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.

Astronomers are abuzz over sightings of a flash on Jupiter — which suggests that the giant planet has taken another bullet for the solar system team.

Monday's report follows Jovian impacts in 2009 and 2010. As in those earlier cases, the call has gone out to look for any visible scars on Jupiter's cloud tops. That would be a sure sign that an asteroid or comet was drawn in by the planet's gravitational pull, potentially saving us from a cosmic collision threat.

"It's kind of a scary proposition to see how often Jupiter gets hit," said George Hall, an amateur astronomer from Dallas who captured the flash on video this morning.

Hall didn't actually see the hit when it happened. Early Monday morning, he brought out his 12-inch Meade Schmidt-Cassegrain telescope with the Point Grey Flea3 video camera attached, just to capture imagery for a composite picture of Jupiter. "Jupiter happens to be ideally positioned at about 6 o'clock in the morning," he explained. "It's right overhead."

That also just happened to be the time when another amateur astronomer from Oregon, Dan Petersen, made a visual observation of the flash. Peterson didn't capture an image of the flare, which lasted only a couple of seconds, but he did send his sighting report to other astronomers.

"I decided to just observe on this particular morning," he said in an email to Philippine amateur astronomer Christopher Go. "Had I been imaging I probably would have missed it while playing with webcam settings and focusing."

Go relayed Peterson's report to the Association of Lunar and Planetary Observers' Jupiter forum, which set the place buzzing. Hall noticed the online hubbub and went back to review the video file on his computer. "I never would have looked" if it weren't for Petersen's report, Hall told me. The time stamp on Hall's video matched up with Petersen's observations — 6:35 a.m. CT,  which is 7:35 a.m. ET or 11:35 GMT.

Hall reported his find, and shared in the accolades from fellow amateurs.

Universe Today's Nancy Atkinson quotes amateur astronomers as saying that the impact area should come back into view starting at about 1 a.m. ET Tuesday. 

Jupiter impacts are of great interest to astronomers, amateur and professional, because they're part of the orbital billiards game that has shaped our solar system. In some cases, the cosmic interloper is destroyed before it has any visible effect on Jupiter's cloud tops. In weightier cases, the object breaks up and leaves black marks on the planet's atmosphere. The case of Comet Shoemaker-Levy 9 in 1994 is the most notable in recent memory.

Beyond the planetary science, there's the "phew" factor: Astronomers suspect that giant Jupiter's gravitational pull serves as a cosmic shield, sweeping up incoming objects that would have a deadlier effect if they were to slam into our planet. Some scientists say that without Jupiter, life on Earth wouldn't have had much of a chance.

How big was the object that caused Monday's flash? Stay tuned: We may get a better fix on that once astronomers get a follow-up look. But Hall probably won't be among the legions keeping watch on Tuesday morning. He's lost enough sleep over the past couple of nights.

"I'm almost 70 years old," he told me, "and it takes a lot out of me to get up at 4:30 or 5."

Update for 1:25 p.m. ET Sept. 11: So far, observers have seen no conclusive sign of a scar left behind on Jupiter by the flash, going by the chatter on the ALPO Jupiter forum and the Cloudy Nights website.

Update for 3:15 p.m. ET Sept. 11: Hall has posted a must-see video of the flash on Flickr. But don't bother popping the popcorn: The video clip is just four seconds long.

More cosmic collisions:

• 2009: Comet may have hit Jupiter
• 2009: See Jupiter's Great Black Spot
• 2010: Something hit Jupiter ... again!
• 2010: What whacked Jupiter? A meteor
• 2010: Yet another news flash from Jupiter
• 2011: Comet impacts scar rings of Jupiter and Saturn

Tip o' the Log to Universe Today.

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+ presence. 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, 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.

Jeff Berkes Photography

Jupiter, the moon and Venus take starring roles in a sunset sky extravaganza, as captured by photographer Jeff Berkes in Pennsylvania's Chester County.

The glitterati of the solar system turned out this past weekend for an Oscar-worthy show: a triple play featuring Jupiter, the moon and Venus in evening skies. This photo, snapped by photographer Jeff Berkes in Pennsylvania's Chester County, is a classic portrayal.

"The crescent moon, Venus and Jupiter have formed a slim triangle in the western skies at sunset," Berkes told me in an email on Sunday. That's not all: Mars rises in the east a few hours after sunset. This sky guide from Space.com's Tariq Malik provides the details. Even if the skies are cloudy all night, you can still get in on the fun online via Slooh.com's planet-watching webcast.

The moon is shifting progressively farther to the east in evening skies, but anytime this week should be prime time for the planetary extravaganza. Got great pictures? Share them via the Cosmic Log Facebook page or msnbc.com's FirstPerson in-box. You'll also want to get a look at the beauties on Jeff Berkes' website as well as at SpaceWeather.com and Space.com.

Update for 7:30 p.m. ET Feb. 27: NBC News' Brian Williams featured a beautiful time-lapse view of Venus, Jupiter and the moon that was captured on Friday night by Roberto Porto on the road to Teide National Park in Tenerife in the Canary Islands. Check it out:

More from Jeff Berkes on PhotoBlog:

• Catch a falling star ... and fall colors
• Meteor quest turns up treasures

Courtesy of Mike Wong, Franck Marchis, Christopher Go & W.M. Keck Observatory

Jupiter seen in three bands of infrared (left), with an overly of 5-micron thermal infrared (center) and on the same night in visible light (small inset at right).

