Ask a planetary scientist, and they will tell you that diamonds aren’t really all that uncommon. In fact, there are billions of tons of them hiding away in the deep interiors of planets in our solar system and beyond. The most enthusiastic will tell you about diamond rain—where a planet’s temperature and pressure are so great that diamond literally melts and forms a liquid, dropping toward the planet’s core.

The friction and heat these diamond raindrops generate are among the primary drivers of Neptune’s excess energy, which it then radiates back out into space. For the first time, the LLNL paper provides solid experimental data on the precise pressures and temperatures needed for such an awe-inspiring event to occur.