Oblique view of the crater complex near Ascraeus Lacus in the Tharsis region of Mars was taken by Mariner 9. It is the northernmost of the prominent dark spots observed by Mariner during its approach to the planet. The spot consists of several intersecting shallow crater-like depressions. The main crater is approximately 21 kilometers (13 miles) across, the whole complex about 40 kilometers (25 miles) across. The crater probably is in a relatively high area of the Martian surface, which accounts for its being visible above the dust storm. The faint circular features outside the crater are probably atmospheric.
Mariner 9 was the first spacecraft to orbit another planet. The spacecraft was designed to continue the atmospheric studies begun by Mariners 6 and 7, and to map over 70% of the Martian surface from the lowest altitude (1500 kilometers [900 miles]) and at the highest resolutions (1 kilometer per pixel to 100 meters per pixel) of any previous Mars mission.
Mariner 9 was launched on May 30, 1971 and arrived on November 14, 1971.