MIMAS (SATURN MOON)

And we come to the end of our punt through the waters of the Saturn system, with an examination of its smaller moons CORRECTIONS: 13:49 : Water reacts with the crust, causing the crust to combine with the oxygen in the water and hydrogen to be released. 18:20 : Lagrange points are similar to hills; some are low, rolling and stable, others are narrow and sharp, and require constant readjustment to retain position. 22:32 : As can be plainly seen in the diagram, Iapetus's inclination is over 15 degrees, not 7. To be honest I can't remember where I came up with that one. Universe of Water playlist: https://www.youtube.com/watch?v=M186s319ob8&list=PLa0TgREKn12jUoCK0N4qQVgTgGalS6KDG Me on Facebook: https://www.facebook.com/parallaxicality/?ref=bookmarks Me on Twitter: https://twitter.com/nickrwebb?lang=en-gb

Saturn's moon, Mimas, has an "uncanny resemblance to Darth Vader's favorite spaceship," the Death Star, but have no fear -- it won't try to destroy Saturn. In October the Cassini spaceship got a good look at the moon, and NASA shared the image on Monday. It's so similar to the Death Star, it even has a large round crater that matches the "concave dish" on the Star Wars vessel. Mimas' crater is called the Herrschel Crater, named after the 18th century astronomer who first discovered the moon. https://www.cnet.com/news/nasa-saturn-moon-mimas-death-star-wars-cassini/#ftag=CAD590a51e http://www.wochit.com This video was produced by YT Wochit News using http://wochit.com

What incredible things will the Cassini spacecraft at Saturn see and do over the next few years? Here's a preview.

Zoom in the Cassini Division region

Mimas (grey dot) digs the Cassini Division. Ring particles are 1m..

One day it will be an amazing scientific accomplishment when we colonize and bring life to a moon like Saturn's icy Enceladus. Subscribe for new videos weekly! 5. Triton Photographs and data sent back from the Voyager 2 spacecraft back in August of 1989 showed that the surface of Triton, Neptune’s largest moon, was made up of nitrogen ice and rock. The suspicion of liquid water being hidden beneath the surface was raised. Even though the moon has an atmosphere, it would be pretty much the same as if it didn’t have one because of how thin it is. The average temperature on the moon is an unbelievable -391 degrees Fahrenheit, making it the coldest body in the entirety of our solar system. 4. Mimas Also known as the “Death Star” moon and for good reason. Mimas is one of Saturn’s icy and rocky moons. Mimas might have an ocean located beneath its cold and unwelcoming -looking surface, which may possibly be better adapted for life. Close study of the Cassini footage by scientists shows that Mimas looks to rock back and forth as it went around on its orbit. This could imply activity underneath its surface. However, scientists were very wary with what they found, stating that there hadn’t been any other signs that point to geological activity. They merely stated that if an ocean was discovered, the moon could definitely be a candidate for being colonized. It’s believed that the theoretical ocean would be about 15 to 18 miles below the surface. If the rocking movement that supports this theory of an ocean proves to be false, then the movement is mostly likely because of a misshapen core due to the strong gravitational pull caused by Saturn’s rings 3. Callisto Exactly the same size as the planet Mercury, Callisto is Jupiter’s second largest moon that looks like it has a large liquid ocean hidden within its icy surface. The surface of Callisto mainly made up of craters and what are basically fields of ice. Callisto also has a relatively thin atmosphere consisting of carbon dioxide. Research that already been performed has suggested that this atmosphere is being filled up again and again by carbon dioxide that is released from below the surface because it is too thin to stay in place. Collected data implies the chance that oxygen could also be actively present inside of the atmosphere, but there would need to be further tests to confirm if this theory holds true. Callisto is positioned in a safe enough space from Jupiter that the giant planet’s radiation levels would be very mild. 2. Ganymede Ganymede happens to be Jupiter’s largest moon and like other masses, in our solar system, it could potentially prove to have water trapped underneath its surface. If you were to compare it to other ice-covered moons, Ganymede’s surface is believed to be relatively thin and should be much easier to break through. This moon also happens to be the only moon with its own gravitational field that creates its own auroras, like the ones that are produced here on earth. Their pattern in movement also leads scientists to theorize there is an ocean trapped underneath the surface. Because of Ganymede’s thin oxygen atmosphere, it is too thin to support our life but maybe enough to support terraforming. Back in 2012, the European Space Agency got the okay to go ahead and launch a mission to go and explore Ganymede and two other of Jupiter’s moons, Europa and Callisto. The operation is scheduled to launch in 2022 and reach the moon 10 years later. Out of the three moons to be explored, scientists believe that Ganymede will have the best environment to study and potentially support life, if possible. 1. The Moon The first moon that mankind would colonate would, of course, be the earth’s very own moon. It’s been described as a good “dress rehearsal” for potential colonization missions in the future because of how close it is to earth compared to all the other moons. Earlier in March of this year, there was a story that was going around that this type of operation could be carried out within the next 10 years or so. NASA astrobiologist Chris McKay is one of the individuals whose onboard with making this mission come to fruition. His opinion is that other missions to the moon have failed because of the high cost, but his team has a plan that requires little compared to previous missions. Although NASA’s current focus is to get humans to land on Mars, McKay says that that won’t come to light until they can first get to the moon and set up permanent bases there first.

