Terra region of Mars. The landed mass was 635 kg. The descent module transmitted 224 seconds of data before transmissions ceased, the first data returned from the atmosphere of Mars. Much of the data was unreadable due to a flaw in a transistor which led to degradation of the system during its journey to Mars. Mars 7 Mars 7 successfully lifted off on August 9, 1973, into an intermediate Earth orbit on a Proton-K/D booster and then launched into a Mars transfer trajectory. Total fueled launch mass of the lander and bus was 3260 kg. It reached Mars on March 9, 1974. Due to a problem in the operation of one of the on-board systems (attitude control or retro-rockets) the landing probe separated prematurely (4 hours before encounter) and missed the planet by 1300 km. The early separation was probably due to a computer error which resulted from degradation of the systems during the trip to Mars. The intended landing site was . The lander and bus continued on into heliocentric orbits. Mars 4NM and 5NM The Mars 4NM and Mars 5NM projects would have seen heavier spacecraft launched by N1 rockets. They would have deployed heavy Marsokhod rovers onto the surface, and conducted sample return missions. The N1 failed on all four of its test flights, and was never used to launch any Mars spacecraft. Mars 5M Mars 5M (Mars 79) was a sample return mission developed in 1977 to be double launched in 1979 by Proton launchers and then docked in Earth orbit for a joint flight of orbital and return modules to Mars. The project was canceled due to the low reliability of the Igla automatic docking system. See also Exploration of Mars Space exploration Robotic spacecraft References External links NSSDC Mars 5 page catalog of Soviet Mars images NASA's mars probe website Mars Series (USSR) Profile by NASA's Solar System Exploration Ted Stryk's page on the Mars 4-7 probes TASS notice on the Mars-3 landing (in Russian) (Wikisource) "The Rocky Soviet Road to Mars" by Larry Klaes - EJASA October, 1989 "The Difficult Road to Mars" By V. G. Perminov