Historians of science have long recognized the field as a socially heterogeneous space wherein different groups jostle for access and to assert the priority of their activities. This essay offers a new take on this heterogeneity by considering recreation as a form of moralized social belonging that scientists bring to the field. In the 1940s, when North American glaciology was emerging as a military-supported geophysical science, many glaciologists were also mountaineers. The essay analyzes a dispute between a mountaineer and a (...) scientist-mountaineer that took place at this time, in which the scientist turned to mountaineering ethics to confront accusations of pseudoscience. The dispute is unintelligible unless one recognizes mountaineering as a form of social belonging with its own ends, techniques, standards, and virtues, capable of influencing how scientists negotiate life in the field. On this account, social heterogeneity and the means for navigating it not only arise through borrowings and appropriations from other social groups but are brought to the field through scientists’ prior commitments to other forms of social life. This suggests a new role for recreation in the history of science: identification with an avocational pursuit may shape moral and social life in the field. (shrink)