For our Final project in Solar Systems Astronomy class

Saturn's Moons and Rings May Be Younger Than the Dinosaurs Some of Saturn's icy moons may have been formed after many dinosaurs roamed the Earth. New computer modeling of the Saturnian system suggests the rings and moons may be no more than 100 million years old. Saturn hosts 62 known moons. All of them are influenced not only by the gravity of the planet, but also by each other's gravities. A new computer model suggests that the Saturnian moons Tethys, Dione and Rhea haven't seen the kinds of changes in their orbital tilts that are typical for moons that have lived in the system and interacted with other moons over long periods of time. In other words, these appear to be very young moons. "Moons are always changing their orbits. That's inevitable," Matija Cuk, principal investigator at the SETI Institute and one of the authors of the new research, said in a statement. "But that fact allows us to use computer simulations to tease out the history of Saturn's inner moons. Doing so, we find that they were most likely born during the most recent 2 percent of the planet's history." The age of Saturn's rings has come under considerable debate since their discovery in the 1600s. In 2012, however, French astronomers suggested that some of the inner moons and the planet's well-known rings may have recent origins. The researchers showed that tidal effects — which refer to "the gravitational interaction of the inner moons with fluids deep in Saturn’s interior," according to the statement — should cause the moons to move to larger orbits in a very short time. "Saturn has dozens of moons that are slowly increasing their orbital size due to tidal effects. In addition, pairs of moons may occasionally move into orbital resonances. This occurs when one moon's orbital period becomes a simple fraction of another. For example, one moon could orbit twice as fast as another moon, or three times as fast. Once an orbital resonance takes place, the moons can affect each other's gravity, even if they are very small. This will eventually elongate their orbits and tilt them from their original orbital plane. By looking at computer models that predict how extended a moon's orbit should become over time, and comparing that with the actual position of the moon today, the researchers found that the orbits of Tethys, Dione and Rhea are "less dramatically altered than previously thought," the statement said. The moons don't appear to have moved very far from where they were born. To get a more specific value for the ages of these moons, Cuk used ice geysers on Saturn's moon Enceladus. The researchers assumed that the energy powering those geysers comes from tidal interactions with Saturn and that the level of geothermal activity on Enceladus has been constant, and from there, inferred the strength of the tidal forces from Saturn. Using the computer simulations, the researchers concluded that Enceladus would have moved from its original orbital position to its current one in just 100 million years — meaning it likely formed during the Cretaceous period. The larger implication is that the inner moons of Saturn and its gorgeous rings are all relatively young. (The more distant moons Titan and Iapetus would not have been formed at the same time.) "So the question arises — what caused the recent birth of the inner moons?" Cuk said in the statement. "Our best guess is that Saturn had a similar collection of moons before, but their orbits were disturbed by a special kind of orbital resonance involving Saturn's motion around the sun. Eventually, the orbits of neighboring moons crossed, and these objects collided. From this rubble, the present set of moons and rings formed." The research is being published in the Astrophysical Journal.

