The impact melt fractures in the Featured Image are located in the impact melt pools outside of the crater Wiener F. Wiener F is a 47 km diameter crater on the farside, located at 40.89°N, 149.94°E. Impact melt is formed during the crater excavation process due to the intense heating of the target rocks. The fractures seen here most likely formed as the impact melt pool cooled. Exterior melt ponds are often seen with fresh craters of this size or larger. For example, the crater Anaxagoras has exterior melt pools, including many fractures. Wiener F is also interesting because it is superposed over a much older impact crater. In the LROC WAC context image below, you can see the remains of the northern rim of the older crater. The interior of Wiener F has been modified by slumping, which may be due to the irregularity of the terrain of the target material (the rim of the older crater).
A few weeks ago, another Featured Image described the exterior impact melt of Wiener F, but for an area closer to the rim of the crater. During the excavation stage of the impact, ejecta scoured the rim and an impact melt veneer covered the scoured area. The impact melt veneer from the earlier Image and the exterior impact melt ponds in today's Image are different due to the volume of impact melt emplaced at each location.
Explore the entire NAC frame for more interesting impact melt features!
Posted by Sarah Braden on October 26, 2012 13:29.