Scientists think it rains diamonds inside Saturn, with roughly 1,000 tons forming each year as lightning storms shatter methane into carbon soot, which the planet’s crushing pressure compresses into gems before they sink toward a possible ocean of liquid diamond at the core

The idea that it rains diamonds inside Saturn is a model of an inaccessible planetary interior, not an observation. No camera has seen the gems and no probe has sampled the depths at which they might form. The model begins with something Cassini did observe: …