Gallery: Give Thanks for Cassini, One of the Greatest Space Missions Ever
01Saturn
A mosaic of 36 Cassini images, captured on Oct. 10, 2013, and assembled into this incredible portrait by Gordan Ugarkovic. Among other details, you can see the hexagon at Saturn's north pole and the remnants of a giant storm that wrapped itself around the planet two years ago. ([*Image: NASA/JPL/Space Science Institute/Gordan Ugarkovic*](http://www.nasa.gov/mission_pages/cassini/multimedia/saturn20131017.html))
02Enceladus
Enceladus, a tiny, icy moon turns out to be one of the more active bodies in the solar system. Thank Cassini for finding out in 2005 that [dozens of geysers erupt from cracks](http://www.sciencemag.org/content/311/5766/1393) in the moon’s south pole. The jets contain [water, salts, nitrogen, and carbon-containing compounds](http://sci.esa.int/cassini-huygens/48829-cassini-samples-the-icy-spray-of-enceladus-water-plumes/) – all the ingredients needed to kick-start life. Scientists are studying how the jets’ activity waxes and wanes as Enceladus orbits Saturn, and are wondering whether there’s an ocean beneath the small moon’s crust – like the one under the [Jovian satellite Europa](https://solarsystem.nasa.gov/europa/home.cfm). (*Image: Enceladus illuminated by Saturnshine. [NASA/JPL-Caltech/Space Science Institute](http://www.ciclops.org/view/7606/By-the-Pale-Saturn-light)*)
03Titan
What lay beneath Titan’s thick, orange, nitrogen shroud was a mystery until Cassini pierced the haze and glimpsed the surface (it also dropped the Huygens lander [onto the moon’s surface](http://nssdc.gsfc.nasa.gov/planetary/titan_images.html) in 2005). Titan is the only other body in the solar system with liquid on its surface: It has [hydrocarbon lakes](http://photojournal.jpl.nasa.gov/jpegMod/PIA09180_modest.jpg) and seas, shores and [rivers](http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20121212/), and [seasonal rainfall](http://www.sciencemag.org/content/331/6023/1414.abstract) like on Earth. This mysterious, potentially life-friendly moon is also home to a [cryovolcanic region](http://astrogeology.usgs.gov/geology/titan-cryovolcanism) that deposits the moon’s slushy innards on its surface. Now, scientists think there could be a liquid water ocean hiding beneath its crust. (*Image: Titan and Dione, with Saturn's rings. [NASA/JPL-Caltech/Space Science Institute](http://www.ciclops.org/view.php?id=6783)*)
04Saturn Moon Zoo
There are five moons in this photo, each dramatically different from the others. Janus, on the far left, is cratered, porous, and icy. Pandora, within the rings, is a ring-herding moon. Gleaming and bright white in the center of the image is Enceladus, a geologically active world. On the right is Rhea, Saturn's second largest satellite, which might have a dust ring of its own. And Mimas, peeking out from behind Rhea, is responsible for creating the Cassini gap in the rings. Cassini is helping scientists understand how such diverse worlds formed from the same ingredients, around the same planet.(*Image: [NASA/JPL-Caltech/SSI](http://www.ciclops.org/view.php?id=6850)*)
05Iapetus
Iapetus, one of Saturn’s largest satellites, has been a puzzle since the astronomer Giovanni Domenico Cassini first spotted it in 1671. Oddly, he could only see the moon when it was on Saturn's western side. Cassini eventually deduced that this was caused by half of it being a bright, blazing white and the other half being coal black. More than 300 years later, the spacecraft named after Cassini [helped discover why](http://www.swri.org/9what/releases/2009/Iapetus.htm): The moon is tidally locked, so it doesn't rotate with respect to Saturn. The hemisphere that's always facing front has been plowing through [dark, dusty particles](http://www.ciclops.org//view_media.php?id=17345&js=1) shed by a different Saturn satellite, the rogue moon Phoebe. Untouched by Phoebe's dust, Iapetus' backside [stays a pristine white](http://adsabs.harvard.edu/abs/2010DPS....42.0105T). (*Image: [NASA/JPL/Space Science Institute](http://www.ciclops.org/view.php?id=3787)*)
06Rings
Rings scientists rejoiced when Cassini arrived at Saturn: Finally, they could get a good look at the icy aggregates that form one of the most spectacular sights in the solar system. Though they measure nearly 200,000 miles across, the rings are incredibly thin: The main rings average [only a few stories tall](http://hubblesite.org/reference_desk/faq/answer.php.id=11&cat=solarsystem). Passing objects can easily perturb them. Since 2004, Cassini observations have revealed a population of moonlets hiding within the rings, mysterious spokes and disruptions, and the ripples produced by cosmic debris impacts. In one case, the team detected reverberations produced when a comet smashed into the rings [600 years ago](https://www.sciencenews.org/article/saturns-rings-tell-comets-tale). (*Image: [NASA/JPL/Space Science Institute](http://www.ciclops.org/view/5404/A-Full-Sweep-of-Saturns-Rings). Be sure to take a look at the [full-size image](http://www.ciclops.org/view_media/26501/A-Full-Sweep-of-Saturns-Rings).*)
07Phoebe
