Human spaceflight has been evaluated largely through physiological endurance and operational success. A more fundamental question has gone unasked: whether cognition remains viable when the environmental conditions that have always accompanied human life are radically altered. This article argues, from ecological-enactive theories of cognition, that human cognition is constituted through ongoing organism-environment coupling. Whether cognition is portable beyond Earth is therefore an open empirical question. Evidence from vestibular disruption, orbital adaptation, and terrestrial analogues indicates that altering this coupling can modify cognition and experience—yet cognition under long-duration decoupling from terrestrial conditions has never been instrumented as a distinct question. The gap is structural. A condition that has never varied offers no occasion for its own examination. Deep space is the first setting in which the environmental dependence of human cognition becomes empirically investigable, and the significance is not only practical. Constitutive claims formulated across a single environment become, once a second is available, hypotheses that discriminate. Mission success cannot itself establish cognitive viability; engineering achievement and the integrity of cognition are distinct. The article proposes a cognitive viability framework built on measures of coherence rather than performance alone, identifying a distinct object of inquiry: the conditions under which cognition remains viable beyond Earth—an ecology of deep space consciousness. Once that object is specified, its omission is no longer methodologically innocent.