In laboratories and computers, shocked and squeezed matter turns metallic, coughs up diamonds and reveals Earth's white-hot center

think of each planet’s interior as a giant foundry specialized for processing a particular chemical composite under extreme conditions. These composites range from the simple hydrogen-helium mixture of Jupiter and Saturn to the more complex mixture of “ices” (water, ammonia and methane) that compose Neptune and Uranus, and finally to the mostly “solid” internal structures (silicates plus iron in solid and sometimes liquid form) of terrestrial planets such as Mars, Venus and of course Earth. “Solid” here is a bit of a stretch; over geological time planetary-scale objects made of rock, metal or ice deform and exhibit convection just as fluids do. Likewise the substances we call ices are not strictly solid; they exist as gases in the outer atmospheres of giant planets and as