Soviet Mars Program

The Soviet Mars program pursued robotic flyby, orbital and landing investigations through missions launched from 1960 to 1973, with the final encounters taking place in 1974. Early spacecraft tested the difficult chain from launch and interplanetary navigation to long-distance communications; many were lost before reaching Mars. Later generations carried increasingly ambitious remote-sensing instruments and separate descent vehicles. Mars 2 and 3 returned orbital observations in 1971–1972, although their landing experiments did not establish sustained surface science. The 1973 campaign divided tasks between the Mars 4 and 5 orbiters and the Mars 6 and 7 flyby-and-lander missions. Their outcomes ranged from a short orbital survey and atmospheric descent measurements to missed encounters and failed landings. These partial returns and engineering failures form an important foundation of early planetary exploration.