Borealis Quadrangle - Mariner 10 Images

Mariner 10 Images

In the Borealis region, Mariner 10 images are available for only the western hemisphere, from long 0° to about long 190° W. Mercury was in darkness beyond long 190° W. on March 29, 1974, when the first Mariner 10 flyby acquired the most useful photographs of the region. Most of the photographs used for geologic mapping were acquired by the departing spacecraft during the first pass (Mercury I). The Mercury II encounter provided no usable images of the map area; two low-oblique photographs suitable for geologic mapping were acquired during the third flyby on March 17, 1975. No stereoscopic photographic pairs are available for the Borealis region.

Because the terminator was a few degrees away from the 0°-180° meridian at the time of the first encounter, photographs of the region were acquired under a wide range of lighting conditions. These conditions and the large obliquity of the photographs hampered geologic interpretation of surface materials in the map area, as they did in the Kuiper (De Hon and others, 1981), Victoria (McGill and King, 1983), and Shakespeare (Guest and Greeley, 1983) quadrangles to the south.