On July 20, 1976, Viking 1 became the first American spacecraft to land safely on Mars and return a picture from the surface, an achievement marking its 50th anniversary this year. It was not easy to get there safely. Two scientists involved in selecting that touchdown site, Harold Masursky and Norman Crabill, later explained in a paper titled ‘The Viking Landing Sites: Selection and Certification’ published in Science that the original landing zone was abandoned just days before landing, over safety concerns. The last-minute scramble helped establish a process that NASA still uses today whenever it selects a landing site on Mars.
A photo that changed how we saw Mars
