Caves and subsurface voids on Mars and other bodies can provide significant advantages when used for human habitat and operational space. They are also targets for significant scientific investigations. We have developed a suite of technology concepts to make utilization of extraterrestrial caves feasible. Our goal is to provide a solid foundation of information and options so that mission planners may realistically consider the subsurface option in development of mission scenarios. We have concentrated on identifying the primary challenges to human operation in the extraterrestrial cave environment. Employing concepts like inflatable cave liner habitats, foamed‐in‐place airlock technologies, and micro‐robotic self‐deploying communication, mapping, and data transmission networks, we are developing solutions to meet those challenges and demonstrate the feasibility of cave use on Mars. We present the results of field trials of an incave mission simulation in several Earth caves as a proof‐of‐concept demonstration. These trials during the summer and fall of 2003 culminate in a high fidelity simulation scheduled for January 2004. Concepts and prototypes were developed during a completed Phase I and on‐going Phase II NASA Institute for Advanced Concepts (NIAC) study.Caves and subsurface voids on Mars and other bodies can provide significant advantages when used for human habitat and operational space. They are also targets for significant scientific investigations. We have developed a suite of technology concepts to make utilization of extraterrestrial caves feasible. Our goal is to provide a solid foundation of information and options so that mission planners may realistically consider the subsurface option in development of mission scenarios. We have concentrated on identifying the primary challenges to human operation in the extraterrestrial cave environment. Employing concepts like inflatable cave liner habitats, foamed‐in‐place airlock technologies, and micro‐robotic self‐deploying communication, mapping, and data transmission networks, we are developing solutions to meet those challenges and demonstrate the feasibility of cave use on Mars. We present the results of field trials of an incave mission simulation in several Earth caves as a proof‐of‐concept demonst...