OTD…Jan. 28 and STS-51L

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 1994…Endeavour experienced an on-pad abort due to a main engine problem during startup

#OTD in 1998…The launch of Discovery on final shuttle-Mir docking mission