On Aug. 23, 1966, this landmark photo was transmitted to Earth by NASA's unmanned Lunar Orbiter I -- a robotic surveyor sent into orbit to map possible lunar landing sites years before the Apollo program -- and was received at a NASA tracking station near Madrid, Spain.
This view of the Earth's crest over the lunar horizon was taken during the Apollo 15 lunar landing mission.
Astronaut Harrison Hagan Schmitt stands next to an American flag seemingly pointing to Earth in the far distance -- a beacon of life in the void -- during Apollo 17's December, 1972 mission to the moon. The clean, white perfection of Schmitt's space suit; the rumpled flag; the black of space; the hint of blue Earth -- if one wanted to compose a tableau that said "space exploration," it might look a lot like this.
Astronaut Ed White makes the first American space walk -- if one can call traveling at around five miles per second, 120 miles above the Pacific Ocean, a "walk" -- on June 3, 1965.
Gemini 11 photographs India and Ceylon (now Sri Lanka).
The Apollo 9 mission, launched shortly before the Apollo 11 mission to the moon, tested critical devices like the Lunar Module, which, a mere four months later, landed Neil Armstrong and Buzz Aldrin on the moon. This photograph has an appealing air of unreality about it: How can anything that enormous (see the open hatch door for scale) actually appear to float?
Voyager 1 recorded the first picture of a crescent-shaped Earth and Moon -- the first of its kind ever taken by a spacecraft -- on September 18, 1977.
In a photograph taken from the space shuttle Columbia that's astonishing for its clarity and breathtaking beauty, Chile and the Andes mountains look close enough to touch, while the perfect blue curve of the Earth's atmosphere against the black void of space looks at once incredibly fragile and eternal.
Forty-five years ago, humanity welcomed its first view of Earth taken by a spacecraft from the vicinity of the Moon. In celebration of this landmark transmission, we present other remarkable, moving, humbling photos of our lonely blue and green planet taken from the depths of space. See the full slideshow at LIFE.com.