1. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA
2. Blue Marble Space Institute of Science, Seattle, WA, USA
3. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
4. Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
5. Institute for Advanced Study, Princeton, NJ 08540, USA
6. Center for Chemical Evolution, Georgia Institute of Technology, Atlanta, GA 30332, USA