The NArdlinger Ries and Steinheim Basin, two conspicuous geological structures in southern Germany, were traditionally viewed as somewhat enigmatic but nevertheless definitely volcanic edifices until they were finally recognized as impact craters in the 1960s. The changing views about the origin of the craters mark an important paradigm shift in the Earth sciences, from an Earth-centric approach to a planetary perspective that acknowledged Earth's place in the wider cosmos. Drawing on a range of printed sources, detailed archival material, letters, personal notes, and interviews with veterans...