But no one could prove that this would really work — until now. In a study published this week in the journal Nature Astrophysics, researchers say they were able to produce this "diamond rain" using fancy plastic and high-powered lasers.
“Previously, researchers could only assume that the diamonds had formed,” lead author Dominik Kraus, a physicist at the Helmholtz Dresden-Rossendorf research center in Germany, told the magazine Cosmos. “When I saw the results of this latest experiment, it was one of the best moments of my scientific career.”
Scientists have tried to do this before — who wouldn't want to make it rain precious stones? — but they ran into problems mimicking the incredible pressures near the gas planet's cores. Neptune and Uranus are 17 and 15 times the mass of Earth, respectively, and their oceans are crushed by pressures millions of times more intense than the air pressure at Earth's sea level.
To match this absurd intensity, Kraus and his colleagues used two types of laser — one optical, one X-ray — to produce shock waves. These waves were then driven through a block of polystyrene — a type of plastic composed of hydrogen and carbon, just like Uranus and Neptune's oceans.
“The first smaller, slower wave is overtaken by another stronger second wave,” Kraus explained in a news release. The combination of the two waves squeezed the plastic to 150 gigapascals of pressure — more than exists at the bottom of Earth's mantle — and heated it to more than 8,500 degrees. At that moment, the diamonds began to form.
The process lasted only a fraction of a second, and the diamonds were no bigger than a nanometer in length. But Kraus and his colleagues believe that the diamonds that develop on Uranus and Neptune are probably bigger and longer-lasting.
“In the planet you have years, millions of years, and a long range of conditions where this actually can happen,” co-author Dirk Gericke, of the University of Warwick, told the Guardian.
The results will be useful not just for understanding the outer gas giants but for improving the process of making diamonds. Most lab-grown stones are produced via a blasting process, but Kraus and Gericke suggest that using lasers may make production cleaner and easier to control. Those stones can then be used for semiconductors, drill bits and solar panels, not to mention instruments that mimic the conditions inside the very gas planets that inspired this research.