This Viking Orbiter 2 image shows a large dust storm over the Thaumasia region on Mars. This large disturbance soon grew into the first global dust storm observed by the Viking Orbiters. This image was taken at 9:00 local time near perihelion when heating of Mars is at a maximum. The image is at 1400 km across and north is at 1:00. (Viking Orbiter 176B02).