Comet Shoemaker–Levy 9 about 50 arcseconds long and 10 arcseconds wide. Brian G. Marsden of the Central Bureau for Astronomical Telegrams noted that the comet lay only about 4 degrees from Jupiter as seen from Earth, and that although this could of course be a line of sight effect, its apparent motion in the sky suggested that it was physically close to it. Because of this, he suggested that the Shoemakers and David Levy had discovered the fragments of a comet that had been disrupted by Jupiter's gravity. Orbital studies of the new comet soon revealed that it was orbiting Jupiter rather than
Eugene Merle Shoemaker Institute in 1965. Coming to Caltech in 1969, he started a systematic search for Earth orbit-crossing asteroids, which resulted in the discovery of several families of such asteroids, including the Apollo asteroids. Shoemaker advanced the idea that sudden geologic changes can arise from asteroid strikes and that asteroid strikes are common over geologic time periods. Previously, astroblemes were thought to be remnants of extinct volcanoes — even on the Moon. In 1993, he co-discovered Comet Shoemaker–Levy 9 using the 18-inch Schmidt camera at Palomar Observatory. This comet was unique in that it provided the first opportunity to observe the planetary