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Earth’s cry, Heaven’s smile (Science Advent 1)

(As I did last year, I’m posting a science-related image with a brief comment every day until December 25. Today is the first entry, so check back every day after for a new post, or watch the Science Advent 2013 tag. Tip o’ the pendulum to Santana for today’s title.)

Day 1

The Day Earth Smiled: a mosaic of images from the Cassini probe when it passed beyond Saturn so that the planet eclipsed the Sun. [Credit: NASA/JPL-Caltech/SSI]

The Day Earth Smiled: a mosaic of images from the Cassini probe when it passed beyond Saturn so that the planet eclipsed the Sun. Earth is a tiny dot in this picture; every single living human being is on that dot. Click to see the full-resolution image, which is much larger. [Credit: NASA/JPL-Caltech/SSI]

Those of us bound to Earth will never see this view in person. It required taking a space probe — the Cassini explorer —  past Saturn so that the planet was between it and the Sun. Saturn itself is shadowed, but its rings are composed of ice and rock, so they reflect enough light to cast an eerie glow over the entire image. Additionally, the rings are very thin compared to their width: in some places, they are no more than 10 meters thick. The ring particles are spread out enough to let light or even a spacecraft pass through.

The highest resolution image linked above contains Saturn's moon Enceladus, which is barely more than a dot...yet you can see the cryovolcanoes that produced Saturn's E ring if you look closely. [Credit: NASA/JPL-Caltech/SSI]

The highest resolution image linked above contains Saturn’s moon Enceladus, which is barely more than a dot…yet you can see the cryovolcanoes that produced Saturn’s E ring if you look closely. [Credit: NASA/JPL-Caltech/SSI]

Saturn’s rings are shaped by a number of forces, including the conflicting tugs from the planet and its moons. These influences create the narrow gaps and ripples you can see in the image. Additionally, the diffuse blue ring farthest from Saturn is the E ring, formed from material ejected by the moon Enceladus from its ice volcanoes — which you can even see in the image! For all the details about what’s in this image, see the Cassini image page, Phil Plait’s summary, and Emily Lakdawalla’s video explanation.

That dot is Earth. You're somewhere in that dot. [Credit: NASA/JPL-Caltech/SSI ]

That dot is Earth. You’re somewhere in that dot. [Credit: NASA/JPL-Caltech/SSI ]

However, there are a few more dots hiding in this image: Venus, Mars, and Earth. Yes, you’re in this picture. For that reason, many of us gathered the day Cassini collected the images to make this mosaic to wave at Saturn for The Day Earth Smiled. But whether or not you participated in one such gathering, you’re here. This is yours, and Cassini — indeed all of science — is yours to share.

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