Helium precipitation is possible within the Jovian planets, suggests new experiments. Jupiter, Saturn, and many giant exoplanets discovered to date contain primarily hydrogen and helium. In 1977, planetary scientists predicted the existence of a helium shower layer within these planets.
However, it is not possible to obtain the experimental conditions necessary to validate this hypothesis, until now. An artist’s impression of the ultra-short-period subneptune exoplanet TOI-1634b. We found that helium shower is real and can occur on both Jupiter and Saturn, said physicist Dr. Marius Milot of the Lawrence Livermore National Laboratory.
It is important to help planetary scientists understand how these planets formed and evolved, which is important for understanding how the solar system formed. Jupiter is particularly interesting because it is believed that it helped protect the inner planetary region where Earth forms.
We could be here thanks to Jupiter,” said Professor Raymond JeanLouz of the University of California at Berkeley. In their experiments, the researchers used Diamond Evil cells to compress a mixture of hydrogen and helium to 4 GPa.
He then used 12 giant beams from the Omega Laser Facility at the University of Rochester Laser Energy Laboratory to launch strong shock waves to heat the sample to ultimate pressures of 60-180 GPa and up to several thousand degrees.
Dr Stilot said: Static compression and laser driven shocks are important to allow us to achieve comparable conditions inside Jupiter and Saturn, but it is very challenging. We really had to work on the technology to get solid evidence. It took years and a lot of creativity from the team.
Using a series of ultra-fast diagnostic tools, the scientists measured the shock velocity, the optical reflectivity of the shock-compressed sample, and its thermal emission. They found that the reflectivity of the sample did not increase smoothly with increasing impact pressure.
Instead, they found an imbalance in the observed reflectance signal, indicating that the electrical conductivity of the sample was suddenly changing, a signature of the separation of the helium and hydrogen mixtures.
“Our experiments reveal experimental evidence for a long-standing prediction: there are many pressures and temperatures at which this mixture becomes unstable and unmixed,” said Dr. Milot said.
“This transition occurs under the pressure and temperature conditions necessary to convert hydrogen into a metallic fluid, and the intuitive picture is that hydrogen metallization triggers demixing.”
The team now plans to refine the measurement and extend it to other compositions in an ongoing effort to improve our understanding of the material under extreme conditions. The findings were published in the journal Nature of Science News.