ScienceCasts: Don't Judge a Moon by its Cover
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Superficially, Saturn's moon Phoebe doesn't look much like a planet, but on the inside, the little gray moon has a lot in common with worlds like Earth.
Difference between regular and irregular moons Moons of the Solar System
10 Interesting Facts about Saturn
From the incredible low-density of Saturn to the famous “dragon storm”, we countdown 10 interesting Facts about Saturn!
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Top 10 interesting Facts about Saturn:
#10 It's the second-largest planet and sixth closest planet to the sun.
#9 There are 150 moons and moonlets.
#8 Saturn's moon Phoebe has a retrograde orbit
#7 Saturn is a low-density planet, mostly composed of hydrogen and helium, its density is even lower than water.
#6 The rings of Saturn are made up of innumerable water-ice particles or rock.
#5 A storm called the 'Dragon Storm' first appeared in 2004 and is still going on.
#4 A number of unmanned missions have taken place on the planet.
#3 It is normal for the wind speed to reach 1,800 kilometers per hour on Saturn.
#2 One year on Saturn is equal to 29.7 Earth years.
#1 Saturn is lovingly called The Jewel of the Solar System and it is easy to see why!
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A rare glimpse at Saturn's dark moon Phoebe
A rare glimpse at Saturn's dark moon Phoebe: Cassini captures incredible shot of the pockmarked satellite and makes it closest fly-by of Enceladus.
Phoebe (moon) - Video Learning - WizScience.com
"Phoebe" is an irregular satellite of Saturn a little over 200 km in diameter. It is thought to be a captured dwarf planet from the Kuiper belt that was battered out of hydrostatic equilibrium by repeated impacts, similar to how Vesta was battered out of hydrostatic equilibrium. It was discovered by William Henry Pickering on 17 March 1899 from photographic plates that had been taken starting on 16 August 1898 at the Boyden Observatory near Arequipa, Peru, by DeLisle Stewart. It was the first satellite to be discovered photographically.
Phoebe was the first target encountered upon the arrival of the "Cassini" spacecraft in the Saturn system in 2004, and is thus unusually well-studied for an irregular satellite of its size. "Cassini"s trajectory to Saturn and time of arrival were specifically chosen to permit this flyby. After the encounter and its insertion into orbit, "Cassini" would not go much beyond the orbit of Iapetus.
Phoebe was discovered by William Henry Pickering on 17 March 1899 from photographic plates that had been taken starting on 16 August 1898 at the Boyden Observatory near Arequipa, Peru, by DeLisle Stewart. It was the first satellite to be discovered photographically.
Phoebe was named after Phoebe, a Titan in Greek mythology that was associated with the Moon. It is also designated Saturn IX in some scientific literature. The IAU nomenclature standards have stated that features on Phoebe are to be named after characters in the Greek myth of Jason and the Argonauts. In 2005, the IAU officially named 24 craters .
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Latest pictures of Saturn from Cassini spacecraft
June 12, 2004
1. Still photos showing two views of Saturn's moon Phoebe
2. Still photo of moon Phoebe
3. Still photo of Saturn
4. Animation showing Cassini spacecraft's flyby of Phoebe
5. Animation showing Cassini's scheduled approach to Saturn
The internationally built Cassini spacecraft completed a flyby of Saturn's largest outer moon as it prepared to
enter a four-year orbit to study the ringed planet, according to NASA officials on Saturday.
Officials at the Jet Propulsion Laboratory said the plutonium-powered spacecraft, which is carrying 12 science instruments and a probe, came within about 1,285 miles (2068 kilometres) of the dark moon Phoebe on Friday.
The 3.3 (b) billion US dollar spacecraft pointed its instruments at the moon, then turned to point its antenna toward Earth. Its data reached NASA's Deep Space Network on Saturday morning.
Officials said the spacecraft was operating normally and was in excellent condition.
A crisp black-and-white photo of Phoebe released on Saturday looked somewhat like a skull with its overlapping shadows and craters.
