Drifting on an ocean of bling
There’s an old saying they have on Neptune – ‘Nothing is richer than a penguin’. At least, there would be if anything could survive the intense heat and massive pressure it takes to create the ‘icebergs’ of diamond floating on a sea of liquid carbon.
According to a recent article in the journal Nature Physics, diamonds behave a lot like ice when they are melted at high pressures. Stranger still, astronomers believe this might actually be happening on Neptune and Uranus.
Most materials take up less space as they change from a gas into a liquid and then into a solid. But both ice and diamonds contain atoms that line up in such a way that they take up more space as a solid than as a liquid, making them less dense. In other words, under the right circumstances an ocean of liquid diamond could have chunks of diamond floating in it.
Solid carbon can take a range of forms, depending on how the carbon atoms are linked together. Graphite is the black stuff in your lead pencil; every carbon atom in it is linked to another three, forming sheets that slide over one another. Each carbon atom in diamond, on the other hand, is linked to four others, making it quite hard. Yet it takes a tremendous amount of heat and pressure to force carbon into this formation.
Previously, diamond has been difficult to melt in the laboratory without it turning into graphite first. On occasions where scientists have succeeded, they were unable to measure the precise pressure and temperature at which it occurred.
When scientists in California liquefied diamonds at a pressure 40 million times greater than the atmospheric pressure on Earth (what you’re feeling right now), then slowly lowered both the pressure and temperature, they noticed chunks of solid diamond form. Amazingly, it didn’t sink as expected, but floated as ice would on water.
It also turns out that the peculiar properties of a liquid diamond ocean could explain an odd tilt in the magnetic fields of Neptune and Uranus. Given that 10 per cent of their material consists of carbon, it’s possible that their mass could produce the right conditions for liquid diamonds.
All those lucky Neptunian penguins.
