New phase of water could dominate the interiors of Uranus and Neptune : phys.org: by Lisa Zyga
Structure of superionic ice in (left) the bcc phase and (right) the newly discovered and more stable fcc phase. Credit: Hugh F. Wilson, et al. ©2013 American Physical Society
Read more at: http://phys.org/news/2013-04-phase-dominate-interiors-uranus-neptune.html/
Although superionic ice doesn’t exist under normal conditions on Earth, the high pressures and temperatures where it is thought to exist are very similar to the predicted conditions in the interiors of Uranus and Neptune.
“Uranus and Neptune are called ice giants because their interiors consist primarily of water, along with ammonia and methane,” Wilson said. “Since the pressure and temperature conditions of the predicted new phase just happen to line up with the pressure and temperature conditions of the interiors of these planets, our new fcc superionic phase may very well be the single most prevalent component of these planets.”
The researchers predict that understanding superionic ice—particularly the stable fcc phase—will offer insight into these ice giants.
“Uranus and Neptune remain very poorly understood at this stage, and their interiors are deeply mysterious,” Wilson said. “The observations we have are very limited—every other planet in the solar system we’ve visited multiple times, but Uranus and Neptune we’ve just done brief flybys with Voyager 2. What we do know is that they have bizarre non-axisymmetric non-dipolar magnetic fields, totally unlike any other planet in our solar system. We also know that they’re extremely similar in mass, density and composition, yet somehow fundamentally different, because Neptune has a significant internal heat source and Uranus hardly emits any heat at all.”
It’s possible that the predicted bcc-to-fcc phase transition may explain the planets’ unusual magnetic fields, although more research is needed in this area.
“Our results imply that Uranus’s and Neptune’s interiors are a bit denser and have an electrical conductivity that is slightly reduced compared to previous models,” Militzer added.
Understanding Uranus and Neptune’s interiors could have implications far beyond our solar system, as well.
“One thing we’re learning from the Kepler mission is that Uranus-like or Neptune-like exoplanets are extremely common,” Wilson said. “They appear to be more common than Jupiter-like gas giants. So understanding our local ice giants is important, because they’re an archetypal example for a huge class of planets out there in the universe.”