The icy giants of our solar system, Uranus and Neptune, may have a surprising secret hidden beneath their frozen surfaces. A new study suggests that these distant planets might actually harbor magma oceans instead of the icy shells we once thought they had. This groundbreaking research, led by planetary scientist Edward Young and his team at UCLA, challenges our understanding of these planets' internal structures and could have significant implications for exoplanet research.
The Ice Giant Model and its Origins
For decades, the standard model of ice giants like Uranus and Neptune has been a small rocky core, a thick shell of water, ammonia, and methane ices, and a hydrogen-helium atmosphere. This model, which originated with German-American astronomer Rupert Wildt in the mid-20th century, was confirmed by NASA's Voyager 2 spacecraft during its flybys of Uranus in 1986 and Neptune in 1989. However, recent data has revealed that these planets contain much less hydrogen and helium by mass, leading astronomers to restrict the term 'gas giant' to Jupiter and Saturn.
A Magma Ocean Alternative
Young's team's new model, posted on the arXiv preprint server on June 16, 2026, and submitted to The Astrophysical Journal for peer review, emerged from Young's studies of sub-Neptune exoplanets. While modeling a planet with an iron core, rocky mantle, and hydrogen envelope, Young identified a physical mechanism where high pressure forces hydrogen gas to dissolve directly into the rocky mantle, lowering the melting point of the rock and causing it to melt fully. When this mechanism was applied to Uranus and Neptune, it yielded a dynamic interior structure featuring a supercritical ocean of magma mixed with dissolved hydrogen.
Implications for Exoplanet Research
This magma ocean model is still a hypothesis awaiting further verification. Confirming it will require dedicated orbital missions to gather long-term data. Space agencies have proposed concepts for two such missions: the Uranus Orbiter and Probe, and Neptune Odyssey. These missions could not only provide a more comprehensive understanding of Uranus and Neptune but also serve as local analogs for thousands of distant sub-Neptune exoplanets, advancing our knowledge of these common planet types in the galaxy.