Higher-resolution photos of the moon, which is just 137 miles (220.5 kilometres) across, are to be released later.
The spacecraft also transmitted data that scientists will examine to answer questions about Phoebe's mass and composition, said a member of Cassini's science team.
Scientist believe Phoebe originated in the outer reaches of the solar system but later hurtled toward Saturn, where it was captured by the planet's gravity.
With the flyby of Phoebe behind it, Cassini's next key manoeuvre is a trajectory correction scheduled for Wednesday to position the spacecraft to become a satellite.
The US-European craft is expected to enter Saturn's orbit on June 30 after it dashes through a gap in Saturn's rings.
Cassini will study Saturn, its rings and 31 known moons during its four-year orbit. Its two cameras could take as many as 500-thousand pictures.
Other probes have flown by the planet, but none have entered Saturn's orbit.
Cassini carries the Huygens probe, which is supplied by the European Space Agency and carries six instruments.
The probe, set to be released in December, is expected to land on Titan, Saturn's largest moon.
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Space probe Cassini sends back Saturn moon pictures
1. Wide of NASA Jet Propulsion Laboratory (JPL) press conference
2. SOUNDBITE: (English) Dr Torrence Johnson, Cassini Image Scientist, NASA JPL:
(overlaid with pictures of Phoebe, Saturn's small moon)
"Very heavily cratered drains, craters that are probably formed by other small Satunian satellites or objects coming from further out in the solar system to make those overlapping craters. Very old, four billion year old topography. One of the neat things that happened with these images, showing us the craters here on the right side, is we can see banding or layering. Several craters on this satellite have shown us, something that has been very difficult to find in pictures of an asteroid, and leads us to conclude rather complicated things going on in the surface geologically."
3. SOUNDBITE: (English) Dr Torrence Johnson, Cassini Image Scientist, NASA JPL:
(overlaid with pictures of Phoebe, Saturn's small moon)
"Now we pan over to the opposite slopes, also several miles high with materials streaming down. The really neat thing about this, is the very high contrast of these bright streamers, indicating we are probably seeing exposed ice."
4. Various images of Phoebe
5. SOUNDBITE: (English), Dr. Bonnie Baratti, Visual&Infrared Mapping Spectro., NASA JPL:
"Now, what does this all mean? Well this means that Phoebe is definitely not an astronaut. It did not form the asteroid belt because we don't see CO2 in the asteroid belt. It formed some place in the outer solar system, beyond the orbit of Jupiter, and as Dr. Johnson said, we believe that this is evidence that it came from the Kyper belt and was dragged into the saturnian system early in the formation of the solar systems. What we see is a very diverse body. We've mapped water ice, which seems to be associated with the right material, we have possibly simple hydro carbons, we have found carbon dioxide. This has never been found on a small body of this sort. Unlike asteroids, Phoebe is very, very variegated. It doesn't have a bland surface at all."
6. NASA images of Phoebe
7. NASA animation of Cassini spacecraft flying towards Saturn
Scientists at NASA's Jet Propulsion Labaratory (JPL) in the US state of California said on Wednesday that Saturn's moon Phoebe, is likely to be a primordial mixture of ice, rock and carbon-containing compounds.
According to scientists, bodies like Phoebe were plentiful in the outer reaches of the solar system about four and a half (b) billion years ago.
The scientists reviewed data from the Cassini spacecraft's flyby of the diminutive moon, carried out on 11 June.
In addition,a composite infrared spectrometer was used to generate temperature maps.
The maps depict the surface of Phoebe as being very cold, only about 110 degrees above absolute zero (minus 163 degrees Celsius, or minus 261 degrees Fahrenheit).
The Cassini spacecraft is part of a joint mission between NASA, the European Space Agency, and the Italian Space Agency.
The spacecraft was launched from the Kennedy Space Centre in Florida on 15 October 1997.
It is expected to reach the Saturnian region in July 2004.
