The temperature of shock compressed iron has been measured to 340 GPa, using well characterized iron films sputtered on transparent diamond substrates and a 1 ns time-resolved optical method. We find a knee on the (P,T) iron Hugoniot indicating melting at 6350 K and 235 GPa and at 6720 K and 300 GPa. An extrapolation yields an iron melting temperature of 6830 (± 500) K at 330 GPa, the pressure of the Earth inner-outer core boundary. Implication of the melting data for the iron phase diagram is also discussed.

• Received 13 October 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.3931