In Greek mythology, Antaeus was a giant encountered by Hercules. A mighty wrestler, Antaeus forced passing strangers to wrestle with him and lolled them when he won. The Earth was his source of superhuman power, and as long as he could touch the ground he was invincible. If an opponent threw him down, he sprang back with renewed vigor from his contact with the Earth. Hercules was able to defeat Antaeus by holding him in the air and strangling him.Participants in the NASA-ASEE Engineering Systems Design Summer Program studied the feasibility of establishing an orbiting quarantine facility where samples returned from Mars could be analyzed. The particular advantage in this approach is that any pathogens the samples might contain would be less likely to pose a hazard to Earth. Like Antaeus, for whom the project is named, such an organism might thrive on contact with the terrestrial biosphere. By keeping the pathogen contained and distant, the proposed orbiting quarantine facility would safeguard the Earth from possible contamination.On several occasions, both before and after the two unmanned Viking spacecraft successfully landed on Mars and carried out their extensive suite of experiments, NASA conducted studies aimed at defining mission requirements for the unmanned return to Earth of Martian soil samples. All aspects of such a Mars sample return (MSR) mission were considered, including mission profile, vehicle design, flight trajectories, scientific analysis of the returned samples, and planetary quarantine or planetary protection (PP) factors. During the course of these studies it became clear that PP factors could have a significant impact on mission design, cost, and complexity, depending upon how serious a concern they were judged to represent and what means were proposed to handle them during the course of the MSR mission. Planetary protection factors of interest in this context related mainly to the issue of back contamination-that is, the possibility of contamination of the Earth's biosphere by potentially hazardous microbes which could be present in the Martian soil samples. Even after the Viking missions did not detect life in the samples analyzed, there were many scientists who felt that any samples returned from Mars should be held in strict isolation until analyses could be performed to show that the soil was free of hazardous species. As part of these MSR mission design studies, related studies were earned out to find solutions to the potential back-contamination problem. Options studied ranged from the extreme proposal of sterilizing the sample in transit, before it reached the vicinity of the Earth, to simply housing the sample in a special Earth laboratory similar to the Lunar Receiving Laboratory. Consideration was also given to isolating the sample in a maximum containment facility like those used for highly infectious diseases or recombinant DNA research. Yet another report proposed that the best solution was to isolate and analyze the sample in an Earth-orbiting laboratory before certifying it safe for release to terrestrial laboratories.