OTD…Sept. 20 and Endeavour retirement

The last space shuttle external tank in existence, headed from the New Orleans manufacturing plant to the California Science Center for the vertical launch pad display of the retired orbiter Endeavour, has passed through the Panama Canal.

#OTD in 1985…Discovery launched on the first classified space shuttle mission for the Department of Defense. Watch the liftoff:

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.