MELISSA BLOCK, host:
This week marks the 20th anniversary of a photograph. It's a dramatic shot, even if, at first glance, it seems like a dark picture of nothing at all. But if you look closely, you can see a tiny speck of light. That speck is the Earth seen from very, very, very far away. NPR's Nell Greenfieldboyce has the story of that famous image, known as the pale blue dot.
NELL GREENFIELDBOYCE: Twenty years ago, Candice Hansen-Koharcheck was sitting in front of a computer at NASA's Jet Propulsion Lab in California.
Ms.�CANDICE HANSEN-KOHARCHECK (NASA): I was all alone, actually, that afternoon, in my office.
GREENFIELDBOYCE: Her office was dark. The window shades were drawn. She was searching through a database of images sent home by a distant spacecraft
Ms.�HANSEN-KOHARCHECK: I knew the data was coming back, and I wanted to see how it had turned out.
GREENFIELDBOYCE: Finally, she found it.
Ms.�HANSEN-KOHARCHECK: It was just a little dot, about two pixels big, three pixels big, so not very large.
GREENFIELDBOYCE: It was the Earth, seen by the Voyager 1 probe, which at the time was nearly four billion miles away. Because of an accidental reflection off the spacecraft, the tiny speck seemed to be lit up by a glowing beam of light.
Ms.�HANSEN-KOHARCHECK: You know, I still get chills down my back because here was our planet, bathed in this ray of light, and it just looked incredibly special.
GREENFIELDBOYCE: Special, and yet, if you weren't searching for it, it would be almost invisible. The Apollo astronauts had taken photos that showed the Earth as a big blue marble, swirling with clouds and continents. But this picture showed the smallness of Earth in the vastness of space.
The late astronomer Carl Sagan eloquently tried to express how he felt about this photo in his book "Pale Blue Dot." This is him reading.
Mr.�CARL SAGAN (Astronomer, Author, "Pale Blue Dot"): Every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species lived there, on a mote of dust suspended in a sunbeam.
Mr.�ROBERT POOLE (Historian, University of Cumbria): Like most people, I saw it in the newspaper not long after it was taken, and kind of intellectually, I thought this is amazing.
GREENFIELDBOYCE: Robert Poole is a historian at the University of Cumbria in the United Kingdom who wrote a book on images of Earth from space called "Earthrise." He says this particular photo shows what an extraterrestrial might see as it approached our solar system.
Mr.�POOLE: This is not our view. We've managed to go out and get the view that somebody else might have, whereas the early Apollo pictures of the blue marble were our own view of Earth.
GREENFIELDBOYCE: Two decades later, pictures like this are still few and far between. They are not exactly easy to take. In fact, we almost didn't get this one. Carl Sagan lobbied for it early in the Voyager 1 mission, but others objected that taking it might fry the spacecraft's camera. Candice Hansen-Koharcheck says that's because the Earth is so close to our extremely bright sun.
Ms.�HANSEN-KOHARCHECK: There was a reluctance to take any kind of risk when we would point back towards the sun. We didn't want to accidentally damage the cameras in any way.
Mr.�EDWARD STONE (Chief Scientist, Voyager Mission): Oh, there was a lot of debate as to what its value would be.
GREENFIELDBOYCE: Edward Stone was and still is the chief scientist for the Voyager mission.
Mr.�STONE: It was not a scientific image. It was really, I think, an image to sort of declare that here, for the first time, we could take such an image, and second of all it provided a new perspective of Earth and its place in our solar neighborhood.
GREENFIELDBOYCE: But the idea was shelved for years, as Voyager 1 flew through the solar system and did its science. In 1989, the mission was winding down, some staff was going to leave, and Carl Sagan made a last-minute request to please, please, take this unique photo before the opportunity disappeared forever. Edward Stone says the decision went to the top levels of NASA.
Mr.�STONE: Because it was going to extend the mission in terms of imaging capability for an additional six months or so, and that of course did cost money.
GREENFIELDBOYCE: Officials decided to go for it. In the time zone used by the Voyager 1 mission, it was Valentine's Day, 1990. The spacecraft turned its cameras towards Earth, and later, the image was released to the world to great fanfare.
But it never really captured the popular imagination like the famous Apollo images.
Mr.�STONE: I think it was hard - it's still hard, to get really your head around the fact that our solar system is so immense compared to Earth.
GREENFIELDBOYCE: Edward Stone says to get the full impact of this photo, you really have to see it up on a wall as part of large panorama that Voyager 1 took of the solar system's distant planets.
Candice Hansen-Koharcheck says her NASA center used to have this mosaic of photos up in an auditorium.
Ms.�HANSEN-KOHARCHECK: And to show the whole thing, it covered, oh, I don't know, 12 or 14 feet.
GREENFIELDBOYCE: Of mostly empty black space. The planets looked like little pinpricks of light. One of them was labeled Earth.
Ms.�HANSEN-KOHARCHECK: One of the guys that took care of that display told me one time that he was forever having to replace that picture because people would come up to look at it, and they would always touch the Earth.
GREENFIELDBOYCE: Voyager 1 is now about three times farther away than it was 20 years ago. The spacecraft still routinely phones home, although its cameras no longer take photos. But if it could send back another picture, the little dot that's Earth would look even fainter and even smaller. Nell Greenfieldboyce, NPR News.