Two Planets We've Been Calling Ice Giants May Be Full of Magma

Uranus and Neptune have been wearing the "ice giant" label for decades. The name comes from longstanding models placing an icy mantle beneath their hydrogen/helium atmospheres. Turns out we may have had them completely backwards.

A study suggests the two planets harbor a magma ocean in their interiors and may be better described as "magma-ocean giants." The distinction is not cosmetic. Standard models gave both worlds a hydrogen/helium atmosphere over a vast mantle of "ices" comprised of water, ammonia and methane, then a rocky core. But their magnetic fields and heat distribution have never quite fit. The magma model cleans up some of that confusion, and does it using a notably simpler set of assumptions than the old model needed, while still matching everything astronomers actually know about these planets' size, density, and how they radiate heat.

Here is where it gets genuinely strange. This magma would be nothing like what oozes from Earth's volcanoes. Under the extreme pressures and temperatures inside Uranus and Neptune, rock, ice and gas blend together with enormous amounts of hydrogen dissolved into molten rock, less like lava, more like vinegar and oil shaken hard into something new.

Recast as magma-ocean worlds, Uranus and Neptune stop being solar system oddities and become local examples of a planetary class astronomers observe constantly around other stars.

The two most neglected planets in the solar system turned out to be secretly molten.

Read the full story at Universe Today, June 26, 2026

Hot Take: The universe remains undefeated at making our tidy categories look stupid.