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Planets galore! Saturn probe's big pic finally unveiled

NASA / JPL-Caltech / SSI

Saturn is surrounded by planets and moons in a mosaic assembled from images captured by NASA's Cassini probe on July 19. See the 9,000-pixel-wide version.

Almost four months after NASA's Cassini orbiter turned around and took a picture of Saturn, the big picture is finally out — and it's a stunner.

The backlit picture of the ringed planet includes Earth's tiny speck and the even tinier speck representing our moon. But that's not all: A full-resolution image reveals Mars and Venus, as well as seven of Saturn's moons. The mosaic was assembled from 141 wide-angle images from Cassini, selected from hundreds of pictures that were taken over the course of just four hours on July 19. The fact that the view included our home planet sparked a campaign to get Earthlings to look up at Saturn and smile for the camera.

Carolyn Porco, head of Cassini's imaging team, called it "The Day the Earth Smiled" — and you can easily imagine her smiling as she wrote at length about the finished image for her "Captain's Log" on Tuesday.

"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," Porco said.

The full image takes in nearly 405,000 miles (650,000 kilometers) across Saturn and its inner ring system. In the enhanced photo, the E ring shines like an evanescent halo around the planet, with the tiny moon Enceladus sparkling on its left edge.

"This mosaic provides a remarkable amount of high-quality data on Saturn's diffuse rings, revealing all sorts of intriguing structures we are currently trying to understand," Matt Hedman, a Cassini participating scientist at the University of Idaho, said in a NASA news release. "The E ring in particular shows patterns that likely reflect disturbances from such diverse sources as sunlight and Enceladus' gravity."

NASA / JPL-Caltech / SSI

This annotated image pinpoints the location of the planets, moons and other features of interest in Cassini's "Day the Earth Smiled" image. But to see the sights in detail (including Enceladus, which is not in this cropped version of the picture), you should consult the larger-resolution version from NASA.

The "Pale Blue Dot" picture of Saturn, Earth and more follows up on a similar view that was taken in 2006, relatively early in the $3.3 billion, nine-year-long mission at the ringed planet. It's not often that Cassini can get this sort of big picture from behind Saturn, because mission planners have to make sure to avoid the sun's camera-killing glare. July 19 provided the perfect photo op for a backlit planetary family portrait.

"With a long, intricate dance around the Saturn system, Cassini aims to study the Saturn system from as many angles as possible," said the Cassini mission's project scientist, Linda Spilker of NASA's Jet Propulsion Laboratory. "Beyond showing us the beauty of the ringed planet, data like these also improve our understanding of the history of the faint rings around Saturn and the way disks around planets form — clues to how our own solar system formed around the sun."

Cassini is due to continue studying Saturn and its moons for four more years. The current plan calls for the bus-sized spacecraft to be sent to its destruction in the planet's atmosphere on Sept. 15, 2017, almost 20 years after its 1997 launch. But who knows? With pictures like these, maybe it'll be worth keeping the probe in action even longer.

The Cassini spacecraft is sending back unprecedented imagery of Saturn, its rings and its moons. Click "Launch" to see some of the greatest hits from the Cassini mission.

More about the Day the Earth Smiled:

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.