A recent article in Nature Physics argues that oceans of liquid diamond, filled with solid diamond icebergs, could be floating on Neptune and Uranus. More info at Discovery News.
The research, based on the first detailed measurements of the melting point of diamond, found diamond behaves like water during freezing and melting, with solid forms floating atop liquid forms. The surprising revelation gives scientists a new understanding about diamonds and some of the most distant planets in our solar system.
"Diamond is a relatively common material on Earth, but its melting point has never been measured," said J. H. Eggert of Lawrence Livermore National Laboratory in Livermore, Calif. "You can't just raise the temperature and have it melt, you have to also go to high pressures, which makes it very difficult to measure the temperature."