Carl Sagan and the Pale Blue Dot, Valentine's Day 1990

In 1990, once NASA's twin Voyager probes had completed their grand tour of the solar system, it came time to shut off their cameras to preserve power and memory for the other scientific instruments onboard. But before that happened, there was one last photo opportunity not to be missed. Carl Sagan, a member of the Voyager Imaging Team, persuaded NASA engineers to turn Voyager I's cameras back toward the sun and take the first ever "portrait" of our solar system from outside of it. Taken on Valentine's Day, February 14, 1990, thirty-nine wide-angle views and twenty-one narrow-angle images were combined into the single mosaic image below, a "Solar System Family Portrait," albeit without Mars, Mercury, or Pluto. Centered in a scattered light ray caused by sunlight in the camera's optics is a tiny speck, just .12 pixels in size, seen in the image above. That's Earth from 4 billion miles away — the "pale blue dot" as Sagan called it.

"There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world," Sagan wrote. "To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known."

Below, Sagan's inspiring Pale Blue Dot speech: