Fig A-1. Eighteen pictures, taken at 42-sec intervals by Mariner 10's two TV cameras, were computer-enhanced and assembled by hand into this photomosaic. The pictures were taken during a 13-min period when Mariner was 200000 km (124,000 mi) from Mercury on March 29 1974, and was rapidly approaching the planet. Latitude and longitude references for the figure are given in (a); (b) identifies some of the geological teatures. Kuiper was the first marking recognizable on the Mariner pictures taken during the approach to Mercury.