[1] After leaving Yale University without defending his dissertation, he started his career in the early 1950s as a field geologist in Wyoming and Colorado working for the United States Geological Survey (USGS).

In the early 1960s, he moved to the Astrogeology division of the USGS and began working at NASA's Jet Propulsion Laboratory in Pasadena, California.

This included for the Apollo program, where, in the 1960s, he played a major role in choosing landing sites[3] and assisted in training astronauts in the basics of geology so they would know what to look for on the surface of the Moon.

[5] In 1985, Masursky was the recipient of the Distinguished Service Award, which is the highest honorary recognition an employee can receive within the Department of the Interior.

Quoting from the award, the 1985 USGS Yearbook states: “Harold Masursky, Geologist, for his imaginative leadership in the field of astrogeology which has influenced almost every facet of lunar and planetary exploration since the beginning of the nation's space program.”[6][7] The Masursky crater on Mars was chosen because it is effluvial, meaning "flow" (it looks like water ran through it), to honor his fervent belief that Mars once had flowing water on the surface.