Space crews venturing beyond low Earth orbit will experience unprecedented levels of autonomy and unpredictable challenges. Mission success will require effective teamwork. How do teamwork capabilities change over time in isolation and confinement? To explore this question, we observed the 4, 4-member crews who participated in the 30-day campaign of NASA's Human Exploration Research Analog (HERA). Crews endured isolation, confinement, and communication delays. We tracked teamwork capabilities along three critical dimensions: generate (creativity tasks), choose (problem solving tasks), and negotiate (ethical decision-making tasks). To assess these capabilities, we administered a battery of three tasks, one requiring the crew “generateâ€, one to “chooseâ€, and one to “negotiate.†Team task batteries were performed on Mission Days 11, 16, and 30. Results indicated that crew performance declined over time; however, there were differences across team performance dimensions. All 4 crews showed declining abilities to “generate†and to “choose.†However, though the 4 crews differed in their ability to “negotiate,†their capacity was relatively stable during the mission. We consider the implications of these results for the design of countermeasures that support crew functioning.