Astronomy - Planet Saturn
Mass: 5.688 X 1026 kg (95.18 Earths)
Radius (equatorial): 60 268 km
Mean density: 0.69 g/cm3
Distance from Sun: 1 429 400 000 km
Rotational period: 10.233 hours
Orbital period: 29.458 years
Escape velocity: 35.49 km s-1
Apparent magnitude: 0.67
Surface temperature: -125°C (cloud)
Atmosphere composition: hydrogen (97%), helium (3%)
Number of satellites: 34 (Titan, Iapetus, Rhea, Dione, Tethys etc.)
The planet Saturn is second largest in terms of size in the Solar System. It is famously known due to its spectacular appearance of ring systems.
However, Saturn has been known since prehistoric times and in Roman mythology the planet is the god of agriculture. Nevertheless, the unusual feature of the planet was not
realised until the year 1610 when Galileo first observed the planet with a telescope, his new invention. Saturn remained the only planet known to possess the ring until 1977 when
rings were also discovered around Uranus, Jupiter and Neptune. However, these rings are very faint and thin when compare with that of Saturn. The rings are made mainly of small rocky materials
coated with reflective water ice. Close inspection of the rings reveal hundreds of distinguishable smaller bands with gaps in-between. The most prominant gap, is called the Cassini Gap or Division.
It is named after the French-Italian Astronomer Jean-Dominique Cassini who discovered the gap. The gap is large enough to be visible even from Earth telescopes (see picture above).
Saturn was first visited by the NASA space probe, Pioneer 11 and then followed by Voyager 1 and 2. At the time of this writing, the Cassini space probe, which arrived in July 2004,
is currently orbiting the planet systems. Like Jupiter, Saturn is a gas giant which composed mainly of hydrogen and helium. The density of the planet is very small and coupled with its rapid rotation, the spherical shape of the planet appears squashed (oblate),
as the picture shown above.
Saturn has more than 34 satellites. These bodies are usually very small. The only notably large satellite is Titan, which is also visible in a small telescope. In space, it appears as a large, featureless orange blob,
due to its extremely thick atmospheric cloud that completely shrouds the surface feature beneath. There is a great deal of interest to study Titan not only becuase it is the only satellite that contains significant amount
of atmosphere but also its meteorological system is thought to be comparable to that of primodial Earth. Its atmosphere consists largely of nitrogen, argon and methane. with a surface temperature of less than -175 degree C, no water vapour is expected to exist in atmosphere.
Instead, vapour and liquid system of unusual kind is thought to exist, such as ethane and methane oceans and lakes, that weathers the surface.
This mosaic image of Saturn is considered to be the most detailed and natural colored global view of the planet. The mosaic is composed of 126 images taken by the Cassini space probe in October 2004,
about 6.3 million km from the planet.
Credit: NASA/JPL/Space Science Institute
Mosiac image of Saturn's splendour ring system showing its intricacies, complexities, gravitational resonance and wave patterns. Six images were aquired to create this natural-colored mosaic by the
Cassini space probe from a distance of 1.8 million km, in December 2004.
Credit:NASA/JPL/Space Science Institute
A natural color image of the surface of Titan, returned by the Huygen space probe as it landed on the moon in January 2004.
Initially thought to be rocks or ice blocks, they are more pebble-sized. The surface is thought to consist of a mixture of
water and hydrocarbon ice. There is also evidence of erosion at the base of these objects, indicating possible fluid-like activity.
Credit: ESA/NASA/JPL/University of Arizona
Cassini-Huygen Mission - Current mission to Saturn (NASA page)
Huygen-Titan Mission - More details on Huygen Space probe descend and Titan.