The Nördlinger Ries and Steinheim Basin, two geological structures in Germany, were traditionally viewed as volcanic edifices until they were recognized as impact craters in the 1960s. The changing views about the craters’ origins mark a paradigm shift in the Earth sciences, from an Earth-centric approach to a planetary perspective that acknowledged Earth’s place in the cosmos. Drawing on a range of printed sources and archival material, Kölbl-Ebert provides a reconstruction of the sequence of events as well as the emotions and motives of the scientists involved and the social context of their research.