The Soviet probes sent to the planet Mars between 1960 and 1973, called the Mars series, provided meager results. The series was indefinitely suspended. Two basic types of craft were used, one weighing 1 ton and the other 5 times as much.The first series of launches began on Oct. 10 and 14, 1960, when two booster rockets failed during launch. The Mars 1 probe was successfully launched on Nov. 1, 1962, but two companion probes went off course soon after blastoff on October 24 and November 4. Mars 1 went dead long before it reached Mars. Contact was also lost en route with the Mars-bound Zond 2 probe launched Nov. 30, 1964.The second series of Mars probes used the larger Proton booster rocket. The first launch, in March 1969, blew up. Cosmos 419, launched May 10, 1971, appears to have been a Mars probe, but it failed to leave its parking orbit around the Earth. Mars 2 and Mars 3 were launched on May 19 and 28, 1971, and were inserted into orbit around Mars on Nov. 27 and Dec. 2, 1971, but entry probes dropped into the Martian atmosphere returned no data.A major expedition was mounted in 1973, the last opportunity prior to the scheduled American Viking probes in 1975. The great distance of Mars during this launch window imposed stiff payload penalties.
In order to send the equivalent of two orbiter/lander vehicles, the Soviets launched (May 19 and 28) two orbiters without landers (Mars 4 and 5) and subsequently (July 21 and 26) two lander probes with small control units (Mars 6 and 7). The two orbiters arrived on Feb. 10 and 12, 1974, but Mars 4 missed the planet by 2,100 km (1,300 mi) when its braking engine failed to operate. Mars 5 was successfully injected into Mars orbit, but its few television pictures were inferior in quality to those obtained by Mariner 9 in 1973. When the two landers Mars 6 and 7 arrived near Mars on March 12 and 9, respectively, one (Mars 7) missed the planet by 1,300 km (800 mi); the other entered the atmosphere but went dead during the final stages of the descent, after relaying some confusing atmospheric data on its way down.In 1988 the Soviet Union sent two probes toward Phobos, the larger martian moon. Both probes failed, one soon after launch and the other near Phobos.