Testing our theories about other planets without actually have the tools to explore other planets to the greatest of depths is a challenge. We got lucky with Ryugu, and Nature broke it apart for us. With other planets, we just have to do the best we can by simulating their environments in our laboratories. Extreme environments, however, have remained beyond our technical limitations, and our ability to simulate things in a lab is just starting to catch up to our ability to imagine them in software.
In a new experiment at the University of Rochester’s Laboratory for Laser Energetics, researchers used diamond anvils to compress a mixture of hydrogen and helium to pressures like those expected in Saturn’s atmosphere; pressures 40,000 times what we experience on Earth. They then used shock waves from lasers to compress things by another factor of 15-45, and they looked to see what happened. According to study co-author Marius Millot: Our experiments reveal experimental evidence for a long-standing prediction: There is a range of pressures and temperatures at which this mixture becomes unstable and demixes.
Put another way, he says: We discovered that helium rain is real, and can occur both in Jupiter and Saturn. This work appears in Nature and is led by S. Brygoo. We would like to remind all of you not to try singing or dancing in the helium rain because the conditions will kill you.
LLNL press release
“Evidence of hydrogen−helium immiscibility at Jupiter-interior conditions,” S. Brygoo et al., 2021 May 26, Nature