Why Orrin's northern dunes are dark basalt that looks blue from orbit, how they creep a few metres a year, and how to walk them safely in a pressure suit.
Orrin's noon sky is butterscotch and its sunsets cold blue. Our science correspondent explains the dust behind it, where to watch near Corran and how to photograph it through a visor.
Four days and 38 km along the rim of the Gediz canyon, from Corran's dome past Bolívar Pass to the view of Mount Halvard. Suits, huts, air, water, packing and fitness, day by day.
