Scientists have confirmed that it literally rains liquid helium deep inside the planet Saturn.
April 1, 2026
Original Paper
Hydrogen-helium immiscibility boundary in planets
arXiv · 2603.28927
The Takeaway
Under the extreme pressures found in gas giants, hydrogen and helium separate like oil and water. This research demonstrates that helium forms droplets that fall as rain toward the planet's core, explaining why Saturn is significantly warmer and structured differently than Jupiter.
From the abstract
The location of the hydrogen-helium (H/He) immiscibility boundary controls whether and where helium rain occurs in giant planets, yet it remains uncertain because high-pressure experiments are challenging and ab initio simulations are limited in system size and simulation time. We map this boundary by computing composition-dependent chemical potentials from large-scale molecular dynamics driven by machine learning potentials trained on three density functional approximations (PBE, vdW-DF, and th