METALLIC DEUTERIUM. Livermore physicists have the best evidence yet that deuterium, a heavy form of hydrogen, is metallic at pressures as low as 50 GPa with temperatures near 8000 K. These conditions are near those expected in Jupiter's interior. The experiment in question uses the powerful Nova laser to push a plunger which in turn sets up a shock wave and high pressures in a sample of liquid deuterium. At pressures as low as 20 GPa the deuterium shows both an increasing compressibility (meaning that D2 molecules are being dismembered and crushed together; see figure at Physics News Graphics) and increasing reflectance (one sign of metallic behavior is that the sample reflects rather than absorbs or transmits light) with rising pressure.

The transition from insulator to metal is continuous and at any one time the liquid may be a mixture of D atoms, D ions plus electrons free to roam, and even a few D dimers (2-atom molecules), trimers, tetramers, etc. Previous work with metallic hydrogen suggested that the Jupiter's metallic core was larger than originally thought. This new work (Peter Celliers, 925-424-4531), with deuterium hints further that because of the continuous metalization transition there may be no distinct boundary inside Jupiter between the metal core and the outer molecular envelope. (Celliers et al., Physical Review Letters, 12 June /pnu/2000/; Select Article.)