NASA has released a stunning image taken by the Cassini spacecraft which shows three of Saturn’s moons--Tethys, Enceladus, and Mimas. NASA recently released a stunning image taken by its Cassini spacecraft.  It shows three of Saturn’s 62 confirmed moons in one group shot.  Above the planet’s visible rings is Tethys which is 660 miles across, and the two below are Enceladus at 313 miles across and Mimas at 246 miles across. The image was captured on December 3rd from a narrow-angle camera aboard Cassini when it was about 837,000 miles from the Enceladus, the closest moon.  The perspective, according to a press release, is “toward the sunlit side of the rings from about 0.4 degrees above the ring plane.”

The Cassini mission’s much anticipated and final near flyby of Saturn’s moon Enceladus has come and gone. The Cassini Mission’s much anticipated and final near flyby of Saturn’s moon Enceladus has come and gone.  That close encounter occurred on Saturday, December 19th, and the data and images gathered are in the process of being downloaded. Scientists involved with the project expressed mixed emotions. Earl Maize, Cassini project manager at JPL, said, “While we're sad to have the close flybys behind us, we've placed the capstone on an incredible decade of investigating one of the most intriguing bodies in the solar system."  Linda Spilker, the mission's project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, commented, “We bid a poignant goodbye to our close views of this amazing icy world…so much more remains to be done to answer that pivotal question, 'Does this tiny ocean world harbor life?'"  While the near passes are complete, the mission continues through September of 2017.

Although Mimas and Pandora, shown here, both orbit Saturn, they are very different moons. Pandora, "small" by moon standards (50 miles or 81 kilometers across) is elongated and irregular in shape. Mimas (246 miles or 396 kilometers across), a "medium-sized" moon, formed into a sphere due to self-gravity imposed by its higher mass. The shapes of moons can teach us much about their history. For example, one explanation for Pandora's elongated shape and low density is that it may have formed by gathering ring particles onto a dense core. This view looks toward the unilluminated side of the rings from 0.26 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 26, 2015. The view was obtained at a distance of approximately 485,000 miles (781,000 kilometers) from Pandora. Image scale is 3 miles (5 kilometers) per pixel. Mimas is 904,000 miles (1.4 million kilometers) from the spacecraft in this image. The scale on Mimas is 5.4 miles (8.4 kilometers) per pixel. The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov or http://www.nasa.gov/cassini . The Cassini imaging team homepage is at http://ciclops.org . Credit: NASA/JPL-Caltech/Space Science Institute Last Updated: Oct. 13, 2015 Editor: Tony Greicius

