The Cassini spacecraft was a project launched by NASA, the European Space Agency and the Italian Space Agency that has yielded large amounts of useful data and many beautiful pictures. This one in particular shows the C ring on the right, and the B on the left. The red hues indicate dirty particles and blue the cleaner ice. The rings of Saturn are labelled from the inside out with rings, D, C, B, and A, followed by F, G, and E. In order to image the rings in such quality the Cassini spacecraft used its Ultraviolet Imaging Spectrograph in resolution some 100 times that of the Voyager 2 spacecraft.
Rhea, the second largest moon of Saturn, is a dirty snowball of rock and ice. The only moon with an oxygen atmosphere, thin though it may be, Rhea is one of the most heavily cratered satellites in the solar system.
A very faint oxygen atmosphere exists around Rhea, the first direct evidence of an oxygen atmosphere on a body other than Earth. The atmosphere is thin, with oxygen measuring about 5 trillion times less dense than that found on Earth. Oxygen could be released as the surface is irradiated by ions from Saturn’s magnetosphere. The source of the carbon dioxide is less clear, but could be the result of similar irradiation, or from dry ice much like comets.
On March 6, 2008, NASA announced that Rhea may have a tenuous ring system. This would mark the first discovery of rings about a moon. The rings’ existence was inferred by observed changes in the flow of electrons trapped by Saturn’s magnetic field as Cassini passed by Rhea. Dust and debris could extend out to Rhea’s Hill sphere, but were thought to be denser nearer the moon, with three narrow rings of higher density. The case for a ring was strengthened by the subsequent finding of the presence of a set of small ultraviolet-bright spots distributed along Rhea’s equator (interpreted as the impact points of deorbiting ring material).However, when Cassini made targeted observations of the putative ring plane from several angles, no evidence of ring material was found, but there’s still something around Rhea that is causing a strange, symmetrical structure in the charged-particle environment around Saturn’s second-largest moon.
Titan is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found
Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan’s surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in Titan’s polar regions.
The atmosphere is largely nitrogen; minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. Titan’s lower gravity means that its atmosphere is far more extended than Earth’s and about 1.19 times as massive. It supports opaque haze layers that block most visible light from the Sun and other sources and renders Titan’s surface features obscure.Atmospheric methane creates a greenhouse effect on Titan’s surface, without which Titan would be far colder. Conversely, haze in Titan’s atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, cancelling a portion of the greenhouse effect warming and making its surface significantly colder than its upper atmosphere.
Titan’s clouds, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating the overall haze.The findings of the Huygens probe indicate that Titan’s atmosphere periodically rains liquid methane and other organic compounds onto its surface. Clouds typically cover 1% of Titan’s disk, though outburst events have been observed in which the cloud cover rapidly expands to as much as 8%. One hypothesis asserts that the southern clouds are formed when heightened levels of sunlight during the southern summer generate uplift in the atmosphere, resulting in convection. This explanation is complicated by the fact that cloud formation has been observed not only after the southern summer solstice but also during mid-spring.
With the sun now shining down over the north pole of Saturn’s moon Titan, a little luck with the weather, and trajectories that put the spacecraft into optimal viewing positions, NASA’s Cassini spacecraft has obtained new pictures of the liquid methane and ethane seas and lakes that…
Our solar system is huge, so let us break it down for you. Here are 5 things you should know this week:
1. From Pluto, with Love
Last Valentine’s Day, no one had even seen Pluto’s most famous feature, the heart-shaped Sputnik Planum. These days, the New Horizons spacecraft is sending more and more pictures back to Earth from its Pluto flyby last July. We received new ones almost on a weekly basis. For the latest love from the outer solar system, go HERE.
2. Saturn’s Rings: More (and Less) than Meets the Eye
The Cassini spacecraft is executing a series of maneuvers to raise its orbit above the plane of Saturn’s famous rings. This will offer some breathtaking views that you won’t want to miss. Meanwhile, Cassini scientists are learning surprising things, such as the fact that the most opaque sections of the rings are not necessarily the thickest.
3. Stay on Target
The Juno spacecraft recently completed a course correction maneuver to fine-tune its approach to Jupiter. After years of flight and millions of miles crossed, arrival time is now set to the minute: July 4th at 11:18 p.m. EST. See why we’re going to jupiter HERE.
4. The Many Lives of “Planet X”
The announcement of a potential new planet beyond Neptune creates an opportunity to look back at the ongoing search for new worlds in the unmapped reaches of our own solar system. Review what we’ve found so far, and what else might be out there HERE.
5. Answering the Call of Europa
There are a few places more intriguing that Jupiter’s icy moon, Europa, home to an underground ocean with all the ingredients necessary for potential life. We’re undertaking a new mission to investigate, and the project’s top manager and scientist will be giving a live lecture to detail their plans. Join Barry Goldstein and Bob Pappalardo on Feb. 11 at 10 p.m. EST for a live lecture series on Ustream.
Want to learn more? Read our full list of the 10 things to know this week HERE.
Saturn’s largest and second largest moons, Titan and Rhea, appear to be stacked on top of each other in this true-color scene from NASA’s Cassini spacecraft.
Titan is likely differentiated into several layers with a 3,400-kilometre (2,100 mi) rocky center surrounded by several layers composed of different crystal forms of ice.Its interior may still be hot and there may be a liquid layer consisting of a “magma” composed of water and ammonia between the ice Ih crust and deeper ice layers made of high-pressure forms of ice.
Rhea is an ice-cold body of weak density (1.236 g/cm3), indicating that the moon consists of a rocky nucleus counting only for a third of the mass of Rhea, the rest being mainly some ice-cold water.