1. Daniel Guggenheim School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA.
2. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA.
3. Massachusetts General Hospital, Department of Molecular Biology, Boston, Massachusetts, USA.
4. Howard Hughes Medical Institute, Boston, Massachusetts, USA.
5. Current address: Department of Chemistry, University of Chicago, Chicago, Illinois, USA.
6. MIT Department of Electrical Engineering and Computer Science, Cambridge, Massachusetts, USA.
7. Osaka University, Institute of Scientific and Industrial Research, Osaka, Japan.
8. MIT Department of Earth, Atmospheric and Planetary Sciences, Cambridge, Massachusetts, USA.