The piloted Mars sprint scenario of NASA's “Humans to Mars” initiative involves round-trip “sprints” with a 2-week exploration of the Martian surface. This paper investigates the bio-isolation dynamics of plants and humans in a piloted Mars sprint.To simulate a life support system for a crew of six, a transient, thermal-network model is used. Two crops, lettuce and winged beans, are chosen for a cabin greenhouse. The crew cabin and the greenhouse are physically separated but dynamically interfaced with mass and energy flows. The plants provide the bio-regenerative portion of air, water, food, and waste cycles. The percentage of contribution by bio-regeneration to air revitalization, water reclamation, wet food supply, and waste processing functions are 9, 29, 22, and 50 percent, respectively. The major conclusion of this study is that the bio-isolation requirements for a partially bio-regenerative life support system can be met with today's technology base, but the “garbage problem” continues to be challenging until alternate technologies are available for solid materials recycling in the space environment.