Viking 1 was launched on Aug. 20, 1975 and arrived at Mars on June 19, 1976. Viking 2 was launched Sept. 9, 1975 and entered Mars orbit on Aug. 7, 1976.

These tiny celestial bodies were discovered in 1877 by American astronomer Asaph Hall and are named after the sons of the Greek god Ares (the equivalent of the Roman god Mars): Phobos meaning ...