The History Of Saturn

With a diameter of 74,900 miles, the only planet larger than Saturn is the planet Jupiter. The planet received its name from the Roman god of agriculture. To the Greeks, Saturn was known as “Cronus,” and was the father of the Zeus. As the sixth planet in the Solar System, the word Saturn is also derived from the word “Saturday.”

Even our prehistoric ancestors knew about the existence of Saturn, and it was the furthest known planet at that time. Galileo was able to observe Saturn in 1610, but could not explain the visible rings present around it. Dutch astronomer Christiaan Huygens is credited with explaining the structure of Saturn’s rings between 1655-1656. Huygens was also responsible for the discovery of Saturn’s moon Titan. More information was released about Saturn in 1675, when French astronomer Giovanni Domenico Cassini viewed the division between two rings of Saturn, and discovered they were not attached together.

The Orbit Of Saturn

The orbit of Saturn is elliptical, and the planet is slightly tilted 27 degrees from the perpendicular axis. The perihelion, or point at which the planet is closest to the sun, is approximately 838 million miles (1.3 billion km), whereas its aphelion, or the point at which the planet is farthest from the sun, is approximately 934 million miles (1.5 billion km).

The orbit of Saturn is very slow. It is able to complete a revolution around the sun in 10,759 Earth days or approximately 29-30 years on Earth. However, the rotation of Saturn is the second fastest of the planets, after Jupiter. Saturn is able to complete a day in 10 hours and 39 minutes. As a result of this fast rotation, the planet looks slightly flattened when viewed with a telescope. 

Expeditions To Saturn

Other than Mars, human beings have always been fascinated with the planet Saturn because of its appearance. However, distance and the structure of the planet, have contributed to only a few expeditions undertaken to gain more knowledge about the planet.

In 1974, the United States launched the Pioneer-Saturn spacecraft to visit Jupiter and Saturn. The spacecraft passed by within 13,000 miles of Saturn in 1979, and was able to take photographs of the planet.

The following expeditions to Saturn were launched in 1977 using the spacecrafts Voyager 1 and Voyager 2. Voyager 1 flew by Saturn in 1980, and Voyager 2 passed by in 1981. These spacecrafts were used to take photographs of the seventh ring of Saturn, while confirming the existence of nine of Saturn’s satellites. The Voyager 1 and Voyager 2 expeditions also sent back information on the nitrogenous atmosphere of Saturn’s satellite, Titan.

After this expedition, the United States launched the Cassini spacecraft in 1997. This mission was known as the Cassini-Huygens Mission, and contained the Cassini spacecraft contained a smaller probe called Huygens, sent by the European Space Agency. The purpose of the Huygens probe is to explore Titan, and it successfully landed on this satellite in January 2005.

The Cassini spacecraft was able to pass by the satellite Phoebe, and send back photographs of it. This mission was also responsible for confirming the presence of liquid water on the satellite Enceladus.

Overall, this expedition to Saturn by the Cassini spacecraft is suspected to end in 2008, when it has orbited the planet over seventy times. 

Exploring A Day On Saturn

A day on Saturn is a little longer than a day on Jupiter, with an average timeframe of 10 hours and 39 minutes. This fast rotational period is expected of Saturn as one of the gas planets, without any known solid surface. On exploration of Saturn, it would have all of the other characteristics similar to the other gas planets. One unique characteristic of Saturn is it is less dense than water, and would float. Saturn has its own magnetic field, which is much greater than the magnetic field of Earth. Due to the gaseous structure of Saturn, scientists do not believe that life exists on the planet.  

The planet’s atmosphere consists largely of hydrogen, with small amounts of helium, ammonia, and methane. Hydrogen is present in a concentration of 75 percent, while the concentration of other gases are 25 percent. Its structure can be broken down into three layers. The first layer a spacecraft would enter is a gaseous layer of hydrogen and helium, which has fused with the surrounding atmosphere. The second layer below this is a thick fluid layer of hydrogen and helium. The third layer, which surrounds the core of Saturn, is a layer of metallic hydrogen in a liquid form, similar to what is associated with Jupiter. The core is Saturn is believed to be solid material consisting of rock and iron, with high temperature reaching 21,150 degrees Fahrenheit.

Saturn does possess a dense cloud cover, which is arranged into different bands. The ‘banded’ is a result of the various gases present, and the variation in temperature on Saturn.

Another thing apparent while exploring Saturn is its temperature. The temperature of Saturn is colder than Earth because it is further away from the Sun. At the highest level of its cloud cover, the temperature is can be –285 degrees Fahrenheit at this layer. Higher warmer temperatures are found to the bottom of the cloud cover on Saturn. This variation in temperature is caused by the way the planet is tilted on its axis. Therefore, as seasons are apparent on Saturn, due to the uneven heating of the Northern and Southern hemispheres. However, a season on Saturn would last between 7 – 8 Earth years.   

In  1990, the Hubble Telescope was able to document the Great White Spot (GWS). This storm on Saturn was an area of swirling wind and gas as seen in the Great Red Spot on Jupiter. It is similar to the Earth’s hurricanes or tornados, and is able to spread to the entire surface of the planet in a couple of weeks.

The wind system on Saturn is quite active, with the wind reaching speeds of 1,000 miles per hour around the Equator. At the higher latitudes in the Northern hemisphere, the wind system alternates between an easterly and westerly direction, but blows in an easterly direction near the Equator.

Saturn is well known for its ring system. The rings are found around the Equator of Saturn, and consist of seven major rings. However, each of these seven major rings consists of smaller faint rings or ringlets. The ringlets are composed of ice and rock particles. The sizes of the particles vary from small regular size rocks on Earth to ice covered particles the size of more than 10 feet in diameter. The rings are labeled using the alphabet (A ring, B ring, C ring, etc.) in the order they were discovered.

