Science: Uranus and Neptune may not be ice giants after all

A study submitted to The Astrophysical Journal suggests Uranus and Neptune may be better described as "magma-ocean giants" rather than ice giants, researchers from the University of California said. The team simulated interior models finding that a well-mixed magma ocean with dissolved hydrogen at the bottom and a hydrogen-dominated envelope at the top best fits the planets' properties. This mixing might explain the planets' density traditionally interpreted as evidence for an ice-rich interior. The long-standing hypothesis holds that both worlds have a hydrogen-helium atmosphere covering a mantle of water, ammonia and methane ices with a rocky core. The researchers note Kuiper Belt objects, thought to preserve evidence of the material where the planets formed, are primarily composed of rock rather than ice. NASA's Voyager 2 remains the only spacecraft to have visited the planets, flying by Uranus on January 24, 1986, and Neptune on August 25, 1989. The findings could help scientists understand the interior structure of sub-Neptune exoplanets in the Milky Way.