Viewpoint: Saturn snapped as Earth smiled

Saturn viewed from the Cassini spacecraft

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The US space agency (Nasa) has released a spectacular new picture of the Planet Saturn, acquired by the Cassini spacecraft in July. The image was produced as part of The Day The Earth Smiled Project, which was led by Dr Carolyn Porco. She describes how and why the picture was put together.

Four months ago, our cameras on Cassini were commanded to execute a routine imaging sequence during an event that was anything but routine.

On 19 July, an array of overlapping images framing Saturn, its entire ring system and a host of its moons was acquired while Cassini was deep in the shadow created by the planet's eclipse of the Sun.

This arrangement of Sun, Saturn, and machine made for a rare opportunity to image from the outer Solar System the planets in close to the Sun.

The intent: To catch a precious glimpse of our own planet - tiny, remote, alone - as it would be seen from a billion miles away.

Images of this nature had been taken before. The famous Voyager 1990 "Pale Blue Dot" image of Earth became, in the hands of Carl Sagan, a romantic allegory of the human condition and an inspirational call to environmental protection and planetary brotherhood.

And Cassini's previous 2006 version, taken from Saturn orbit, showing the startling juxtaposition of our dot of a planet beside the enormity of Saturn's rings, became the most beloved Cassini image.

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That is our home, with every last one of us on it - you, me, the folks down the block, even those on the opposite side of the Earth. We all inhabit that lovely blue dot”

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But from the very start, the plans for the 19 July mosaic included something very special: If all went well, the images would capture a glimpse of Earth alongside Saturn and its rings at the very moment that people all over the globe would be contemplating their connectedness to each other and to all life on Earth, appreciating the rarity of our planet within the Solar System, marvelling at their own existence, and rejoicing at the very thought of having their picture taken from a billion miles away.

And contemplate, appreciate, marvel and rejoice they did!

From Pennsylvania: "What a great way to feel connected to the Universe, the planet, and every single person on it. We are truly all in this together."

From the UK: "What a privilege to be part of such an event with so many people worldwide."

From somewhere unknown: "At the appropriate time, I turned my face to the sky and spent a few minutes watching and listening to what life on Earth was like, right there. What a feeling of connection and oneness with the miracle that is life on Earth. This experience was beyond meaningful; it was transcendent. What a beautiful thing."

From upstate New York: "I've been entranced by this project ever since I heard about it and was determined to join in the celebration. We may not be unique... we may be transient... we may be only flying along on a dust mote. But for 15 minutes, we were there, we were aware, and we smiled."

After much work, the mosaic that marks that moment the inhabitants of Earth, including the four above, looked up wherever they were and smiled at the sheer joy of being alive, is finally here.

In its combination of beauty and meaning, it is perhaps the most unusual image ever taken in the history of the space programme.

Saturn

Saturn taken by the Cassini probe
  • Saturn is the sixth planet from the Sun and has a prominent icy ring system
  • Although it is the second largest planet in the Solar System, it is the least dense and would float in water
  • It has 62 satellites - the largest, Titan, is the only moon in the Solar System with a substantial atmosphere
  • Launched in 1997, Cassini-Huygens is a joint US-Europe mission to explore Saturn and its moons

Have a look and you will discover a universe of marvels. The brightly rimmed globe of Saturn and its main rings aglow with sunlight streaming through them take centre stage.

On the left, embedded in the enormous, gossamer blue E ring, is the brilliant moon Enceladus, gleaming in the reflected light of Saturn and the sparkle of a hundred towering geysers, and likely the most promising place in all the Solar System to access alien life.

A careful examination uncovers the shadow cast by this moon through the spray of smoke-sized icy particles created by those geysers, like a telephone pole might cast a shadow through a fog.

Below and to the right of Enceladus is Tethys, a moon about a third the size of ours, illuminated by Saturn-shine. On the other side of the planet, to the upper right, is Mimas - only a crescent but also casting a faint shadow through the E ring.

And on it goes - more moons and faint rings for anyone caring to take the time to wander.

Now, look one more time. There, below the main rings and to the right of the globe of Saturn, far in the distance and seemingly lost in the radiance of the scene, lies a small speck of blue light, floating in a sea of stars.

That is our home, with every last one of us on it - you, me, the folks down the block, even those on the opposite side of the Earth. We all inhabit that lovely blue dot.

And more than this - the image of that dot captures the very moment, frozen in time, when the inhabitants of our planet took a break from their normal activities to go outside and acknowledge our "coming of age" as planetary explorers and the audacious interplanetary salute between robot and maker that this image represents.

I hope long into the future, when people look again at this image, they will recall the moment when, as crazy as it might have seemed, they were there, they were aware, and they smiled.

Annotated Saturn The positions of the objects are inside the circles. The squares contain enlarged views
Pale blue dot Earth and the Moon are seen as a blue dot at the bottom right of the image

Dr Porco is the Imaging Team Leader on the Nasa/Esa/Asi Cassini mission. She was also instrumental in helping frame the Earth for its famous Pale Blue Dot portrait by Voyager. You can follow Dr Porco on Twitter and read more about her work and that of her imaging team on the CICLOPS website.

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