Saturn is the crown jewel of the solar system, beautiful and fascinating. It is a gas giant, and has a broad set of rings made of ice particles. Moons create gaps in the rings via their gravity. Saturn has dozens of moons, including Titan, which is as big as Mercury and has a thick atmosphere and lakes of methane; and Enceladus which has an undersurface ocean and eruptions of water geysers. While we are still uncertain, it is entirely possible that either or both moons may support life. This episode was brought to you by Squarespace http://www.squarespace.com -- Table of Contents Saturn is a Gas Giant 0:33 Moons Create Gaps in the Ice Rings 5:17 Dozens of Moons 6:18 Titan’s Methane Lakes 7:56 Enceladus’s Water Geysers 8:33 Life Potential 9:30 -- PBS Digital Studios: http://youtube.com/pbsdigitalstudios Follow Phil on Twitter: https://twitter.com/badastronomer Want to find Crash Course elsewhere on the internet? Facebook - http://www.facebook.com/YouTubeCrashCourse Twitter - http://www.twitter.com/TheCrashCourse Tumblr - http://thecrashcourse.tumblr.com Support CrashCourse on Patreon: http://www.patreon.com/crashcourse -- PHOTOS/VIDEOS Saturn http://saturn.jpl.nasa.gov/multimedia/images/saturn/images/IMG004899.jpg [credit: NASA/JPL-Caltech/Space Science Institute/G. Ugarkovic] Interiors http://solarsystem.nasa.gov/multimedia/gallery/gas_interiors.jpg [credit: Lunar and Planetary Institute] Saturn Ring Plane Crossing http://www.spacetelescope.org/static/archives/images/large/opo9616a.jpg [credit: Erich Karkoschka (University of Arizona Lunar & Planetary Lab) and NASA/ESA] Translucent Rings http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA18295 [credit: NASA/JPL-Caltech/Space Science Institute] Catching its Tail http://www.ciclops.org/view_media/34501/Catching_Its_Tail?js=1 [credit: NASA/JPL-Caltech/Space Science Institute] Enter the Vortex http://www.ciclops.org/view_media/38030/Enter_the_Vortex_In_Psychedelic_Color [credit: NASA/JPL/Space Science Institute] The Rose http://www.nasa.gov/mission_pages/cassini/multimedia/pia14944.html#.VSwz-5TF_Z0 [credit: NASA/JPL/Space Science Institute] Ice http://www.nasa.gov/images/content/205796main_PIA10081-hires.jpg [credit: NASA/JPL/University of Colorado] Saturn’s rings to scale http://www.slate.com/blogs/bad_astronomy/2014/05/02/saturn_s_rings_to_scale_thinner_than_paper.html [credit: NASA/JPL/Space Science Institute] Saturn’s Ring Plane http://en.wikipedia.org/wiki/Rings_of_Saturn#/media/File:Saturn%27s_ring_plane.jpg [credit: NASA/JPL/Space Science Institute - Cassini-Huygens/NASA] Saturn http://saturn.jpl.nasa.gov/multimedia/images/saturn/images/IMG004899.jpg [credit: NASA/JPL-Caltech/Space Science Institute/G. Ugarkovic] Shaping the Drapes (video) http://ciclops.org/view.php?id=1361&js=1 [credit: NASA/JPL/Space Science Institute] Peaks http://en.wikipedia.org/wiki/Rings_of_Saturn#/media/File:PIA11668_B_ring_peaks_2x_crop.jpg [credit: NASA / Jet Propulsion Lab / Space Science Institute] Mimas Cassini http://en.wikipedia.org/wiki/Mimas_(moon)#/media/File:Mimas_Cassini.jpg [credit: NASA / JPL-Caltech / Space Science Institute] Cassini NAC RGB https://www.flickr.com/photos/ugordan/6896462870/sizes/o/in/photostream/ [credit: NASA/JPL-Caltech/Space Science Institute/G. Ugarkovic] Titan http://en.wikipedia.org/wiki/Titan_(moon)#/media/File:Titan2005.jpg [credit: NASA/JPL/Space Science Institute] Titan’s Nile River http://www.esa.int/spaceinimages/Images/2012/11/Titan_s_Nile_River [credit: NASA/JPL–Caltech/ASI] Lakes http://photojournal.jpl.nasa.gov/figures/PIA17655_fig1.jpg [credit: NASA/JPL-Caltech/ASI/USGS] Enceladus http://www.ciclops.org/view_media/39541/Bursting-at-the-Seams [credit: NASA/JPL/Space Science Institute] Iapetus Ridge http://en.wikipedia.org/wiki/Equatorial_ridge#/media/File:Iapetus_706_1419_1.jpg [credit: NASA (Cassini probe), Matt McIrvin (image mosaic)] Hyperion http://ciclops.org/media/ir/2005/1507_3730_1.jpg [credit: NASA/JPL/Space Science Institute] Saturn eclipse mosaic http://en.wikipedia.org/wiki/Rings_of_Saturn#/media/File:PIA17172_Saturn_eclipse_mosaic_bright_crop.jpg [credit: NASA / JPL-Caltech / Space Science Institute]