As it arrived in the Saturnian system, Cassini swooped in for a close look at Phoebe, one of Saturn’s weirder moons. It’s irregularly shaped, orbits in the wrong direction, is super dark, and is at least four times farther from Saturn than its nearest neighboring moon. Cassini observations suggest that Phoebe wasn’t born around Saturn, but was [heisted from the Kuiper Belt](http://www.nature.com/nature/journal/v435/n7038/full/nature03384.html). And the dark dust flying off the moon not only colors Saturn’s other satellites, but it creates a massive, nearly invisible ring known (appropriately) as [the Phoebe ring](http://www.nature.com/nature/journal/v461/n7267/pdf/nature08515.pdf). (*Image: [NASA/JPL/Space Science Institute](http://www.ciclops.org/view/197/The-Face-of-Phoebe)*)
08Aurora
This looks like the entrance to hell or a close-up of a lizard's eye, but it's really a composite infrared image showing an aurora (light blue) above Saturn's north pole hexagon. Saturn's auroras are [unlike any](http://www.nasa.gov/mission_pages/cassini/media/cassini-20081112.html) seen in the solar system: Instead of lighting up a ring around the pole, they sometimes form more of a cap. Auroras are produced when charged particles interact with a planet's magnetosphere, but because Saturn's auroras can be so weirdly shaped, scientists think there's also something weird about how the planet's magnetic field interacts with its atmosphere and solar winds. Cassini also gave us [these astonishing videos](http://www.ciclops.org/view.php?id=5970) of Saturn's polar lights in motion. (*Image: [NASA/JPL/University of Arizona](http://www.nasa.gov/mission_pages/cassini/multimedia/pia11396.html)*)
09Propeller Moons
Hiding within Saturn’s rings are thousands (maybe millions) of tiny moonlets, each no more than a kilometer across. Cassini discovered this shortly [after arriving](http://www.ciclops.org/view.php?id=1846) at Saturn: They’re way too tiny to have been spotted by anything other than a spacecraft getting all up in the rings’ business. Telltale propeller marks, like the ones three-quarters of the way down in this image, give away the moonlets’ locations (this particular propeller has been named "Bleriot"). Scientists are studying the motion of the moonlets within the ring plane, and using them as proxies for understanding how planets form and migrate through the protoplanetary dusty disks. (*Image: [NASA/JPL-Caltech/Space Science Institute](http://www.ciclops.org/view.php?id=7459)*)
10Mimas
Tiny Mimas is the smallest spherical body in the solar system. Less than 250 miles across, the moon is scarred by a massive, 80-mile wide crater with a big peak in the middle. Called the Herschel crater, it’s this feature that makes the moon look like the Death Star. But that's not all Mimas resembles. Cassini peered at the moon’s surface in the infrared and discovered a different alter-ego: Pac-Man. Daytime temperature distributions on Mimas' surface form a [shape that looks like our favorite, chompy hero](http://www.ciclops.org/view.php?id=6297). (*Image: Herschel crater, straight ahead. [NASA/JPL/Space Science Institute.](http://www.ciclops.org/view.php?id=728)*)
11SuperStorm
In late 2010, a massive storm began churning in Saturn’s northern hemisphere. Over two months, it wrapped around the planet, eventually crashing into itself like a confused snake eating its own tail. Before it fizzled in August 2011, the storm stretched over roughly 190,000 miles. At times, lightning flashed [more than 10 times each second](http://www.ciclops.org/view.php?id=6818). Cassini [tracked the storm](http://www.ciclops.org/view.php?id=6865) as it grew longer, and longer, and longer, and found out that the tempest was powerful enough to dredge [water ice from the planet's depths](http://www.sciencedirect.com/science/article/pii/S0019103513002431) and deposit it near the top of the atmosphere. (*Image: Super Saturnian storm, captured Feb. 25, 2011. [NASA/JPL-Caltech/SSI](http://www.ciclops.org/view.php?id=6738)*)
12Hexagon
Saturn’s north pole is home to an enigmatic hexagon, first spied by the Voyager spacecraft in the early 1980s. Thanks to Cassini we have this amazing picture of the strange geometric phenomenon. We still don’t know why a six-pointed figure adorns the planet’s top pole. Is it an atmospheric standing wave? A solitary storm? A [gradient in wind speed](http://www.planetary.org/blogs/emily-lakdawalla/2010/2471.html)? But scientists are [hoping to find out](http://stag-komodo.wired.com/wiredscience/2013/11/end-of-cassini-science/). (*Image: [NASA/JPL-Caltech/Space Science Institute](http://www.ciclops.org/view.php?id=7660)*)
13Hyperion
Most moons that aren't spherical look somewhat like cratered potatoes. Not Hyperion. This irregularly shaped moon looks like a honeycomb. It behaves weirdly, too, neither spinning at a constant rate nor maintaining a constant orientation. In other words, it tumbles through its orbit. Cassini observations showed that the [moon is covered in ice](https://www.sciencenews.org/article/frosted-honeycomb-moon) and is incredibly low in density, more like a comet. The observations suggest that Hyperion may have formed far, far away before being snared by Saturn. (*Image: [NASA/JPL/Space Science Institute](http://www.ciclops.org/view.php?id=1507)*)
