This image (FDS 108), acquired during the spacecraft's first encounter with Mercury, is located about 500 km east of the Caloris basin. The image shows hummocky plains interpreted as Caloris ejecta in the upper half of the picture and smooth plains in the lower half. Elongated hummocks and troughs aligned concentrically to the rim of the Caloris are well developed in the upper right part of the picture. A part of the pre-Caloris basin (240-km in diameter) seen in the lower part of the picture is filled with smooth plains. At the western margin of this basin is a west facing scarp that forms the boundary between hummocky plains (west) and smooth plains (east).
The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.