Fractured Impact Melt
December 7, 2012
Thales is a young, 32 km diameter crater located at 61.8°N, 50.3°S. The interior of Thales has many different features including terraces formed by slumping and impact melt. Today's Featured Image illustrates the dynamic nature of Thales, with smooth impact melt implaced at the time of impact, which then fractured and was subsequently sprinkled with boulders from a neighboring slope. Impact melt is instant lava, formed when lunar rock is melted when the tremendous energy of impact is released in a moment. After the initial impact, the melt can end up anywhere in the crater. It can pool in the bottom of the crater floor, pool on terraces, or flow down crater walls inside and outside of the rim. Sometimes melt is thrown out of the crater during the impact and lands outside the crater forming pools outside the rim. The cracks in the impact melt probably formed as the melt cooled and solidified. With the cooling of the material comes a change in volume, which could open the cracks. Or, the cracks may have formed over time as the crater floor slowly changed shape and the impact melt material cracked to compensate. Cracks in impact melt inside Thales crater. The smooth impact melt is fractured and then sprinkled with boulders from the neighboring slope. LROC NAC M157270357R, image scale is 0.53 meters/pixel, incidence angle is 62° [NASA/GSFC/Arizona State University].