Shock compression of H-Ne mixtures at gas giant interior conditions*

Ne has been observed to be strongly depleted in the atmospheres of gas giant planets relative to bulk solar compositions [1]. A proposed mechanism for this depletion is the phase separation of Ne from H, the main component of gas giant atmospheres [2]. While recent work shows that H and He phase-separate at conditions present in the outer layers of Jupiter and Saturn [3], the miscibility of Ne with other planetary components at similar conditions has yet to be experimentally constrained. We combined static and dynamic compression to investigate the equation of state and reflectivity (an indicator of miscibility) of H-Ne (20% mol Ne) at the conditions of gas giant interiors. The novel band gap behavior or Ne, whereby it is predicted to remain insulating into the warm dense regime [4], could have a bearing on these results. Contrary to expectation, the data indicate mixing of H and Ne at temperatures up to 20,000 K and pressures up to 150 GPa. Follow-up experiments will utilize different mixing ratios and probe a wider range of pressure-temperature conditions. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

[1] Niemann et al., Science 1996

[2] Wilson and Militzer, Phys. Rev. Lett., 2010

[3] Brygoo et al., Nature, 2021

[4] Tang, J., Chem. Phys., 2019