It is somewhat fitting that two of the most iconic space exploration images were taken by the first and last manned missions to leave Earth's orbit. Like its complement, Earthrise, The Blue Marble has been widely reprinted in magazines, textbooks, and motivational posters. It was taken by the crew of Apollo 17, the final Apollo lunar mission, and, as is customary for NASA, is credited to all three astronauts. The photograph is unique in that it shows the Earth fully lit rather than the more common crescent shape demonstrated in Earthrise. Interestingly, it was taken 'upside-down' with Antarctica at the top of the image and the Mediterranean Sea at the bottom. This was later changed by NASA in its reprints to conform with the conventional North-South orientation of the continents. Because of the fame of the photo it has become a synecdoche for an entire class of photographs with various images since being given the same title.
Aside from the photo itself, a fair amount of history goes into how Apollo 17 became the final lunar mission and came to be in the position to capture such a photograph. Following the successful moon landings of Apollo 11 and 12 and the apparent end of the Space Race in an American victory, both the American public and government began to lose the stomach for the substantial funding of NASA which at the time represented 5% of the national budget. Inevitably there were budget cuts and reprioritizations. In January 1970, less than six months after the first moon landing, NASA announced that it was canceling the Apollo 20 mission in order to free up funding as well as a rocket for Skylab, the first of several planned Apollo Applications missions. Originally, NASA had budgeted for the construction of 15 Saturn V rockets, two unmanned missions and thirteen manned missions including ten lunar landings (Apollo 11-20).
The catastrophic malfunction of Apollo 13 in April 1970 underscored the dangers of manned space flight and increasingly brought into doubt the benefits of continued moon missions. In September 1970, NASA canceled two additional missions which were at the time Apollo 15 and Apollo 19. The subsequent renumbering of missions meant that the new Apollo 15 (previously Apollo 16) would become a 'Type J' mission; a longer lunar stay with a lunar rover rather than the originally planned 'Type H' mission with two moon walks. These cancelations were also part of freeing up funding for an Applications mission, this time the Apollo Soyuz Test Project colloquially referred to as Apollo 18.
After the ASTP in 1975, funding for NASA was reduced even further and NASA turned its attention back to unmanned probes, launching the famous Pioneer 10 (1972), Viking (1975), and Voyager (1977) missions. Arguably none of the photos taken by these probes ever became quite so famous as The Blue Marble (though Pale Blue Dot gets an honorable mention). The idea that the photo was taken by a pair of human hands imbues it with an unshakable sense of wonder that a robotic eye can't ever hope to match.