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Douglas Hamilton: Small particles dominate Saturn’s Phoebe ring to surprisingly large distances
Douglas Hamilton talks to Sciencevideos.org about his recent publication 'Small particles dominate Saturn’s Phoebe ring to surprisingly large distances'
Saturn’s Faint Outer Ring Is Massive
Astronomers have recently been able to calculate the size of Saturn’s faint outer ring named Phoebe, and it is massive at 30 percent larger than originally estimated.
Saturn is known for its distinctive planetary rings, but not all of them are easily seen.
In 2009 a massive yet invisible one was discovered, and though scientists knew it was huge, they didn’t know the full extent of its size. Now they do.
According to a recent study, the outer ring known as Phoebe is about 30 percent bigger than calculations had estimated.
One scientist reports that it is "more than 200 times as big across as Saturn itself. It's absolutely immense, much bigger than any other ring that we know of."
It is also extremely far from its parent planet, about 3.75 million miles away, which means particles and everything else that enters its domain move incredibly slowly.
Those contents, in addition to not traveling very fast, are tiny and sparsely distributed, so passing through the ring in a spaceship would be uneventful.
One of the main reasons astronomers even realized Phoebe existed in 2009 is because one of Saturn’s moons, Iapetus, was black on one side and white on the other.
Based on images from a NASA's telescope, they were able to see that the leading face of the moon was dark because it was picking up particles as it traveled through Phoebe’s ring.
Saturn Family Tour
This video showcases the Saturnian system, beginning with the planet itself and panning out to its newest addition -- an enormous ring discovered in infrared light by NASA's Spitzer Space Telescope.
The view starts with a simulated view of Saturn. It then moves outward, showing the orbits of many of Saturn's inner moons in green. The white lines show outer moons with orbits of varying inclinations.
The yellow line shows the orbit of the moon Phoebe, which circles through the newfound ring, represented in tan. Both Phoebe and the outer ring orbit at an angle of 27 degrees from the main ring plane (they also orbit in the opposite direction of the other rings and most of the moons).
The movie then zooms back into the system to show the orbit of the moon Iapetus in blue. Astronomers think that material from the outer ring is migrating in toward Iapetus, splattering its leading hemisphere. This would explain the moon's strange half-black, half-white appearance, first noted by Giovanni Cassini in the late seventeenth century.
Elements of this animation are courtesy SCISS in Sweden, and American Museum of Natural History in New York, New York.
Saturn Moon - Phoebe - 20 real pictures youtube.com/MoonMonde
Saturn Moon - Phoebe - 20 real pictures youtube.com/MoonMonde
Saturn's Moon Phoebe is Much Like a Planet | NASA Cassini Mission HD Video
Visit my website at http://www.junglejoel.com - although small and battered, Saturn's moon, Phoebe has many planet-like qualities. Please rate and comment, thanks!
Saturn's Oddball Moon Phoebe Seems Planet-Like | Video
Known for its backwards orbit around Saturn and its unusual shape, Phoebe was once nearly spherical and has dense rock "core" material near its center, characteristics of a planet.
Phoebe and Titan orbiting Saturn (polar view)
Phoebe (smaller white moon) and Titan (orange moon) orbiting Saturn, as seen from a position above Saturn's north pole. Phoebe's orbit is noticeably non-circular (eccentric), and opposite to Titan's.
Phoebe and Titan orbiting Saturn (equatorial view)
Phoebe (smaller white moon) and Titan (orange moon) orbiting Saturn, as seen from a position aligned with Saturn's equator. Note that Phoebe orbits the opposite direction as Titan; this is because it probably didn't form at the same time as Saturn.
Solar System shapes and sizes
A comparison of the shapes and rotations of three Solar System bodies: Phoebe (left ), Vesta (center), and Mimas (right). Vesta is the second most massive object in the main asteroid belt, while Phoebe and Mimas are both moons of Saturn. Mimas has a diameter of 416 kilometers along its longest axis. I chose to order the objects by roundness, with Phoebe the most irregular and Mimas closest in shape to an ellipsoid. As the smallest body in this comparison, Phoebe's irregular shape isn't a surprise. Mimas is rounder than Vesta despite being significantly smaller--a colossal pair of impacts at Vesta's south pole is partly responsible for the asteroid's distinctive shape.
