1. Department of Geosciences, Princeton University, Princeton, NJ 08544, USA.
2. Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA.
3. Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94550, USA.
4. Division of Engineering and Applied Sciences, California Institute of Technology, 1200 E California Boulevard, Pasadena, CA 91125, USA.
5. Laboratory for Laser Energetics, Department of Physics and Astronomy, and Department of Mechanical Engineering, University of Rochester, Rochester, NY 14623–1299, USA.