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Note: You can click on each image below to view a larger version.
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Saturn is the second largest planet in the solar system, and is famous for its rings. These
consist of thousands of small pieces of rock and ice orbiting the planet and are divided
into many concentric rings, with gaps of varying size between them. |
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In fact, all the gas giants have rings. Jupiter has a faint band of debris just above
the cloud tops, while Uranus and Neptune have extensive rings of
dark material which for obvious reasons are very hard to see.
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This
Voyager 2 image shows the two most prominent gaps in the rings, known as the Cassini division and Encke division
after the astronomers who discovered them. The Cassini division is the large gap in the middle of the rings, and
the Encke division is the thin gap near the outside edge. |
It is believed that these areas are swept clean of material by the gravitational pull of some of Saturn's moons.
Saturn consists of approximately 75% hydrogen with most of the rest being helium, and is thought to have a similar
internal structure to Jupiter. Its clouds are as full of activity as Jupiter's, but they look much blander
because the detail is obscured by a layer of haze high in the atmosphere.
Saturn and its moons |
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Titan |
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Iapetus |
ABOVE LEFT: A montage of photos of Saturn and its moons - Dione (in the forefront), Tethys (to the right of Dione),
Mimas (to the right of and above Tethys), Enceladus (to the left of Dione), Rhea (to the left of and above Enceladus),
and Titan (top-right corner).
Titan is the largest moon of Saturn, with a dense atmosphere consisting mostly of nitrogen at high altitudes with
high concentrations of methane in the lower levels. At the surface the atmospheric pressure is 50% greater than here on Earth, with a temperature of
about -179C. The thick haze in the upper atmosphere made it impossible to see the surface from space, so little was
known about it until January 14th 2005, when a lander called
Huygens
was dropped onto Titan from the
Cassini
space probe, which has been orbiting Saturn since July 2004.
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The picture from Huygens at left shows a surface of frozen hydrocarbons scattered with "rocks" of
water ice, whose rounded shapes suggest that they have been subject to erosion from flowing liquids.
Titan
appears to be a world where methane rain falls regularly, cutting
channels
through the high ground as it
flows down to dark flood plains dotted with ice islands.
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Iapetus is another interesting moon, since one hemisphere appears to be covered with bright ice, while the other is a
dusty black. It is not clear whether this is due to some internal geological process or to something falling
onto the surface from space, although it is hoped that data and
images
from Cassini will settle the issue.
However in the novel of the film
2001, Arthur C. Clarke put it down to the mysterious black monolith that was sited there...
To see Saturn as anything other than a star-like point a telescope is needed. However, the movements of Titan
can be followed with a pair of binoculars.
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