The orientation and rotation rates of all objects are accurate, with 'up' matching the direction of the Earth's north pole. Vesta rotates quickly, completing a rotation about once every five hours. Like our own moon, Mimas is in a synchronous rotation state, with a rotation period matching its orbital period of 22.6 hours. Phoebe is one of the rare moons that is not a synchronous rotator and has a swift--by moon standards--rotation period of about 9 hours.
The 3D shape models used in this visualization were derived from spacecraft imagery by Robert Gaskell.
Phoebe Shape Model
Saturn's moon Phoebe rendered with self-shadowing. The shape model was derived by Robert Gaskell from Cassini image data.
Saturn's Outermost Phoebe Ring in HD by NASA, Spitzer Telescope
Curiosity Shop of Saturn's Moons
This video is modeled in the classic tradition of P.T. Barnum, offering a collection of oddities for your viewing pleasure. So enter the Curiosity Shop for a compilation of facts and beautiful moon images taken by the Cassini spacecraft in orbit around Saturn since 2004, set to Edvard Grieg's Piano Concerto in A Minor, Op. 16 II. Adagio. This video is produced in honor of the recent Cassini Spacecraft Mission extension through September 2017.
Take a gander at Gigantic Titan to your left. Feel free to ogle bright Enceladus to your right, reflecting close to 100 percent of the light that hits its surface. Don't be afraid to eyeball Mimas and her craters. That's what she's there for! Saturn has the second most moons of planets in the solar system. Second, only to Jupiter.
September 27th, 2010 marked the end of the Cassini Equinox Mission, which was over the last 2 years, and the beginning of the Cassini Solstice Mission. The extension to takes the spacecraft to September 2017, a couple months past Saturn's Northern summer solstice in May 2017. Cassini has done a great deal to extend our knowledge of Saturn and it's moons as well as delivered some of the most gorgeous photos taken in the Solar System; Photos of Saturn, Saturn's rings and Saturn's moons. This video pictures just a few of the many photos.
Diameter: averages 396 km
Orbital Radius: 185,520 km
Orbital Period: 22 hours and 37 minutes
Mass: 37,500,000,000 megatonnes
Mimas and Rhea are widely considered the most heavily cratered bodies in the Solar System
Diameter: about 500 km
Orbital Radius: 238,020 kilometers
Orbital Period: 1.37 Days
Mass: 70,000,000,000 megatonnes
It is postulated that Enceladus is heated by a tidal mechanism similar to Jupiter's moon Io and many signs point to a liquid core even though it should've frozen aeons ago.
It is the most reflective object in the solar system.
Diameter: 1,066 km
Orbital Radius: 294,660km
Orbital Period: 1.89 earth days
Mass: 627,000,000,000 megatonnes
Odysseus Crater (named for a Greek warrior king in Homer's two great works, The Iliad and The Odyssey) dominates the Tethyan western hemisphere. Odysseus Crater is 400 kilometers in-diameter (almost 250 miles). That diameter is nearly two-fifths of Tethys itself.
Diameter: 1,123 km
Orbital Radius: 377,400 km
Orbital Period: 2.7 earth days
Mass: 1,100,000,000,000 megatonnes
Cassini showed Dione's bright wisps to be bright canyon ice walls (some of them several hundred meters high), probably caused by subsidence cracking. The walls are bright because darker material falls off them, exposing bright water ice.
Diameter: 1,528 km
Average Distance: 527,040 km
Orbital Period: 4.52 Earth days
Mass: 2,310,000,000,000 megatonnes
Equatorial Radius: 2,575 km
Orbital Distance: 1,221,830 km
Orbital Period: 15.95 Earth days
Mass: 134,550,000,000,000 megatonnes
Recent results from the Cassini mission suggest that hydrogen and acetylene are depleted at the surface of Titan. Both results are still preliminary, but the findings are interesting for astrobiology. A paper published 5 years ago suggested that methane-based (rather than water-based) life -- ie, organisms called methanogens -- on Titan could consume hydrogen, acetylene, and ethane. The measured depletion of these compounds could mean the existence of these life forms on the surface.
