21 years ago today, December 16th, 1992, NASA’s Galileo spacecraft took this image of Earth and the Moon from a distance of about 3.9 million miles (6.2 million km). It’s one of the few images ever captured that singularly show both worlds in their entirety.
And to think that when this image was taken, our planet’s human population was 5.49 billion — 1.7 billion less than it is today. To put that into perspective, it wasn’t until 1830 that Earth had 1 billion people living on it. The next billion wasn’t reached until 100 years later. (Source)
(Needless to say, Earth itself hasn’t gotten any larger.)
On December 16, 1992, the Galileo spacecraft looked back from a distance of about 3.9 million miles (6.2 million km) to capture this remarkable view of the Moon in orbit about Earth. The composite photograph was constructed from images taken through visible (violet, red) and near-infrared (1.0-micron) filters.
The Moon is in the foreground; its orbital path is from left to right. Brightly colored Earth contrasts strongly with the Moon, which reflects only about one-third as much sunlight as our world. To improve the visibility of both bodies, contrast and color have been computer enhanced.
At the bottom of Earth’s disk, Antarctica is visible through clouds. The Moon’s far side can also be seen. The shadowy indentation in the Moon’s dawn terminator–the boundary between its dark and lit sides–is the South Pole-Aitken Basin, one of the largest and oldest lunar impact features.
The trajectory which Galileo followed was called a VEEGA (Venus-Earth-Earth Gravity Assist), traveling first in toward the Sun for a gravity assist from Venus before encountering the Earth two times (spaced two years apart). These encounters with Venus and the Earth allowed Galileo to gain enough velocity to get it out to Jupiter, as well as study these two planets and the Moon.
Launched in October 1989, Galileo arrived at Jupiter in December 1995. After studying the giant planet and its family of moons, it ended its mission in 2003, impacting with Jupiter’s atmosphere.
Source: NASA History office