Today marks the 40th anniversary — July 20, 1976 — of the first U.S. robotic landing on another planet by the Viking 1 spacecraft on Mars.
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NASA spacecraft steers clear of Martian moon Phobos
NASA’s MAVEN spacecraft in orbit around Mars maneuvered out of the path of Phobos earlier this week after navigators predicted the spacecraft could run into the Martian moon in the near future, highlighting the challenge of tracking an international fleet of Mars probes set to double in size by 2021.