The fossae are the linear troughs that are seen running approximately diagonal across the scene from upper right toward lower left. The fossae are a series of horsts and graben formed by faulting of the upper martian crust. Graben are the down-dropped trough floors, horsts are the uplifted, relatively flat areas between the troughs. The base map is a U.S. Geological Survey photomosaic of Viking Orbiter images with a scale of 64 pixels per degree of longitude. Most of the mosaic images are illuminated from the right.
North is up.
This is a portion of Viking 1 Orbiter image 627a28, taken in 1978. The Viking image is presented here as a mercator projection with a scale of 1100 pixels per degree of longitude. The regularly-spaced lineations in the troughs in the lower third of the image are drifts of windblown material. Sun illumination is from the left. North is up.