For twelve days in April 2002 we performed a closed simulation in the Mars Desert Research Station in Utah, isolated from other people, while exploring the area and sharing daily chores. Email provided our only means of contact; all mission-related messages were mediated by a remote mission support team. This protocol enabled a systematic and controlled study of crew activities, scheduling, and use of space. The study was primarily a methodological experiment in participant observation and work practice analysis, gathering quantitative data as part of an ethnographic study. The work practice analysis focused on two questions: Where did the time go-why did the crew feel rushed and unable to complete their work? How can we measure productivity, to compare habitat designs, schedules, roles, and tools? Analysis suggests that a simple scheduling change-having lunch and dinner earlier, plus eliminating afternoon meetings-increased the available productive time by 41%. Furthermore, observation of work practices suggested how to eliminate direct use of GPS devices by the crew, illustrating how an ethnographic study can help produce dramatically new operations concepts.