TEMPERATURE-MEASUREMENTS OF SHOCK-COMPRESSED LIQUID-HYDROGEN - IMPLICATIONS FOR THE INTERIOR OF JUPITER

Shock temperatures of hydrogen up to 5200 kelvin were measured optical ly at pressures up to 83 gigapascals (830 kilobars). At highest pressu res, the measured temperatures are substantially lower than predicted. These lower temperatures are caused by a continuous dissociative phas e transition above 20 gigapascals. Because hydrogen is in thermal equi librium in shock-compression experiments, the theory derived from the shock data can be applied to Jupiter. The planet's molecular envelope is cooler and has much less temperature variation than previously beli eved. The continuous dissociative phase transition suggests that there is no sharp boundary between Jupiter's molecular mantle and its metal lic core. A possible convectively quiescent boundary layer might induc e an additional layer in the molecular region, as has been predicted.