SciShow Space News takes you to the solar system’s own Death Star -- Saturn’s moon Mimas, where something mysterious is going on. Plus, we share a stunning new photo from the Hubble Space Telescope that holds a few surprises! Hosted by: Caitlin Hofmeister ---------- Like SciShow? Want to help support us, and also get things to put on your walls, cover your torso and hold your liquids? Check out our awesome products over at DFTBA Records: http://dftba.com/artist/52/SciShow Or help support us by subscribing to our page on Subbable: https://subbable.com/scishow ---------- Looking for SciShow elsewhere on the internet? Facebook: http://www.facebook.com/scishow Twitter: http://www.twitter.com/scishow Tumblr: http://scishow.tumblr.com Thanks Tank Tumblr: http://thankstank.tumblr.com Sources: http://news.sciencemag.org/space/2014/10/does-mimas-have-ocean-under-icy-cap http://www.eurekalert.org/jrnls/sci/emb_scipak/pdf/tajeddine141017.pdf https://cornell.app.box.com/mimas http://hubblesite.org/newscenter/archive/releases/2014/39/full/

The Fortean Slip Science Minute 54 Saturn's "Death Star" moon Mimas may contain life. Source: http://www.techtimes.com/articles/18155/20141017/saturn-s-moon-is-harboring-secrets-a-buried-ocean-or-elongated-core.htm Like us on Facebook at... https://www.facebook.com/theforteanslip The Fortean Slip Facebook Group Page https://www.facebook.com/groups/574332809255914/ The Bob Dominguez Site www.night-watchers.com Sasquatch Scoop http://www.sasquatchscoop.com bigfootcrossroads http://bigfootcrossroads.blogspot.com/ "The Machine Thinks" Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 3.0 http://creativecommons.org/licenses/by/3.0/

The smallest of Saturn's main moons, Mimas, wobbles as it orbits. Research reveals it might be due to a global ocean underneath its icy surface. Follow Katherine Biek: http://www.twitter.com/katherinebiek See more at http://www.newsy.com Sources: NASA https://www.youtube.com/watch?v=8CHHPHZIIMs Science Magazine http://www.sciencemag.org/content/346/6207/322 NASA https://www.youtube.com/watch?v=QhTAyeNbU6M BBC http://www.bbc.com/news/science-environment-29613671 The Register http://www.theregister.co.uk/2014/10/17/cassini_spots_death_star_moon_of_saturn_is_unexpectedly_wobbly/ Euronews http://www.euronews.com/2014/10/17/saturn-moon-may-have-life-friendly-underground-ocean/ International Business Times http://www.ibtimes.com/saturns-icy-moon-mimas-may-contain-ocean-could-provide-life-friendly-environments-1706754 Discovery http://news.discovery.com/space/saturns-death-star-moon-may-hide-subsurface-ocean-141016.htm NASA http://www.nasa.gov/mission_pages/cassini/multimedia/pia12867.html Image via: NASA https://www.youtube.com/watch?v=QhTAyeNbU6M

Subscribe here: http://bit.ly/ODNsubs Saturn's icy moon Mimas may have a thin global ocean buried miles beneath its icy surface. Report by Claire Lomas. Current affairs, amazing footage and incredible stories. Welcome to ODN - On Demand News. Formerly the ITN YouTube channel, ODN is your home for the top visual stories happening across the globe. Like us on Facebook: http://bit.ly/ODNface Follow us on Twitter: http://bit.ly/ODNTweets Add us on Google+: http://bit.ly/ODNplus More stories from ODN: Guess who's back? Kim Jon-un: http://bit.ly/KimJong-unReturns Man starts train dance party: http://bit.ly/TrainParty Phone battery explodes in woman's hands: http://bit.ly/PhoneExplodes Has Kim Jong-un lost control of North Korea? http://bit.ly/KimJong-un So a horse walks into a police station: http://bit.ly/PoliceHorse 5 things you should know about Ebola: http://bit.ly/EbolaVirusFacts Rare sighting of sperm whales: http://bit.ly/SpermWhale Peekaboo twins video goes viral: http://bit.ly/1t2WeHB Masked men tie up women and rob shop: http://bit.ly/IlkestonRobbery Watch as astronauts perform spacewalk at ISS: http://bit.ly/ISSWalk Alan Henning's family speak out about beheading: http://bit.ly/ColinLivesey Pride of Britain Awards 2014 red carpet: http://bit.ly/1yJEL9r Deadly Typhoon Phanfone hits Japan: http://bit.ly/Phanfone Man loses arm in shark attack: http://bit.ly/AustraliaShark Why are walruses beaching themselves in Alaska? http://bit.ly/WalrusAlaska See 2013's Most Watched Videos: http://bit.ly/ODN2013 Watch our videos with more a million views: http://bit.ly/ODNMillion

