The Marineris canyon floors generally run down west to east. In Candor, they curved around the great central mesa, then fell precipitously south into Melas. Snow lay on the higher parts of the floor, especially under the western walls where shadows lay in the afternoon. Meltwater from this snow ran down in a faint tracery of new watersheds, made up of sandy braided streambeds that ran together into a few shallow muddy red rivers, which collected at a confluence just above the Candor Gap, and poured down in a wild foaming rapids to the floor of Melas Chasma, where it pooled against the remnant of the 61 glacier, running redly against its northern flank.

On the banks of all these opaque red streams, forest galleries were springing up. They consisted in most places of cold-hardened balsas and other very rapidly growing tropical trees, creating new canopies over older krummholz. These days it was warm on the canyon floor, which was like a big sun-reflecting bowl, protected from the wind. The balsa canopies were allowing a great number of plant and animal species to flourish underneath them; Nirgal’s acquaintances said it was the most diverse biotic community on Mars. They had to carry sedative dart guns now when they landed and walked around, because of bears, snow leopards, and other predators. Walking through some of the galleries was becoming difficult because of thickets of snow bamboo and aspen.