Last Friday, a remarkable thing happened, which received a lot of publicity, especially for space fans: the Earth had its photo taken – from Saturn! The Cassini spacecraft took the images, which were used for The Day the Earth Smiled event, showing the Earth as a very tiny blue speck in the distance, with Saturn and its rings looming in the foreground. Zooming in closer, the Moon can also be seen. How cool is that? But that’s not all… although it didn’t seem to get as much attention, the Earth and Moon also had their picture taken from Mercury, by the MESSENGER spacecraft, on the same day!
Official versions of the Cassini images haven’t been published yet, but the raw images are now available, and they are beautiful. The image above is an RGB colour composite, by Jason Major, of the original photo. The very tiny dot below the rings is Earth, about 1.5 billion kilometres (900 million miles) away. The second image is a zoomed-in view, showing both the Earth and Moon together.
Similar images had been taken a couple of times before, but this is the first one to show both the Earth and Moon as separate objects, as seen by Cassini near Saturn. This was also the first time that advance notice had been given for this unique photo opportunity, allowing people to “wave at Saturn” while Cassini took its photos.
As Linda Spilker, a Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, eloquently stated, “We can’t see individual continents or people in this portrait of Earth, but this pale blue dot is a succinct summary of who we were on July 19. Cassini’s picture reminds us how tiny our home planet is in the vastness of space, and also testifies to the ingenuity of the citizens of this tiny planet to send a robotic spacecraft so far away from home to study Saturn and take a look-back photo of Earth.”
In the MESSENGER images, both the Earth and Moon can be more easily seen, as Mercury is much closer than Saturn, about 98 million kilometres (61 million miles) away. These images were taken as part of a search for possible tiny as-yet undiscovered moons of Mercury. The images are slightly overexposed and saturated, resulting in the larger than normal appearance of the Earth and Moon and the downward-pointing “tails.”
“That images of our planet have been acquired on a single day from two distant solar system outposts reminds us of this nation’s stunning technical accomplishments in planetary exploration,” said MESSENGER Principal Investigator Sean Solomon. “And because Mercury and Saturn are such different outcomes of planetary formation and evolution, these two images also highlight what is special about Earth. There’s no place like home.”
Paul Scott Anderson is a freelance space writer with a life-long passion for space exploration and astronomy. He currently writes for AmericaSpace, Universe Today and Examiner.com. His own blog The Meridiani Journal is a chronicle of planetary exploration.