The Borealis quadrangle is a quadrangle on Mercury surrounding the north pole down to 65° latitude. It was mapped in its entirety by the MESSENGER spacecraft, which orbited the planet from 2008 to 2015, excluding areas of permanent shadow near the north pole. Only approximately 25% of the quadrangle was imaged by the Mariner 10 spacecraft during its flybys in 1974 and 1975. The quadrangle is now called H-1. It contains the Goethe Basin, whose diameter of at least makes it the sixth-largest impact basin observed on Mariner 10 images(Murray and others, 1974; Boyce and Grolier, 1977; Strom, 1977). The west half of the mapped area (between long 100° and 190° W.) is dominated by older craters and by intercrater plains material that lies between and within them. Younger crater materials, intermediate plains material, and small patches of smooth plains material are superposed on all other units. The crater Verdi, in diameter, is the largest of the younger craters. Its extensive ejecta blanket and secondary crater field are superposed on plains materials and older craters. The east half of the mapped area (between long 0° and 100° W.) is characterized by smooth plains material (Murray and others, 1974). This unit covers vast expanses of Borealis Planitia, a depression about in diameter that has an irregular arcuate west boundary. This depression is located over the site(s) of one or several old impact structures (Boyce and Grolier, 1977). Adjacent quadrangles to the south of Borealis are Victoria quadrangle (0° to 90° W), Shakespeare quadrangle (90° to 180° W), Raditladi quadrangle (180° to 270° W), and Hokusai quadrangle (270° to 0° W). It is opposite the Bach quadrangle at the south pole. 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°