Comet Shoemaker–Levy 9 the Cretaceous period is generally thought to have been caused by the Cretaceous–Paleogene impact event, which created the Chicxulub crater, demonstrating that impacts are a serious threat to life on Earth. Astronomers have speculated that without Jupiter to mop up potential impactors, extinction events might have been more frequent on Earth, and complex life might not have been able to develop. This is part of the argument used in the Rare Earth hypothesis. In 2009, it was shown that the presence of a smaller planet at Jupiter's position in the Solar System might increase the impact rate of comets on
Carolyn S. Shoemaker Carolyn S. Shoemaker Carolyn Jean Spellmann Shoemaker (born June 24, 1929) is an American astronomer and is a co-discoverer of Comet Shoemaker–Levy 9. She once held the record for most comets discovered by an individual. Carolyn Jean Spellmann was born in Gallup, New Mexico, United States. to Leonard and Hazel Arthur Spellmann. Her family moved to Chico, California, where she and her brother Richard grew up. Carolyn Spellmann earned bachelor's and master's degrees in history, political science, and English literature from Chico State University. Richard went to the California Institute of Technology (Caltech), where he earned a bachelor's degree in