1. Department of Geological and Environmental Sciences, Stanford University, Stanford, California
2. Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana
3. Center for Astrobiology, Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California
4. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California
5. Lawrence-Berkeley Laboratory, University of California, Berkeley, California