Canyon on Mars. Artwork of fog in the Noctis Labyrinthus canyon on Mars in the early morning. The fog forms when water ice on the canyon walls is vaporised by the rising Sun. High cirrus clouds create a halo (ring) around the Sun. On either side of the Sun are parhelia (sun dogs), bright spots caused by light refracting from high ice crystals. Noctis Labyrinthus is a canyon system that is a tributary of the vast Valles Marineris, the largest canyon in the solar system.