Saturn's wide, but very thin, rings are tilted with respect to its plane of orbit around the Sun. Once every 15 years, the rings are edge-on (perpendicular) to the Sun. During those times, some of Saturn's moons can cast shadows across the rings. This time-lapse movie shows the icy moons Enceladus, Mimas, Dione, and Tethys orbiting Saturn. Enceladus, seemingly chased by Mimas, is first to speed past the rings and in front of the planet. Both moons cast small shadows on the planet, but only Enceladus casts a shadow on the rings. The orbit of Mimas is inclined so that its shadow misses the rings. Dione is next, and its long shadow also tracks across the ring system. As the three moons move across Saturn's disk, the viewer catches a fleeting view of Tethys as it moves behind the planet on the right. The 30-second movie is created from Hubble images taken over a 9½-hour span. The images were taken Nov. 17, 1995, with Hubble's Wide Field and Planetary Camera 2. The movie has a standard aspect ratio, but is presented within a widescreen frame - the black bars along the sides are normal. For more information or to download this video, visit: http://hubblesite.org/videos/video_details/8-moon-shadows-on-saturn For more videos, visit: http://hubblesite.org/videos/

The clip is from "Star Wars: Episode IV - A New Hope".

Pity poor Mimas! The "that's no moon" moon of Saturn ought to be as famous as its sibling Enceladus. All other things being equal, Mimas should be more strongly tidally heated, but this is clearly not the case. This talk will review the latest Cassini findings for both moons, including the astonishing heat flow coming from Enceladus' south pole. It turns out that Mimas' lack of geologic activity is no surprise — the real question is how does Enceladus support its heat flow, active tectonics, and erupting plumes? Episodicity may be key, but even more radical notions have been proposed. These ideas, and perhaps new ones from the 23-24 May Enceladus Workshop at the SETI Institute, will also be discussed.

NASA's Cassini mission caught Mimas flying against the rings. I sequenced these frames after I saved from them from the raw uncalibrated images when they were coming in. Jason H.

