1. Department of Earth Sciences, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
2. Planet Planetary Data Service, Wilhelminastraat 43A, 2011 VK Haarlem, The Netherlands
3. Earth System Science Disciplinary Center, University of Maryland, College Park, MD 20740, USA
4. Biospheric Sciences Laboratory, NASA Goddard Space Center, Greenbelt, MD 20771, USA
5. SRON Netherlands Institute for Space Research, 2333 CA Leiden, The Netherlands