OTD…July 29 and STS-51F

#OTD in 1982…Columbia launches on the fourth space shuttle mission. #OTD in 1995…Atlantis launches on first shuttle-Mir docking flight

#OTD in 1992…Columbia launches on the first Extended Duration Orbiter mission

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.