Learn about NASA's Viking Missions to Mars 1975 - 1977 in this educational video from dizzo95.
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Male Speaker: In 1975, two Viking spacecraft were launched, each of which was programmed to land a robot on the Martian surface. One of its principle objectives was to test for the presence or absence of living organisms. On June 19, 1976, the first Viking arrived in the vicinity of Mars after a year long journey of more than 400 million miles. Once in orbit, its cameras were turned to a detailed examination of the landing area. Imaging teams on earth scanned some 800 photographs covering a territory of about the size of Texas. The chosen landing site was a bad experience for the few in that craters, one of the lowest regions on the surface. On July 20, 1976, flight controllers ordered the lander to separate from the orbiter -- great distance from earth, a signal traveling at the speed of light 186,000 miles per second took 19 minutes to reach the spacecraft. This necessated a completely automated system on board by carrying out the landing -- during the Lander's descent, its instruments analyzed the properties of the thin Martian atmosphere.