NASA’s Voyager spacecraft captured one of the most memorable images in the history of space exploration 25 years ago today.
On Feb. 14, 1990, the Voyager 1 spacecraft was commanded by NASA at the suggestion of Carl Sagan to turn its camera around and take a picture of Earth one last time before it headed on its way out of the solar system. The photo is now widely recognized as the “Pale Blue Dot.”
Captured from beyond the orbit of Neptune at some 3.7 billion miles from the sun, or 40 times the distance between the Earth and the sun, the photo shows Earth as no more than a pixel caught in a scattered light ray, an effect caused by taking a photo so close to the sun.
The image was one of a series of photos of our solar system captured by Voyager 1 showing the sun and the planets at a distance of almost 4 billion miles away. The “Family Portrait,” as NASA calls it, shows all the planets in the solar system except for Mercury, which was too close to the sun to be seen, and Mars, which was obscured by light from the sun. Pluto, which at the time was considered a planet, was too dim to be detected.
Having already completed its prime mission, the photos that comprise Voyager 1′s “Family Portrait” were the last to be taken by the spacecraft. The camera was disabled to save power and memory for use by other scientific instruments on the spacecraft.
The images were not originally planned as part of the mission, but Carl Sagan, a member of the Voyager imaging team, suggested the spacecraft capture one last image of Earth before embarking on its interstellar mission. He thought it might offer perspective on humanity’s place in the universe. Sagan later expounded upon the significance of the image in a passage of his book, Pale Blue Dot: A Vision of the Human Future in Space.
“That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives,” Sagan wrote in his book. “There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”
The image is so powerful that it has inspired others to capture images of Earth from the outer solar system. Most famously, Carolyn Porco, an astronomer in the vein of Sagan who heads the Cassini imaging team, reprised the popular photograph captured from orbit around Saturn.
The new image of Earth, dubbed “The Day the Earth Smiled,” was captured by NASA’s Cassini spacecraft on July 19, 2013 at a distance of approximately 900 million miles, as part of a larger mosaic of the Saturn system. “The Day The Earth Smiled” was only the third time that the Earth has been photographed from the outer solar system and the first time that people on Earth knew in advance that such a photo of their planet was being taken.
Photographs of Earth from the outer solar system are uncommon because the sun’s powerful rays interfere with a spacecraft’s cameras. Cassini was able to capture this rare photo of Earth while Saturn eclipsed the sun, protecting its camera from the potentially damaging rays and providing a unique photo opportunity. Cassini captured a similar image of Earth as seen from behind Saturn in 2006.
Today, Voyager 1 has traveled further into space than any other man-made object and it became the first spacecraft to enter interstellar space in 2012. Launched on Sept. 5, 1977, the spacecraft has operated for more than 37 years providing a wealth of scientific information on previously unexplored regions of the solar system. The spacecraft is expected to continue operating for at least another 10 years, until its thermoelectric generators run out of power.
Voyager 1 is more than three times farther away from Earth than it was 25 years ago, 130 times the distance between the Earth and the sun. If Voyager were to capture an image of Earth today, it would be 10 times dimmer than it appears in the “Pale Blue Dot.”