Red Mars starts in 2026 with the first colonial voyage to Mars aboard the Ares, the largest interplanetary spacecraft ever built and home to a crew who are to be the first hundred Martian colonists. The ship was built from clustered space shuttle external fuel tanks which, instead of reentering Earth's atmosphere, had been boosted into orbit until enough had been amassed to build the ship. The mission is a joint American–Russian undertaking, and seventy of the First Hundred are drawn from these countries (except, for example, Michel Duval, a French psychologist assigned to observe their behavior). The book details the trip out, construction of the first settlement on Mars (eventually called Underhill) by Russian engineer Nadia Cherneshevsky, as well as establishing colonies on Mars' hollowed out asteroid-moon Phobos, the ever-changing relationships between the colonists, debates among the colonists regarding both the terraforming of the planet and its future relationship to Earth. The two extreme views on terraforming are personified by Saxifrage "Sax" Russell, who believes their very presence on the planet means some level of terraforming has already begun and that it is humanity's obligation to spread life as it is the most scarce thing in the known universe, and Ann Clayborne, who stakes out the position that humankind does not have the right to change entire planets at their will.