Troughs on asteroid Vesta are evidence of tectonics

Images from the Dawn spacecraft, which approached the asteroid Vesta in July 2011, show large‐scale linear troughs on the asteroid's surface. To find out more about how these structures may have formed, Buczkowski et al . analyzed their sizes and shapes. The orientation of the structures around impact craters on Vesta implies that their formation is related to impact events. The authors note that other asteroids display fractures or grooves around impact craters. However, the size and morphology of the structures on Vesta are more similar to those of faults on terrestrial planets. The authors suggest that Vesta's large faults were able to form because Vesta, unlike many other asteroids, is differentiated—it has a layered structure consisting of a crust, mantle, and core with inherent different rock types, densities, and strengths. Smaller grooves and fractures, but not large faults, would form on undifferentiated asteroids. Their analysis also indicates that the features are not necessarily a single long fault but rather at least two large linking faults. ( Geophysical Research Letters , doi:10.1029/2012GL052959, 2012) —EB