Storms on Saturn and Jupiter form hailstones of pure diamond, according to a paper published for the 45th meeting of the American Astronomical Association.
Dr Kevin Baines of the University of Wisconsin-Madison and NASA's Jet Propulsion Laboratory told the delegates that when huge weather systems on the gas giants create storms, the lightning they generate changes atmospheric methane into carbon.
As this carbon falls towards the planet's surface, it hardens into graphite and then the huge pressures generated by the Solar System's largest planets transform the graphite into diamonds that would be big enough to turn into jewelry.
"The bottom line is that 1,000 tonnes of diamonds a year are being created on Saturn," said Baines, the BBC reports. "People ask me – how can you really tell? Because there's no way you can go and observe it. It all boils down to the chemistry. And we think we're pretty certain."
It takes around 6,000km of falling for the carbon to complete its transformation into diamond, but as it falls further into the gas giants it doesn't remain in that form, the scientists suggest. Eventually, around 30,000km down, the diamonds would not be able to survive.
"Once you get down to those extreme depths, the pressure and temperature is so hellish, there's no way the diamonds could remain solid," Baines said. "It's very uncertain what happens to carbon down there. Diamonds aren't forever on Saturn and Jupiter. But they are on Uranus and Neptune, which are colder at their cores."
It has already been suggested that both Uranus and Neptune have cores that are either solid diamond or diamond coated. But Baines said that the relatively higher temperatures of Saturn and Jupiter would mean that the carbon could form in vast liquid seas near the planets' cores.
Professor Raymond Jeanloz, who co-wrote the original paper postulating diamonds in the cores of Uranus and Neptune, said that the new paper has merit, though there are still many other factors to consider.
"The idea that there is a depth range within the atmospheres of Jupiter and (even more so) Saturn within which carbon would be stable as diamond does seem sensible," Jeanloz said. "And given the large sizes of these planets, the amount of carbon (therefore diamond) that may be present is hardly negligible." ®