Average diameter: 270 km
Mass: 800,000,000 megatonnes
Orbital Distance: 1,481,100 km
Orbital Period: 21.28 Earth days
Hyperion is the largest known irregular (nonspherical) body in the Solar System.
Equatorial Radius: 735.5 km
Orbital Distance: 3,561,300 km
Orbital Period: 79.33 Earth days
Mass: 1,600,000,000,000 megatonnes
The September 2007 Cassini flyby of Iapetus showed that thermal segregation is probably the most responsible for Iapetus having a darker hemisphere. Iapetus has a very slow rotation, longer than 79 days. Such a slow rotation means that the daily temperature cycle is very long, so long that the dark material can absorb heat from the Sun and warm up.
Diameter: 220 km
Orbital Distance: 12,952,000 km
Orbital Period: about 18 months
Mass: 400,000,000 megatonnes
Unlike most major moons orbiting Saturn, Phoebe is very dark and reflects only 6 percent of the sunlight it receives. Its darkness and irregular, retrograde orbit suggest Phoebe is most likely a captured object.
The moons of Saturn are numerous and diverse, ranging from tiny moonlets to the enormous Titan. Saturn has 66 moons with confirmed orbits, 53 of which have names, and most of which are quite small. With seven moons that are large enough to have sufficient gravitational attraction to become spherical in shape in addition to the planet's broad and dense rings, the Saturnian system is the most diverse in the solar system. Particularly notable are Titan, the second largest moon in the Solar System, with an earth-like atmosphere and a landscape including hydrocarbon lakes and dry river networks, and Enceladus, which emits jets of gas and dust and may harbor liquid water under its south pole region.
Twenty-three of Saturn's moons are regular satellites, with prograde orbits that are not greatly inclined with respect to Saturn's equatorial plane. In addition to the seven major satellites, four moons are small trojans that share an orbit with a larger moon, and two more are mutually co-orbital moons. Further two moons are shepherds of Saturn's F Ring. Two moons are known to orbit within gaps in Saturn's rings. A relatively large Hyperion is lock in a resonance with Titan. The remaining moons orbit near the outer edge of the A Ring, within G Ring and between Mimas and Enceladus. The regular satellites are traditionally named after Titans and Titanesses or other figures associated with the mythological Saturn.
The remaining forty-three, all except one small, are irregular satellites, whose orbits are much farther from Saturn, have high inclinations, and are mixed between prograde and retrograde. These moons were likely captured minor planets, or debris from the breakup of such bodies after they were captured, creating collisional families. The irregular satellites have been classified by their orbital characteristics into Inuit, Norse, and Gallic groups, and their names are chosen from the corresponding mythologies. The largest of the irregular moons is Phoebe—the ninth moons of Saturn discovered at the end of nineteenth century.
The rings of Saturn are made up of icy objects ranging in size from microscopic to hundreds of metres, each of which is on its own orbit about the planet. Thus a precise number of Saturnian moons cannot be given, as there is no objective boundary between the countless small anonymous objects that form Saturn's ring system and the larger objects that have been named as moons. At least 150 moonlets embedded in the rings have been detected by the disturbance they create in the surrounding ring material, though this is thought to be only a small sample of the total population of such objects.
Saturn's Moon: Phoebe Rotation
Phoebe is an irregular satellite of Saturn. It was discovered by William Henry Pickering on 17 March 1899 from photographic plates that had been taken starting on 16 August 1898 at Arequipa, Peru by DeLisle Stewart. It was the first satellite to be discovered photographically.
Phoebe was the first target encountered upon the arrival of CassiniHuygens to the Saturn system in 2004, and is thus unusually well-studied for a natural satellite of its size. Cassini's trajectory to Saturn and time of arrival were specifically chosen to permit this flyby. After the encounter and its insertion orbit, Cassini would not go much beyond the orbit of Iapetus.
