Thomas R. Watters is a Senior Scientist in the Smithsonian Institution's Center for Earth and Planetary Studies at the National Air and Space Museum and Director of the Smithsonian's Regional Planetary Image Facility. He is involved in three planetary missions: Mars Express (MARSIS Radar Sounder team), MESSENGER (MDIS imaging team), and the Lunar Reconnaissance Orbiter (LROC imaging team). He has served as Chair of the Planetary Geology Division of the Geological Society of America, guest editor for Geophysical Research Letters, and on the editorial board of the journal Geology. His research interests are planetary tectonics, and planetary geology and geophysics. Richard A. Schultz is Professor of Geological Engineering and Geomechanics at the University of Nevada, Reno, where he teaches courses in geology, rock mechanics, and planetary science. He has served on the IUGS Commission on Comparative Planetology, as associate editor for the Journal of Geophysical Research, guest editor for the Journal of Structural Geology, and co-editor of the 35th U.S. Symposium on Rock Mechanics and the 33rd Symposium on Engineering Geology and Geotechnical Engineering, with visiting professorships at Woods Hole Oceanographic Institution and the University of Paris. His research interests include the evolution of fault systems on various planetary bodies.