Harold Masursky, 66, a pioneer space scientist who was involved in the Mercury and Apollo programs and the Viking experiments on Mars, died Aug. 24 at his home in Flagstaff, Ariz. He had diabetes.

He retired in February after 43 years with the U.S. Geological Survey. He was a former chief of the U.S. Geological Survey's astrogeology center and a leading geologist in the fields of planetary and lunar exploration. He joined the center in 1963 as its chief scientist.

He directed the team that mapped Mars. In 1976, the team's maps were used in selecting the landing site for the Viking flight to Mars. He also had helped set up Viking's experiments.

In the 1980s, he had a major role in founding the Magellan space project. It is now involved in mapping Venus. He also had been active in the Voyager project to explore and map the outer planets of the solar system.

Mr. Masursky also had presided over the international Working Group on Planetary System Nomenclature. The 10-nation group is charged with naming new heavenly bodies. He had been involved in naming new astronomical discoveries for over 20 years.

He was a member of 41 scientific groups and received four awards of excellence from the Geological Survey. His other awards included the Smithsonian Institution's National Air and Space Museum Award for Achievement in Lunar and Planetary Exploration, which he received in 1988.

Mr. Masursky was born in Fort Wayne, Ind., and graduated from Yale University. He joined the USGS in 1947 and explored the western United States for fossil fuels before transferring to the astrogeology branch in 1962. He had worked for the USGS in Colorado and California before coming here.

Survivors include his wife; four children; two grandchildren; and three sisters.