Mars - Spacecraft, Exploration, Missions: Since the beginning of the space age, Mars has been a focus of planetary exploration for three main reasons: (1) it is the most Earth-like of the planets; (2) other than Earth, it is the planet most likely to have developed indigenous life; and (3) it will probably be the first extraterrestrial planet to be visited by humans. Between 1960 and 1980 the exploration of Mars was a major objective of both the U.S. and Soviet space programs. U.S. spacecraft successfully flew by Mars (Mariners 4, 6, and 7), orbited the planet (Mariner 9 and Vikings 1 and 2), and
Mars - Spacecraft, Exploration, Missions: Since the beginning of the space age, Mars has been a focus of planetary exploration for three main reasons: (1) it is the most Earth-like of the planets; (2) other than Earth, it is the planet most likely to have developed indigenous life; and (3) it will probably be the first extraterrestrial planet to be visited by humans. Between 1960 and 1980 the exploration of Mars was a major objective of both the U.S. and Soviet space programs. U.S. spacecraft successfully flew by Mars (Mariners 4, 6, and 7), orbited the planet (Mariner 9 and Vikings 1 and 2), and