Quirks & Quarks·Analysis

NASA re-masters Carl Sagan's iconic 'Pale Blue Dot' image 30 years later

Bob McDonald's science blog

Bob McDonald's science blog

This updated version of the iconic "Pale Blue Dot" image taken by the Voyager 1 spacecraft uses modern image-processing software and techniques to revisit the well-known Voyager view while attempting to respect the original data and intent of those who planned the images. (NASA / JPL-Caltech)

NASA has re-mastered the "Pale Blue Dot" photo of the Earth taken by the Voyager 1 space probe from the outer edge of the solar system. The original image, and the vision it represents, was the brainchild of famous astronomer, Carl Sagan.

The Voyager mission was a remarkable journey through the solar system by twin spacecraft that flew past the giant planets Jupiter and Saturn, with Voyager 2 continuing out to Uranus and Neptune. Both spacecraft are now venturing into interstellar space where they will eventually drift among the stars for hundreds of millions of years.

A vision for a new perspective of Earth

In 1990, with the planetary encounters over, and no more images for the cameras to take, Dr. Sagan, who was a member of the imaging team, suggested that before the cameras on Voyager 1 were turned off, that they look back and take the first ever photo of the entire solar system as seen from the outer edge, a kind of family portrait.

At first, the idea was rejected by other scientists because running the cameras would use up precious energy and involve looking at the sun, which could damage the equipment. Besides, they would be nothing but dots from 6.4 billion kilometres away. But Sagan persisted and just before the cameras were shut down forever, a series of 60 images were taken to encompass the wide swath of sky that included most of the planets. (Mercury, Mars and Pluto were out of sight from that perspective.)

The cameras of Voyager 1 on Feb. 14, 1990, pointed back toward the sun and took a series of pictures of the sun and the planets, making the first ever "portrait" of our solar system as seen from the outside. (NASA / JPL)

Sure enough, they looked like dots, with the Earth taking up less than one pixel in its image. In fact, the image had to be enhanced to even see the Earth. 

It was the very smallness of that image that Carl Sagan used to turn it into an icon by calling it a "Pale Blue Dot," which also became the title of his 1994 book in which he says, "Look at that dot. That's here. That's home."

Earth and its place in our solar system

The "Pale Blue Dot" is one of a series of self portraits humanity has taken from space, each one farther and farther away. "Earthrise", taken by Bill Anders in 1968 aboard Apollo 8, was the first time humans saw our home planet rising above the horizon of an alien world. Later, in 1977, as Voyager 1 was just beginning its journey, it looked back to take the first photo of the Earth and moon together.

This photo of our planet from the moon, which was taken in 1968, was the first time humans saw our home planet rising above the horizon of an alien world. (NASA)

The Spirit rover on Mars spotted Earth above the Martian horizon just before sunrise, which was the first picture of ourselves taken from another planet. Later, the Cassini spacecraft in orbit around Saturn captured the Earth through the planets rings.

The only other spacecraft in a position to take an even more distant photo of Earth than Voyager is New Horizons, which flew past Pluto in 2015 and is continuing its journey deeper into the Kuiper belt. But we will have to wait years until the mission is over, and by that time the craft will be so far away the Earth could entirely lost in the glare of the sun. 

This is the first image ever taken of Earth from the surface of a planet beyond the Moon. It was taken by the Mars Exploration Rover Spirit one hour before sunrise. (NASA / JPL / Cornell / Texas A&M)

Finding meaning in these new perspectives

As an astronomer and visionary, Carl Sagan had a perspective of the Earth as a small planet, which he tried to convey through his teachings, books and television programs. And thanks to his efforts on the Voyager team, we got to actually see our home from afar and appreciate how small it really is.

From a great distance, we appear as a tiny blue oasis of life in a vast and violent universe. Political boundaries drawn on that dot cannot be seen, and all the conflicts we humans engage in seem insignificant when played out on such a small speck. The other dots in the Voyager mosaic are inhospitable worlds. Earth is the only planet in our solar system where humans can walk outside without wearing a spacesuit.

 As Dr. Sagan said, take a moment and just look at that dot.

In this rare image taken on July 19, 2013, the wide-angle camera on NASA's Cassini spacecraft has captured Saturn's rings and our planet Earth and its moon in the same frame. Earth, which is 1.44 billion kilometers away in this image, appears as a blue dot at center right; the moon can be seen as a fainter protrusion off its right side. (NASA / JPL-Caltech / Space Science Institute)

About the Author

Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC-TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.