Our mysterious neighbour

Viking Orbiter colour mosaic of Mars, showing the Valles Marineris canyon system (centre) and three of the large shield volcanoes along the western (left) limb.
(Picture credit: NASA/JPL)

Viking Orbiter colour mosaic of Mars, showing the Valles Marineris canyon system (centre) and three of the large shield volcanoes along the western (left) limb.
(Picture credit: NASA/JPL)