Ellen Knappe, University of Montana, Missoula, MT, United States, Rebecca O Bendick, University of Montana, Geosciences, Missoula, MT, United States, Hilary R Martens, California Institute of Technology, Pasadena, CA, United States, Donald F Argus, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States and William Payton Gardner, Sandia National Laboratories, Albuquerque, NM, United States