This paper introduces a special collection of Anthropological Quarterly for examining “the extreme” in contemporary modernity. Drawing upon sites of political, scientific, and economic engagement that source specifically to the extraterrestrial, we argue that the figure of the extreme shapes an analytic of limits and ever-opening horizons—epistemological and physical—provoking new understandings of humanness, environment, temporality, and of inter-species life as we think we understand it, here on Earth. It follows that this framework is not restricted to the environment of outer space: the analytic of the extreme, which is broadly salient in contemporary imagination and social practice, opens to examination of how all modern subjects are capable of upending modernity’s everyday spaces and timelines. The assembled papers cohere around this commitment. Coming in from very different angles, each seriously considers the possibility of outcomes not anticipated by analytic or vernacular explanatory frameworks, while refusing to commit anthropologists to the dangers of prognostication.