University of Tennessee, Department of Earth and Planetary Sciences, Knoxville, TN 37996, USA; NASA Goddard, Goddard Spaceflight Center, Greenbelt, MD 20771, USA
Planetary Science Institute, 1700 E. Ft. Lowell Rd. Suite 106, Tucson, AZ 85719, USA
Geological Survey of Canada, 601 Booth Street, Ottawa, ON K1A 0E8 Canada
University of Tennessee, Department of Earth and Planetary Sciences, Knoxville, TN 37996, USA