1. Department of Geosciences, Stony Brook University, Stony Brook, NY, USA.
2. To whom correspondence should be addressed.
3. Hawaii Institute of Geophysics and Planetology, University of Hawaii, Hawaii, HI, USA.
4. Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA.
5. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109–8099, USA.
6. Department of Physics, University of Oxford, Oxford, UK.
7. NASA Ames Research Center, Moffett Field, CA 94035–1000, USA.
8. Department of Geological Sciences, Brown University, Providence, RI, USA.
9. NASA Johnson Space Center, Houston, TX 77058, USA.
10. Department of Earth and Space Sciences, University of California, Los Angeles, Los Angeles, CA, USA.