Space
Does it rain diamonds on Neptune?
The short answer
Very probably, and in 2017 scientists made it happen on Earth. Deep inside Neptune and Uranus, pressure and heat are thought to squeeze carbon out of methane and crush it into diamonds that sink toward the core. A team at the SLAC National Accelerator Laboratory recreated those conditions with a laser and watched diamonds form.
Neptune and Uranus are called ice giants, but the ice is not the kind in a freezer. Thousands of kilometres down, water, ammonia and methane are squeezed to pressures millions of times higher than Earth's atmosphere and heated to thousands of degrees. Theory has long said that under those conditions methane should break apart and its carbon should lock together into diamond.
In 2017 researchers fired an intense optical laser at a piece of plastic, a stand-in for methane because it is also made of hydrogen and carbon, to create a shock wave that briefly reached the right pressure and temperature. An X-ray laser flashed through the sample at the same instant and caught the carbon atoms snapping into diamond structure. It took about a billionth of a second.
On the planets, those diamonds would sink slowly through the slushy interior like hailstones, possibly growing for thousands of years on the way down. Nobody has seen it, and nobody will soon. But the recipe has been tested, and it works.
Sources
- Scientists Create 'Diamond Rain' That Forms in the Interior of Icy Giant PlanetsSLAC National Accelerator Laboratory
- Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditionsNature Astronomy