Richard Gregory Vaughan¹, Jefferson D G Hungerford², Michael P Poland³ and William Keller², (1)USGS Astrogeology Science Center, Flagstaff, AZ, United States, (2)National Park Service, Yellowstone Center for Resources, Yellowstone National Park, WY, United States, (3)USGS, Yellowstone Volcano Observatory, Vancouver, WA, United States