The moon is named after Phoebe, a Titan in Greek mythology. It is also designated Saturn IX. The IAU nomenclature standards have stated that features on Phoebe are to be named after characters in the Greek myth of Jason and the Argonauts. In 2005, the IAU officially named 24 craters (Acastus, Admetus, Amphion, Butes, Calais, Canthus, Clytius, Erginus, Euphemus, Eurydamas, Eurytion, Eurytus, Hylas, Idmon, Iphitus, Jason, Mopsus, Nauplius, Oileus, Peleus, Phlias, Talaus, Telamon, and Zetes).
Dr. Toby Owen of the University of Hawaii at Manoa, chairman of the International Astronomical Union Outer Solar System Task Group said:
"We picked the legend of the Argonauts for Phoebe as it has some resonance with the exploration of the Saturn system by Cassini-Huygens. We can't say that our participating scientists include heroes like Hercules and Atalanta, but they do represent a wide, international spectrum of outstanding people who were willing to take the risk of joining this voyage to a distant realm in hopes of bringing back a grand prize."
For more than 100 years, Phoebe was Saturn's outermost known moon, until the discovery of several smaller moons in 2000. Phoebe is almost 4 times more distant from Saturn than its nearest major neighbor (Iapetus), and is substantially larger than any of the other moons orbiting planets at comparable distances.
All of Saturn's moons up to Iapetus orbit very nearly in the plane of Saturn's equator. The outer irregular satellites follow fairly to highly eccentric orbits, and none is expected to rotate synchronously as all the inner moons of Saturn do (except for Hyperion). See Saturn's satellites families.
Phoebe is roughly spherical and has a diameter of 220 kilometres (140 mi), which is equal to about one-fifteenth of the diameter of Earth's moon. Phoebe rotates on its axis every nine hours and it completes a full orbit around Saturn in about 18 months. Its surface temperature is 75 K (-198°C).
Most of Saturn's inner moons have very bright surfaces, but Phoebe's albedo is very low (0.06), as dark as lampblack. The Phoebean surface is extremely heavily scarred, with craters up to 80 kilometres across, one of which has walls 16 kilometres high.
Phoebe's dark coloring initially led to scientists surmising that it was a captured asteroid, as it resembled the common class of dark carbonaceous asteroids. These are chemically very primitive and are thought to be composed of original solids that condensed out of the solar nebula with little modification since then.
However, images from the Cassini-Huygens space probe indicate that Phoebe's craters show a considerable variation in brightness, which indicate the presence of large quantities of ice below a relatively thin blanket of dark surface deposits some 300 to 500 metres (980 to 1,600 ft) thick. In addition, quantities of carbon dioxide have been detected on the surface, a finding which has never been replicated on an asteroid. It is estimated that Phoebe is about 50% rock, as opposed to the 35% or so that typifies Saturn's inner moons. For these reasons, scientists are coming to believe that Phoebe is in fact a captured Centaur, one of a number of icy planetoids from the Kuiper belt that orbit the Sun between Jupiter and Neptune. Phoebe is the first such object to be imaged as.
Discovered by W.H. Pickering
Discovery date 17 March 1899 / 16 August 1898
Alternate name Saturn IX
Semi-major axis 12 955 759 km
Eccentricity 0.156 241 5
Orbital period 550.564 636 d
Inclination 173.04° (to the ecliptic)
151.78° (to Saturn's equator)
Satellite of Saturn
Dimensions 230 x 220 x 210 km
Mean radius 106.60 ± 1.00 km
Mass (0.829 2 ± 0.001 0) × 1019 kg
Mean density 1.634 2 ± 0.046 0 g/cm³
Equatorial surface gravity ~0.049 m/s2
Escape velocity ~0.10 km/s
period 0.386 75 d (9 h 16 min 55.2 s)
Axial tilt 152.14°