OTD…Sept. 7 and STS-69

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.

#OTD in 2006…A star-spangled start to Discovery’s STS-121 mission

#OTD in 2001…Atlantis launched the Quest airlock module to the International Space Station