Lab Reproduces Neptune’s Diamond Rain, Revealing Diamonds Form Deep Inside Ice Giants

Scientists at SLAC used ultrafast laser-driven shocks on a hydrocarbon surrogate to mimic Neptune’s deep-interior pressures and temperatures, triggering carbon to crystallize as nanometer-scale diamonds in a femtosecond window and confirming the long-predicted “diamond rain.” Subsequent work shows these conditions can occur at lower thresholds than first thought, implying diamond rain could occur over a broader region of Neptune’s and Uranus’s interiors, potentially influence magnetic fields, and hint at diamond-rich mantles in many exoplanets.