Cassini’s Postcard to Earth

The Pale Blue Dot, an image of the Earth from a distance of 3.7 billion miles away, is one of the most iconic pictures in the history of astronomy. Photographed by Voyager 1 in 1990, as the craft offered a final farewell to the Solar System, the image depicted our planet as a blue pinprick in a vast nothingness, a “mote of dust suspended in a sunbeam”, to quote Carl Sagan.

Pale_Blue_Dot

>>above: the Pale Blue Dot. At this resolution, the Earth is almost invisible, located half-way down the ray of sunlight on the right. Click to enlarge. Image by NASA.

Now, I’m not going to compete with Sagan’s original description of the image, which can be found here, but it’s plain to see the effect that the photograph had on a public still coming to terms with their position in the universe.

Voyager 1 made a mockery of the human race – our generations of war and religious bigotry – by depicting the species as invisible in the gloom of deep space. Conversely, as the only planet in the universe known to harbour life, the importance of the Earth could not be overstated. Even at 0.12 pixels in size, it stands out as an oasis in the darkness.

Given the significance of Voyager’s postcard to the Earth, it should come as no surprise that NASA has attempted to recreate the image, some 23 years later, with a new generation of spacecraft. This morning, the Cassini-Huygens and MESSENGER probes, currently in orbit around Saturn and Mercury, respectively, released the following pictures:

PIA17038_fig1

//above: the image from Cassini (left) was taken from 900 million miles away, using the massive body of Saturn as a sun-shield. The MESSENGER probe, which is searching for moons around Mercury, snapped our homeworld from 61 million miles away. Click to enlarge. Image by NASA.

It’s inevitable that images like the above will become ubiquitous as humanity expands into space. However, in 2013, they are still sufficiently rare to be awe-inspiring. To borrow words from Carl Sagan:

“Consider again that dot. 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.”

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