From the introduction: The players take the part of robotic probes sent back from the Mars colonies to determine what has happened on Earth. One participant acts as Game Master (GM) who presents the events of the mission to Earth and adjudicates the results of actions. The others (henceforth, simply players) each take the twin roles of one of the semi-disposable space probes sent to Earth and the team of investigators and engineers in Mars Mission Control, under the visionary guidance of Director Keeton, trying to keep the probe running and learn as much as they can, before the broken Earth's dangers beat it to scrap.