0-Saturn and Friends.jpgSaturn and His Moons192 visiteThe dozens of moons orbiting Saturn vary drastically in shape, size, age and origin. Some of these moons have rocky surfaces, while others are porous, icy bodies. Many have craters, ridges and valleys and some show evidence of tectonic activity. Some appear to have formed billions of years ago, while others appear to be pieces of a bigger, fragmented body. The most interesting one is Titan, the biggest of them all. Larger than Earth's Moon, Titan even has its own thick atmosphere - the only natural satellite in the Solar System with such a luxury. During its 4-year mission in this immense region, the Cassini spacecraft will extensively photograph many of these moons and collect data that will increase our understanding of their composition.
To date, 34 moons have been officially named. In alphabetic order, they are: Albiorix, Atlas, Calypso, Dione , Enceladus, Epimetheus, Erriapo, Helene, Hyperion, Iapetus, Ijiraq, Janus, Kiviuq, Methone, Mimas, Mundilfari, Narvi, Paaliaq, Pallene, Pan, Pandora, Phoebe, Polydeuces, Prometheus, Rhea, Siarnaq, Skadi, Suttung, Tarvos, Telesto, Tethys, Thrym, Titan and Ymir.
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Janus-PIA07529.jpgJanus from 357.000 Km54 visiteThis close-up look at Saturn's moon Janus reveals spots on the moon's surface which may be dark material, maybe exposed by impacts. If the dark markings within bright terrain are indeed impact features, then Janus' surface represents a contrast with that of Saturn's moon Phoebe, where impacts have uncovered bright material beneath a darker overlying layer. Recent theories say also that Janus may be a porous body, composed mostly of water ice.
This image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 20, 2005, at a distance of approx. 357.000 Km (about 222.000 miles) from Janus and at a Sun-Janus-spacecraft, or phase, angle of 6°. Resolution in the original image was 2 Km (about 1,3 miles) per pixel. The view was magnified by a factor of two and contrast-enhanced to aid visibility of the moon's surface".
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Japetus-Orbit-00.jpgSide view of Japetus's orbit68 visiteThe orbit of Japetus is somewhat unusual. Although it is Saturn's third-largest moon, it orbits much farther from Saturn than the next closest major moon, Titan. It has also the most inclined Orbital Plane of the regular satellites; only the irregular outer satellites like Phoebe have more inclined orbits. The cause of this is unknown.
Because of this distant, inclined orbit, Japetus is the only large moon from which the Rings of Saturn would be clearly visible; from the other inner moons, the Rings would be edge-on and difficult to see.MareKromium
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Japetus-temp.2-PIA07005_modest.jpgJapetus Temperature Map52 visiteCaption NASA originale:"Temperatures reach nearly 130 Kelvin (-226 F) at noon on the equator on the dark material that covers most of this side of Japetus, making high noon on Japetus's dark side probably the warmest place in the Saturn System. This is much warmer than temperatures on the moon Phoebe - as measured by the composite infrared spectrometer in June 2004 - which peaked near 112 Kelvin (-258 F). That's because, although Phoebe is almost as dark as Japetus's dark material and absorbs nearly as much sunlight, Phoebe rotates much more quickly (once every 9 hours, compared to 79 days for Japetus). That means the surface has less time to heat up during the day. Temperatures on Japetus' bright material are much colder, peaking near 100 Kelvin (-280 F), both because the bright material absorbs less sunlight and because it is further from the equator on this side of Japetus".
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PHOEBE-PIA06064_modest.jpgPhoebe from Cassini-Huygens78 visiteUn'immagine spettacolare che ci mostra questa Luna martoriata da impatti occorsi - forse - milioni o miliardi di anni fa. La sua forma vagamente ovoidale, unita alle sue caratteristiche superficiali, fanno assomigliare questa Luna Maggiore - secondo noi - a Phobos. La grande depressione che vedete sulla parte superiore di Phoebe, infine, ci ricorda proprio lo "Stickney Crater" di Phobos
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PHOEBE-PIA06064_modest.jpgPhoebe (Extremely Ehnanced and Saturated Natural Colors; credits: Lunexit Team)53 visitenessun commentoMareKromium
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PHOEBE-PIA06067_modest.jpgPhoebe - closing up68 visitenessun commento
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PHOEBE-PIA06068_modest.jpgPhoebe's Fly-By (1)81 visitenessun commento
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