DIAMOND OCEANS POSSIBLE ON URANUS, NEPTUNE

From: http://news.discovery.com/space/diamond-oceans-jupiter-uranus.html

Oceans of liquid diamond, filled with solid diamondicebergs, could be floating on Neptune and Uranus, according to a recent article in the journal Nature Physics.

The research, based on 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 Eggert. "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."

...Ultrahigh pressures, the kind of pressures found in huge gas giants like Neptune and Uranus are some of the places where ultrahigh temperatures and ultrahigh pressures exist. Eggert and his colleagues placed a small, natural, clear diamond, about a tenth of a carat by weight and half a millimeter thick, and blasted it with lasers at ultrahigh pressures.

The scientists liquefied the diamond at pressures 40 million times greater than what a person feels when standing at sea level on Earth. From there they slowly reduced the temperature and pressure.

When the pressure dropped to about 11 million times the atmospheric pressure at sea level on Earth and the temperature dropped to about 50,000 degrees solid chunks of diamond began to appear. The pressure kept dropping, but the temperature of the diamond remained the same, with more and more chunks of diamond forming.

Then the diamond did something unexpected. The chunks of diamond didn't sink. They floated. Microscopic diamond ice burgs floating in a tiny sea of liquid diamond. The diamond was behaving like water.

...Up to 10 percent of Uranus and Neptune is estimated to be made from carbon. A huge ocean of liquid diamond in the right place could deflect or tilt the magnetic field out of alignment with the rotation of the planet.