Twenty-four years ago, NASA's Voyager One space probe sent back the mesmerizing image of what Carl Sagan called "a pale blue dot," Earth captured from a distance of 3.7 billion miles. The image seemed to condense all our earthly concerns into one tiny fleck of light, as Sagan put it, "a very small stage in a vast cosmic arena."
Now NASA's Juno spacecraft, currently on its five-year journey to Jupiter, has brought back another perspective: the first-ever video of the moon as it orbits Earth, presented on Tuesday at the meeting of the American Geophysical Union in San Francisco
"This is what Earth would look like to an alien, looking at us with a telescope like Galileo had," said Juno's principal investigator, Scott Bolton.
"In the movie, you ride aboard Juno as it approaches Earth and then soars off into the blackness of space. No previous view of our world has ever captured the heavenly waltz of Earth and moon."
Juno is looking for clues into the formation of the solar system’s largest planet. Launched in 2011, the spacecraft completed a speed-gathering slingshot orbit around the Earth, necessary to propel the spacecraft 400 million miles to Jupiter.
That fly-by gave Juno scientists a rare opportunity to film what Bolton called the "cosmic dance" between the Earth and its moon.
The fly-by also provided a chance to try out some citizen science. During the four hours that Juno dipped closest to the Earth, at least 1400 amateur radio operators from around the world transmitted a greeting in Morse code, hoping the collective signal would be strong enough to be picked up by Juno. It worked.
Those six beeps -- four, then two -- say, in Morse code, "Hi!"
It's the first time a NASA spacecraft has picked up radio signals sent intentionally from citizen scientists on Earth, says NASA's Scott Bolton.
“At first we weren't sure whether it would work,” says Bolton, “but if you had enough ham radio operators working together, there would be enough power, enough energy in their signal for us to see it.”
If all goes according to plan, Juno will fall into orbit around Jupiter on July 4, 2016.