Dixon remembered when images from the Viking 1 mission — the first to land on Mars — began streaming back to Earth in 1976.
NASA released a quickly colorized image of rust-colored dirt and a blue sky — much as Dixon had depicted in his paintings.
"Everybody assumed Mars had a thin atmosphere, so it would look like our stratosphere — a beautiful cerulean blue," he said.
But within a few days, NASA released another image — this time after the cameras had been properly calibrated, showing the true colors of the sky. "It was the strangest salmon pink," he said.
Viking 1 was only the first of many revelations.
When Voyager 1 passed Jupiter in 1979, it snapped pictures of the moons Io and Europa, which artists had usually painted as bare rocks in space. In the new images, Io looked red-hot, mottled with dark circles of volcanic activity. Europa had an icy, pale peach-colored surface, crossed by long, dark crevasses.
"They turned out to be much more exotic than anybody imagined," Dixon said.
In 1990, the first images from Hubble were released. It was as if astronomy had entered the Psychedelic Age — stunning blues, pinks and yellows exploded through the universe.
Some of the colors were the product of researchers artificially colorizing the invisible spectrum of light, but it didn't matter to viewers. Distant galaxies and supernovae became postcards and computer wallpaper.
Dixon has since labeled about 70% of his paintings "dated concepts," though he still displays them on his website.
LuAnn Williams Belter, Astronomy magazine's art director, said that when there is a choice today between an illustration and a photograph, the photograph usually wins.
Over the last 15 to 20 years, the number of space paintings in the magazine has dropped by about half, said Rich Talcott, a senior editor.
"If space art's identity is to take us where we can't go ourselves, there are fewer areas where that is true," he said.
