WASHINGTON, July 20 (UPI) -- Astronauts aboard the International Space Station Monday celebrated the 40th anniversary of Neil Armstrong and Buzz Aldrin's historic moon walk, NASA said.

WASHINGTON, July 20 (UPI) -- The United States should send humans to Mars, not back to the moon, the crew of Apollo 11 said in a rare joint appearance in Washington.

Neil Armstrong and Buzz Aldrin took the first steps on the moon 40 years ago, topping off one of the greatest feats of mankind.

WASHINGTON, July 17 (UPI) -- Neil Armstrong's left boot hit moon dust at 10.56 p.m. EDT on Sunday, July 20, 40 years ago. He then uttered the immortal words, "That's one small step for man, one giant leap for mankind."

HOUSTON, July 17 (UPI) -- SPACE CENTER, Houston, June 20, 1969 (UPI) -- Man reached the moon Sunday at 4:17:45 p.m. EDT. Then, for the first time, he set his foot on the soil of an alien world.

SPACE CENTER, HOUSTON, July 20, 1969 (UPI) -- Man reached the moon Sunday at 4:17.42 p.m. (EDT).

SPACE CENTER, HOUSTON, July 19, 1969 (UPI) -- Apollo 11 dropped into orbit around the moon today and started scouting the landscape where man will take his first steps late Sunday or early Monday.

SPACE CENTER, Houston, July 19, 1969 (UPI) -- America's flawless Apollo 11 whipped around the dark side of the moon Saturday and fired a 6-minute rocket blast that hung it in lunar orbit -- setting the stage for man's first landing Sunday in a world other than his own.

CAPE KENNEDY, Fla., July 16, 1969 (UPI) -- Apollo 11, carrying three astronauts and the dreams of humanity, blasted away for the moon today on a historic voyage to place the footprints of man in the dust of an alien world.