Launched three years before the new century... a spacecraft wound its way through the empty reaches of the solar system. On Earth, its progress was little noted, as it swung twice by the planet Venus, then our moon. And Earth. The asteroid belt. And Jupiter. Almost seven years later, on the first of July 2004, the Cassini probe entered the orbit of Saturn. It then began to compile what has become one of the greatest photographic collections of all time, of a giant gas planet, surrounded by colorful rings, guarded by a diverse collection of moons, and millions of tiny moonlets. Within this record, is a trail of clues... pointing to the energy sources and complex chemistry needed to spawn life. What are these mysterious worlds telling us about the universe, and Earth? In the outer reaches of the solar system, a billion and a half kilometers from the Sun... there is a little world known as Enceladus. Nearly all of the sunlight that strikes its icy surface is reflected back into space, making it one of the brightest objects in the solar system. At its equator, the average temperature is minus 198 degrees Celsius. It can rise about 70 degrees higher in grooves that stretch across the south pole like tiger stripes. Looming over it is the giant planet Saturn. In myth, Saturn - the Roman name for the primal Greek God Chronos - was the youngest son of Gaia, or Earth, and Uranus, sky. Wielding a scythe provided by his mother, the story goes, Saturn confronted his abusive father, castrating him. The blood of Uranus flowed into the seas, fertilizing the Earth and giving rise to Enceladus and other giant offspring. Saturn's moon Enceladus has its own tangled story. In 2005, the Cassini spacecraft spotted plumes of water vapor shooting out into space from its south pole. More recent close encounters have revealed jets of water, flavored by slightly salty chemical compounds, spewing out from vents in the rough, cracked polar terrain. That may mean that Enceladus harbors a remarkable secret below its frigid surface: A liquid ocean, and perhaps, a chemical environment that could spawn simple life forms. It's not the only promising stop in the realm of Saturn. The moon Titan is often said to resemble Earth in its early days. It is lined with volcanoes and a hazy atmosphere rich in organic compounds. While Enceladus is the size of Great Britain, Titan is ten times larger, 50% larger than our moon, and the second largest moon in our solar system. We've known about Titan since the astronomer Christian Huygens discovered it in 1655, and Enceladus since William Herschel spotted it in August 1789, just after the start of the French Revolution. Scientists began to investigate these moons in earnest with the launch of the two Voyager spacecraft in 1977. The lineup of outer planets in the solar system allowed the spacecraft to fly past each of them. They disclosed new details about their magnetic fields, atmospheres, ring systems, and inner cores. But what really turned heads were the varied shapes and surfaces of their moons. They've all been pummeled over the millennia by wayward asteroids and comets. A few appear to be sculpted by forces below their surfaces. Neptune's largest moon Triton has few craters. It's marked with circular depressions bounded by rugged ridges. There are also grooves and folds that stretch for dozens of miles, a sign of fracturing and deforming. Triton has geysers too, shooting some five miles above the surface. But on this frigid moon -- so far from the Sun -- the liquid that spouts is not water but nitrogen. Tiny Miranda, one of 27 known moons that orbit Uranus, wears a jumbled skin that's been shaped and reshaped by forces within. Jupiter's moon Io -- orbiting perilously close to the giant planet is literally turning itself inside out. Rivers of lava roll down from open craters that erupt like fountains. Flying by Europa, Voyager documented a complex network of criss-crossing grooves and ridges. In the 1990s, the Galileo spacecraft went back to get a closer look. It found that Europa's surface is a crazy quilt of fractured plates, cliff faces and gullies... amid long grooves like a network of superhighways. How did it get like this? Then, heat rising up through a subsurface ocean of liquid water cracks, and shifts, and spreads the icy surface in a thousand different ways. Europa's neighbors, Callisto and Ganymede, show similar features, suggesting they too may have liquid oceans below their surfaces. Crossing outward to Saturn, Voyager found a similar surface on the moon Enceladus. So when the Cassini spacecraft arrived in 2004, it came looking for answers to a range of burning questions: if this moon and others have subsurface oceans? Do they also have the ability to cook up and support life? And what could they tell us about the origin of life throughout the galaxy?

Mimas is probably the coolest moon in our solar system. Here is why.

Mimas was discovered by the astronomer William Herschel on September 17, 1789. He recorded his discovery as follows: "The great light of my forty-foot telescope was so useful that on the 17th of September, 1789, I remarked the seventh satellite, then situated at its greatest western elongation."[ Mimas is named after one of the Titans in Greek mythology, Mimas. The names of all seven then-known satellites of Saturn, including Mimas, were suggested by William Herschel's son John in his 1847 publication Results of Astronomical Observations made at the Cape of Good Hope. He named them after Titans specifically because Saturn (the Roman equivalent of Kronos in Greek mythology), was the leader of the Titans. Discovered by William Herschel Discovery date September 17, 1789 Orbital characteristics Mean orbit radius 185 520 km Eccentricity 0.020 2 Orbital period 0.942 421 8 d Inclination 1.51° (to Saturn's equator) Satellite of Saturn Physical characteristics Dimensions 414.8×394.4×381.4 km (0.0311 Earths) Mean radius 198.30 ± 0.30 km Surface area ~490 000 km² Volume ~32 900 000 km3 Mass (3.749 3 ± 0.003 1) × 1019 kg (6.3 × 10−6 Earths) Mean density 1.147 9 ± 0.005 3 g/cm3 Equatorial surface gravity 0.063 6 m/s2 (0.648%g) Escape velocity 0.159 km/s Rotation period synchronous Axial tilt zero Albedo 0.962 ± 0.004 (geometric) Temperature ~64 K Apparent magnitude 12.9