Scientists are getting a detailed look inside the turmoil behind the disappearance — and slow re-emergence — of a prominent stripe of clouds on Jupiter, thanks to some crafty astronomy and help from the planet's icy moon Europa.

Astronomers noticed that the stripe, known as the South Equatorial Belt, disappeared from view last May. Jupiter's famous Great Red Spot is typically found along the edges of this belt. The belt's disappearance was attributed to a deck of white clouds made of ammonia ice that formed when the dry, downwelling winds that normally keep the region clear of high clouds died down. In November, scientists noticed that the belt was re-emerging due to a shift in the cloud cover.

To gain a better understanding of the dynamics behind the disappearance and re-emergence of the belt, scientists created the image above, which shows how the gas giant looks in thermal infrared light, at a wavelength of nearly 5 microns. The thermal IR imagery is shown in bright red and yellow, overlaid on a composite of three shorter near-infrared bands.

The thermal readings reveal how heat from Jupiter's interior is being radiated into space. The three other IR bands, in contrast, capture reflected sunlight. Put them all together and compare them to visible-light images, and scientists get a picture of the thinning, breaking layer of high, bright icy clouds that obscured the belt.

"We see wispy cloud-free regions at 5 microns in the SEB [South Equatorial Belt], but they are much less extensive than the near-infrared dark regions surrounding them," Mike Wong, an astronomer at the University of California at Berkeley, said in an image advisory. "The data show that the change from zonelike to beltlike appearance is a complex process that takes place at different speeds in each layer of Jupiter’s atmosphere."

To make the image, astronomers used the adaptive optics system on the Keck II telescope in Hawaii in a particularly clever way. The system effectively cancels out much of the interference of Earth's atmosphere.

Normally, astronomers flash a powerful laser to create an artificial guide star, which they use to compensate for atmospheric distortions at a rate of 2,000 times per second. Jupiter, however, is so bright that its glare overwhelms the laser guide star. So astronomers went looking for something bright and close to Jupiter. On Nov. 30, Europa was positioned just right to serve that purpose, the image advisory explains.

More stories about Jupiter:

• Jupiter lost a cloud stripe, new photos reveal
• Jupiter's missing cloud stripe bounces back big time
• Scientists to probe for life on Jupiter's moons?
• Jupiter took a double wallop as amateurs watched
• Another news flash from Jupiter

ESA / NASA / Michael Carrol

The joint NASA-ESA Europa Jupiter System Mission would send to orbiters to explore the Jovian moons Europa and Ganymede. It is one of three missions vying to be the next big mission put on by the European Space Agency.

Scientists may finally get a chance to probe Jupiter's moons Europa and Ganymede for signs of microbial life, by looking in what are thought to be liquid oceans beneath their frozen crusts.

The Europa Jupiter Systems Mission is one of three finalists vying to carry out the European Space Agency's next big mission. All three presented mission plans Feb. 3 at a conference in Paris. A final decision is expected this June.

The other two missions vying for funding are the International X-ray Observatory, which could reveal what happens in the vicinity of black holes, and Laser Interferometer Space Antenna, which will "listen" to gravitational waves, giving space-time a sort of soundtrack.

Jupiter moons
All three missions are international collaborations, so Europe's decision is tied to and will have consequences for the priorities of NASA, a partner on all three, and the Japan Aerospace Exploration Agency, a partner on IXO.

Under the joint NASA-ESA Europa Jupiter Systems Mission, NASA will target Europa, an ice-covered moon thought to harbor a liquid ocean beneath its crust; ESA will head to Ganymede, the largest moon in the solar system.

Since the two orbiters are built by different agencies, one could fly without the other, though "you get better results in tandem," noted Michele Dougherty of University College London, who made the case for the joint mission at the Paris meeting, according to Space News.

Having two spacecraft, for example, would give scientists an opportunity to study Jupiter's atmosphere and magnetosphere in three dimensions.

International collaboration
IXO and LISA are considered too big and complicated to fly without international collaboration. Currently, IXO's lack of technical readiness has prompted the U.S. National Academy of Sciences to rank it a lower than LISA for U.S. space-science priorities.

Boosters of both missions say technical hurdles can be cleared and will be well worth the effort. IXO promises to provide the sharpest and most sensitive X-ray views of the Universe, according to team member Kirpal Nandra.

Bernard Schutz, a director at the Albert Einstein Institute in Golm, Germany, likened LISA's ability to "hear" gravitational waves, which are ripples of space-time, would be like adding sound to a silent film of a walk through a jungle. "There are bound to be many things we didn't even expect," he told Nature News.

Which mission is set as a priority in Europe will become clearer this June. NASA has thrown preliminary support behind all three, though guidelines to be laid out March 7 in the final version of the National Academy of Sciences ranking will set the space agency's agenda.

Keep in mind, all the missions are still way out on the horizon: The one ultimately selected wouldn't launch until around 2020.

For more about these missions, check out these stories:

• Bigger, better telescopes to follow Hubble
• NASA, Europe explore mission to outer planets
• Jupiter's moon ocean is rich in oxygen
• Orbiting stars circle each other in minutes

John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).