Uranus and Neptune may not be ‘ice giants’ after all

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By Hannah Richter, Science. 

Excerpt: For decades, elementary students learned the same tale of the Solar System: first come rocky terrestrial planets such as Earth, followed by gas giants such as Jupiter and ice giants such as Neptune, with lovable Pluto bringing up the rear. ...the so-called ice giants likely contain very little ice. ...Uranus and Neptune were first called ice giants because they orbit past the Solar System’s so-called ice lines: the points beyond which water, ammonia, carbon monoxide, and other volatile molecules exist as solids rather than gases. If this region abounded with frozen water during the early Solar System, then Uranus and Neptune’s interiors might consist mostly of water, squeezed by the pressure of the planets’ gravity into a hot “supercritical” soup. ...researchers have come up with a smorgasbord of ideas about the interiors of our outermost planets. The newest, posted as a preprint last week and currently in review at The Astrophysical Journal, suggests that Uranus and Neptune hold oceans of molten rock. Studies of exoplanets inspired the idea, explains Edward Young, a planetary scientist at UC Los Angeles.... 

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