'Oceans of diamonds' on Uranus and Neptune
Oceans of liquid diamond topped with solid "icebergs" of the precious gems could be on Uranus and Neptune, new research has revealed.
Published: 7:30AM GMT 22 Jan 2010
In laboratory conditions which simulated pressure levels on Neptune and Uranus, the scientists found crystals of solid diamond formed like icebergs in the liquid carbon they created The first ever detailed research into the melting point of diamond found it behaves like water during melting and freezing - with its solid form floating on the liquid.
A large diamond ocean on one or both of the planets could provide an explanation for an oddity they both share.
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Flawless blue diamond, one of the world's rarest gems, expected to sell for £6mThe two giant gas planets, unlike Earth, do not have magnetic poles which match up with their geographical poles.
As much as 10 per cent of both planets is carbon, and a liquid diamond ocean could deflect the angle of the magnetic field out of alignment with the planet's rotation, the researchers believe.
In laboratory conditions which simulated pressure levels on the gas planets, the scientists found that little crystals of solid diamond formed like icebergs in the liquid carbon they created.
Dr Jon Eggert, of the Laser Shock Equation of State (EOS) group in the Department of Physical and Life Sciences Directorate at Lawrence Livermore National Laboratory in California, said: "The idea of significant quantities of pure carbon existing in giant planets such as Uranus and Neptune has gained both experimental and theoretical support.
"It is now accepted that the high-pressure, high-temperature behaviour of carbon is essential to predicting the evolution and structure of such planets.
"An ocean of diamond could help explain the orientation of Uranus' and Neptune's magnetic field."
The researchers took a half-millimetre wide diamond a tenth of a carat in weight and blasted it with lasers at high pressure, similar to that which found on Uranus and Neptune.
The diamond was liquified at pressures 40 million-times greater than at sea-level on Earth, and from there the scientists slowly reduced the temperature and pressure.
When the pressure fell to only 11 million-times Earth sea level and temperatures dipped to 50,000 degress Celsius, solid chunks of diamond began to appear in the liquid.
As the pressure continued to drop more and more chunks formed in the liquid diamond, and did not sink.
With most materials the solid state is more dense than the liquid state - with water one of the few exceptions.
Dr Eggert went on: "Diamond is relatively common material on Earth, but its melting point has never been measured.
"You can't just raise the temperature and have it melt, you also have to go to very high pressures, which makes it very difficult to measure the temperatures."
The new article is published in the journal Nature Physics.