressure; furthermore, the results appear to be in line with what the world of science have concocted of theories relating to the conditions governing such ‘rain’.
“Previously, researchers could only assume that the diamonds had formed,” said lead author Dominik Kraus. “When I saw the results of this latest experiment, it was one of the best moments of my scientific career.”