The small moon Mimas passes in front of the larger moon Rhea, which is partly obscured by Saturn's rings, in this movie from NASAs Cassini spacecraft. Observations of mutual moon-crossing events, in which one moon passes close to or in front of another, help scientists refine their understanding of the orbits of Saturn's moons. This movie is a concatenation of 10 still images obtained over a span of about 6 minutes. The images were re-projected to a uniform view and computer interpolation was used to smooth the moons' motions between the frames. In this video, Mimas (396 kilometers, 246 miles across) moves in front of the rings. Rhea (1,528 kilometers, 949 miles across) reveals the delicate separations within the rings as the thin line of the F ring appears before the backdrop of the mid-southern latitudes of the moon. Mimas travels at an average speed of 14 kilometers per second (31,000 mph). Rhea's average speed is about 8 kilometers per second (18,000 mph). (For other movies like this one, see PIA11692 and PIA11693.) In this view Rhea, at a distance of approximately 2.7 million kilometers (1.7 million miles), is farther from Cassini than Mimas. Mimas is closer to the spacecraft at a distance of approximately 2 million kilometers (1.2 million miles). This view looks toward the northern, sunlit side of the rings from just above the ring plane. The images were taken in visible light with Cassinis narrow-angle camera on Oct. 19, 2009. The view was obtained at a Sun-Mimas-spacecraft, or phase, angle of 95 degrees. Scale on Mimas is 12 kilometers (7 miles) per pixel. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for the Science Mission Directorate at NASA Headquarters in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Mimas' shadow traverses the sunlit side of Saturn's rings in this movie and mosaic showcasing the unusual sights seen at Saturn as the planet approaches its August 2009 equinox. The novel illumination geometry created as the Saturnian system approaches equinox allows moons orbiting in or near the plane of Saturn's equatorial rings to cast shadows onto the rings. These scenes are possible only during the few months before and after Saturn's equinox which occurs only once in about 15 Earth years. Twenty images, each taken 3 minutes and 36 seconds apart, were combined to create this mosaic and movie. Contiguous images were stitched together to create the mosaic showing the whole swath of the rings across which the moon's shadow passed. At the beginning of the movie, the shadow starts on the bright B ring. It crosses the darker Cassini Division and then moves to the A ring. At the end of the movie, the edge of the shadow just catches the edge of the A ring next to blackness of the Roche Division separating the A ring from the thin F ring.

Saturn rings material believed to be formed from the debris of a moon of Saturn and Mimas a moon of Saturn badly cratered from a period of extensive asteroid collision with our solar system

In a silent orbital ballet, Saturn's crater-covered moon Rhea slips between the moons Mimas and Enceladus. The dark sides of Enceladus (bottom) and Mimas (top) are dimly illuminated by reflected light from Saturn. Rhea is 1,528 kilometers (949 miles) across, Mimas is 397 kilometers (247 miles) across, and Enceladus is 505 kilometers (314 miles) across. The movie was created using 59 clear-filter images taken over a period of about 40 minutes. The images were acquired by the Cassini spacecraft narrow-angle camera on Jan. 27, 2006, at a mean distance of approximately 3 million kilometers (1.9 million miles) from Rhea, 3.5 million kilometers (2.2 million miles) from Mimas, and 3.7 million kilometers (2.3 million miles) from Enceladus. The image scale is approximately 18 kilometers (11 miles) per pixel on Rhea, 21 kilometers (13 miles) per pixel on Mimas, and 22 kilometers (14 miles) per pixel on Enceladus.

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