THEMIS Image of the Day, July 5, 2016. This VIS image shows part of Tractus Catena, just one of many north/south trending tectonic graben located south of Alba Mons. The features running vertically in the image are part of Tractus Catena. While other graben in the area are identified as fossae (defined as a long, narrow depression), the circular depressions within this graben lead to the descriptor name catena (defined as a chain of craters). In this case the craters are a result of roof collapse into an underlying open space such as a lava tube. Cross cutting and perpendicular to Tractus Catena is a younger graben.
More THEMIS Images of the Day by geological topic.