Carl Sagan asked Voyager to photograph the Pale Blue Dot

Person: Carl Sagan
Lived: 1934–1996
Field: Astronomy, planetary science
From: American

The story

Voyager 1 was launched on September 5, 1977, to study the outer solar system. After flying past Jupiter in 1979 and Saturn in 1980 it completed its primary mission and headed out of the solar system. Carl Sagan, who had been an experimenter on the Voyager missions, saw a final opportunity. When the spacecraft passed Saturn in 1980 he proposed that it turn around and take one last picture of Earth.

He acknowledged that the image would have little scientific value, since Earth would be far too small for the cameras to show any detail, but he argued it would offer a priceless perspective on humanity's place in the universe. Many people in the Voyager programme liked the idea, and the planetary scientist Carolyn Porco had independently proposed something similar. There were worries that pointing the cameras so close to the Sun might damage them, and the plan was delayed for years until NASA Administrator Richard Truly stepped in to make sure it happened.

On February 14, 1990, as part of a family portrait of the solar system, Voyager 1 photographed Earth from a distance of about 6 billion kilometres, roughly 40 times the distance between Earth and the Sun. Porco and Candy Hansen of the Jet Propulsion Laboratory designed the commands and exposure times. The images were sent home between March and May 1990, and three frames taken through different colour filters were combined to make the final picture. In it our planet occupies less than a single pixel, a pale speck caught in a band of scattered sunlight. Its blue tint comes mainly from the same scattering of sunlight that makes the sky look blue.

Sagan named the image the Pale Blue Dot and made it the centrepiece of his 1994 book Pale Blue Dot: A Vision of the Human Future in Space. He reflected that everyone who has ever lived did so on that mote of dust suspended in a sunbeam, and that the image underlined our responsibility to deal more kindly with one another and to cherish the only home we have ever known.

NASA has marked the photograph's anniversaries, and in 2020 it released Pale Blue Dot Revisited, a version reprocessed with modern techniques. In 2022 Sagan's audiobook of Pale Blue Dot was added to the Library of Congress National Recording Registry.

Why it matters

The Pale Blue Dot became one of the most famous images ever made, a lasting reminder of Earth's smallness and fragility that still shapes how people think about caring for the planet.

About Carl Sagan

Brooklyn-born astronomer who explained the Venus greenhouse, helped send humanity’s messages on Pioneer and Voyager, and taught Cosmos viewers worldwide to look at the universe with wonder and doubt.

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Carl Sagan

1934–1996 · Astronomy, planetary science

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