Mariner 10 Photography
About half of the region was beyond the terminator during the three Mariner 10 encounters and hence not visible. The entire mapped area was covered by near-vertical photography from the second encounter, and the eastern part, from longitude 15° to about 110°, was covered by oblique photography from the first encounter. No third-encounter images were acquired. The entire visible area may be viewed stereoscopically by combining images from the first and second encounters taken at different viewing angles or by combining second-encounter images of the same area taken at different viewing angles. These combinations provided excellent qualitative control of topographic relief and a good quantitative photogrammetric base. However, sun-elevation angles of the images are limited to less than 25°, and image resolutions are no higher than about 0.5 km per picture element. Therefore, the south polar geologic map reflects mostly large-scale processes and topographic information, whereas other mercurian quadrangle maps benefit from greater albedo discrimination and, in some cases, higher resolution.
The imaged part of the Bach region covers about 1,570,000 km2. Its surface consists of craters of a wide variety of sizes and morphologies, as well as plains units, fault scarps, and ridges. It includes three double-ring basins that range from 140 to 200 km in diameter: Bach (after which the region is named), Cervantes, and Bernini. Another large crater, Pushkin, is 240 km in diameter and occurs at the map boundary at latitude 65° S., longitude 25° . Both Bach and Bernini display extensive fields of secondary craters. An unusual area between lat 69° and 80° S. and long 30° and 60° consists of young, relatively smooth plains marked by many flat-topped ridges unlike any seen in other areas of Mercury. Scarps similar to Discovery Rupes (in the Discovery quadrangle adjacent to the north) are relatively common throughout the Bach region. The most common terrain units in the region are the plains units, which display a wide range of small-crater densities.
Read more about this topic: Bach Quadrangle
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