Fig. 1

Examples of secondary crater fields (McEwen and Bierhaus 2006). (a) A secondary crater chain with herringbone patterns from the lunar crater Copernicus (located < 350 km to the southeast). Superimposed (younger) secondary clusters may have come from Aristarchus, 580 km to the west (Masursky et al. 1978). Randomly distributed small craters in this image may be distant secondaries or small primaries. Scale bar 10 km. Apollo 17 AS17-P-3093 (NASA); (b) a cluster of secondary craters on Mars in Amazonis Planitia, which originated from Tooting, a young 29-km-diameter crater located < 100 km to the north. Scale bar 500 m. MOC S05-00491 (NASA/JPL/MSSS); (c) clusters of impact craters on Europa. The secondaries from Aristarchus and those on Europa are distant secondaries (>10 times the radius of the primary crater). Scale bar 5 km. Galileo mosaic E17STRSLP01 (NASA/JPL/ASU)