The first time and only time I’ve been to the United States was when I carried out a summer placement at the SLAC National Accelerator Laboratory. To get there, I had to have an interview at the U.S. embassy, where when asked what I was going to do in the U.S. I said that I’d be making diamonds. My interviewer laughed at me. But it was true, that was the experiment I was going to help out with. And now, a research collaboration of scientists from all over the world have, for the first time, created ‘diamond rain’ in the laboratory to mimic the conditions of the interiors of icy giant planets. Dominik Kraus, scientist at Helmholtz Zentrum Dresden-Rossendorf, described this work as ‘one of the best moments of my scientific career’.
Icy giant planets like Neptune and Uranus in our solar system, are planets with a gaseous atmosphere and a rocky core surrounded by a dense slush of different ices. The ices are generally hydrocarbons made of heavier elements including oxygen, carbon, sulfur and nitrogen bonded to hydrogen. Under extremely high pressures, ‘diamond rain’ can be seen deep inside their interiors. This occurs when the hydrogen and carbon are squeezed by extreme pressures to form solid diamonds. They then slowly sink towards the center of the icy giant forming a layer around the rocky core, just like rain sinks in our atmosphere towards the surface of Earth.
Researchers from Germany, Japan, the United States and the UK carried out experiments at the Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory to mimic the ‘diamond rain’ within the interior of icy giant planets. This field of work which consists of recreating astrophysical environments is known as laboratory astrophysics. It is a way of simulating large astrophysical events on small spatial and temporal scales in the laboratory where parameters can be changed in order to learn more about the Universe we live in. ‘We can’t go inside the planets and look at them, so these laboratory experiments complement satellite and telescope observations,’ says Kraus, lead author of the Nature Astronomy paper that describes this work.
The ‘diamond rain’ was created in the laboratory by producing extreme conditions of high pressure and temperature in polystyrene, a plastic which was used to mimic methane, the element that leads to the unique blue color of Neptune. Methane is a hydrocarbon where each methane molecule comprises of four hydrogen atoms bonded to a single carbon atom. An intense optical laser at the Matter in Extreme Conditions (MEC) instrument at LCLS was used to generate a pair of shock waves in the polystyrene. The first smaller and slower shock was overtaken by a stronger second shock in order to create the perfect conditions for diamond formation.
The diamonds formed were only a few nanometers (hundreds of a millionth of a meter) in diameter and lived for about 50 femtoseconds, in other words, 50 quadrillionths of a second. Therefore, just like the flash of a camera is used to capture a moment in time, a short pulse of light is needed to capture a snapshot of this very fast reaction. The short pulses of light used were the short pulses of x-rays from ‘LCLS, [the] brightest x-ray source in the world’ says Siegfried Glenzer, professor of photon science at SLAC. Snapshots of the nanodiamonds were taken at different times during the diamond formation to obtain details of the reaction and the size of the diamonds.
Scientists have speculated that the diamonds formed on planets like Uranus and Neptune are possibly millions of carats in weight and form over thousands of years. As a result, this work paves the way for learning more about the interiors of icy giant planets. Planets are classified by their mass and radius, therefore, by understanding the interior processes of planets, the way planets are modelled and classified could change too. Moreover, being able to create nanodiamonds on Earth could potentially be useful for applications in medicine, electronics and scientific equipment.
Scientists Make It Rain Diamonds In The Lab – Forbes