Comet Shoemaker–Levy 9 by the comet fragments punching through the upper atmosphere. Spectroscopic studies revealed absorption lines in the Jovian spectrum due to diatomic sulfur (S) and carbon disulfide (CS), the first detection of either in Jupiter, and only the second detection of S in any astronomical object. Other molecules detected included ammonia (NH) and hydrogen sulfide (HS). The amount of sulfur implied by the quantities of these compounds was much greater than the amount that would be expected in a small cometary nucleus, showing that material from within Jupiter was being revealed. Oxygen-bearing molecules such as sulfur dioxide were not detected, to
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