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Mooning over the night sky's marvels

NASA / JPL-Caltech / SSI

NASA's Cassini orbiter captured this view of Saturn on June 15, from a distance of about 1.8 million miles (2.9 million kilometers). The rings' shadow runs across the planet's sunlit side. The speck in the lower left corner is Enceladus, a 313-mile-wide (504-kilometer-wide) moon of Saturn.

NASA's Cassini sent back this big, beautiful, black-and-white picture of Saturn — but what's that little white speck in the corner?

The image, unveiled by Cassini's imaging team on Monday, shows tiny Enceladus at lower left. It's just 313 miles wide (504 kilometers wide), and yet it shines brightly from a distance of 2 million miles or so. Enceladus is arguably as intriguing as Saturn, and here's why: The icy moon has geysers of water spouting up from cracks in its surface, suggesting that there's a deep ocean and perhaps even some sort of life down below.

To get a more imaginative view of Enceladus, check out this posting on the io9 blog, featuring an illustration from "Planetfall: New Solar System Visions," a big, beautiful, full-color coffee-table book by Michael Benson. NPR's Robert Krulwich showed off the same image earlier this month on his Krulwich Wonders blog.

Enceladus is just one of the moons of the solar system that's been soaking up the spotlight lately: Also this month, NASA's Curiosity rover watched Mars' two moons, Phobos and Deimos, pass over the sun's disk during a series of mini-eclipses. The rover won't see such a sight again for 11 months or so. Here's a smooth animation of Deimos' transit from Nahum Chazarra on UnmannedSpaceflight.com. And if you haven't seen it already, you'll want to catch up with the sight of a crescent Phobos in Mars' dusky sky

Shine on, Harvest Moon
Our own moon is definitely worth watching over the next few days: Saturday brings a "Harvest Moon" — that is, the full moon that's closest to the September equinox. That's traditionally a good moon to bring in the harvest by, since it lights up the whole night for late-working farmers.

The Harvest Moon also can serve as a guidepost for finding the planet Uranus in the night sky, although the moon's glare interferes with the view this weekend. If you'd like some extra help, the Slooh Space Camera is planning a couple of online viewing parties over the weekend — with Uranus as the guest of honor. Video feeds will be coming in to the Slooh website from a variety of observatories, and a panel of experts will provide commentary. The first show begins at 7 p.m. ET on Saturday, with an encore performance at 10.

Next week, the moon continues to act as a guide, as Sky & Telescope's Alan M. MacRobert explains. On Oct. 3, the moon lingers near the Pleiades star cluster. The next night, it sits near the bright red star Aldebaran in the constellation Taurus. And on Oct. 5, the waning moon hangs out with Jupiter, starting around 10 p.m.

This weekend is also a good time to look for the International Space Station as well as the European Space Agency's Automated Transfer Vehicle, which undocked from the station today. To find out when and where to look, check out NASA's satellite sighting database.

Where in the Cosmos
Cassini's picture of Saturn and Enceladus served as today's "Where in the Cosmos" picture puzzle on the Cosmic Log Facebook page. It took just a few minutes for Ian Slota to solve the riddle and report that the speck in the picture was Enceladus. As a reward, I'm sending Ian a pair of big, beautiful, cardboard 3-D glasses, courtesy of Microsoft Research's WorldWide Telescope project. Those glasses will come in handy for seeing 3-D pictures of Saturn's moons. Click the "like" button for the Cosmic Log Facebook page, and you too may be a winner in next week's "Where in the Cosmos" game.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ circles. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter. You can also check out "The Case for Pluto," my book about the dwarf planet and the search for new worlds.