Almost all the pictures acquired by Mariner 10 that were used for mapping were obtained during the first encounter: those covering the southeast half of the quadrangle are incoming close-encounter images, and those covering the north-west corner are outgoing close-encounter images. At the time the pictures were obtained, the terminator was at about long 7 degrees to 8 degrees, within the eastern part of the quadrangle. A large gap in coverage between in the incoming and outgoing images appears as a northeast-trending diagonal blank strip on the base map. A small part of this gap was filled in the southwestern part of the quadrangle by very poor second-encounter images.