The width of largest ring of Saturn is 180,000 miles. Major divisions or gaps exist within the ring system, with the widest being the Cassini Division (2,920 miles), existing between the A ring and B ring.

Table 1: The Ring System Of Saturn. (Space Today 2004)

The Satellites Of Saturn

There are 47 satellites associated with Saturn. At least 25 of these satellites have a diameter of 6 miles. The major moons of Saturn are described below.

Mimas

As the first moon of Saturn, Mimas is composed mostly of a small amount of rock and covered by water ice. It is not entirely spherical, and its surface is riddled with a number of impact craters and basins.

The most notable impact crater on Mimas is the Herschel Impact Crater. This impact crater covers 33 percent of Mimas’ surface, with a diameter approximately equal to 80 miles (130 km). Other than craters, the surface of Mimas also contains numerous chasms or steep valleys.

William Herschel discovered the satellite Mimas in September 1789. It has a diameter of 392 km and orbits Saturn every 23 hours.

Enceladus

Discovered in 1789, Enceladus is Saturn’s second moon. It is not as heavily cratered as Mimas, but does contain a few impact craters. It is highly reflective (100 percent), and is one of the brightest moons of Saturn.

The surface of Enceladus is quite varied. Enceladus is home to a number of smooth, flat plains, fissures, and rugged terrains. Craters located on this satellite are smaller than 35 km.

Enceladus also contains areas of water ice. With a diameter of 504 km, Enceladus orbits Saturn every 32.9 hours. 

Tethys

As the third moon of Saturn, Tethys was discovered by Cassini in 1684, and is larger than Enceladus. With a diameter of 1060 km, Tethys has a surface in which almost every area is covered with ice. There are two major landscapes seen on Tethys – impact craters, seen as light and dark areas from space – and valleys.

The largest impact crater on Tethys is Odysseus, which occupies 40 percent of the surface of Tethys. These craters are being slowly resurfaced by ice shifting.

The most prominent valley on Tethys is the Ithaca Chasma. It occupies a width of 100 km, and is approximately 2,000 km in length. With these measurements, the Ithaca Chasma is located on over 75 percent of the surface of Tethys.

Tethys is located a distance of 294,660 km from Saturn and orbits the planet every 1.89 days.

Dione

As the fourth satellite of Saturn, Dione is the third densest of all of Saturn’s moons. It is contains a surface similar to Tethys made up of craters with plains distributed throughout. However, Dione also contains bright ice cliffs. These ice cliffs are at least a hundred meters high.
With a diameter of 1123km, Dione orbits Saturn every 2.75 days.

Titan

As the sixth satellite Titan is the largest of Saturn’s satellites. With a diameter of 5,150 km only Jupiter’s satellite Ganymede is larger than it. It was discovered in 1655 by the astronomer Christiaan Huygens.

One of the most interesting features about Titan is the layer of thick haze surrounding it. From this, it has been discovered to be the only known satellite with its own atmosphere composed mostly of gases such as Nitrogen (98 percent), methane and carbon dioxide.

Titan is covered with a typography consisting mostly of water and rocks, which is relatively smooth. Information from the Huygens probe has revealed areas of hills and plains of ice “sand”. It also has other typography seen on Earth – volcanoes and sand dunes. The Cassini-Huygens mission revealed large sand dunes around Saturn’s equator.

Even though they have never been discovered, some scientists believe Titan might contain “seas” of liquid methane on its surface.  It orbits Saturn every 15. 9 days.

The common satellites, and their year of discovery, appear in the list below:

Table 2: The Common Satellites Of Saturn. (Space Today 2004)

Statistics About Saturn

Discovered By	Known by the Ancients
Date of Discovery	Unknown
Average Distance from the Sun	Metric: 1,426,725,400 km English: 885,904,700 miles Scientific Notation: 1.4267254 x 109 km (9.53707 A.U.) By Comparison: 9.53707 x Earth
Perihelion (closest)	Metric: 1,349,467,000 km English: 838,519,000 miles Scientific Notation: 1.349467 x 109 km (9.021 A.U.) By Comparison: 9.177 x Earth
Aphelion (farthest)	Metric: 1,503,983,000 km English: 934,530,000 miles Scientific Notation: 1.503983 x 109 km (10.054 A.U.) By Comparison: 9.886 x Earth
Equatorial Radius	Metric: 60,268 km English: 37,449 miles Scientific Notation: 6.0268 x 104 km By Comparison: 9.449 x Earth
Equatorial Circumference	Metric: 378,675 km English: 235,298 miles Scientific Notation: 3.78675 x 105 km
Volume	Metric: 827,130,000,000,000 km3 Scientific Notation: 8.2713 x 1014 km3 By Comparison: 763.6 x Earth
Mass	Metric: 568,510,000,000,000,000,000,000,000 kg Scientific Notation: 5.6851 x 1026 kg By Comparison: 95.16 x Earth
Density	Metric: 0.70 g/cm3 By Comparison: 0.127 x Earth
Surface Area	Metric: 43,466,000,000 km2 English: 16,782,000,000 square miles Scientific Notation: 4.3466 x 1010 km2 By Comparison: 85.22 x Earth
Equatorial Surface Gravity	Metric: 7.207 m/s2 English: 23.64 ft/s2 By Comparison: If you weigh 100 pounds on Earth, you would weigh 74 pounds on Saturn.
Escape Velocity	Metric: 127,760 km/h English: 79,390 mph Scientific Notation: 35,490 m/s By Comparison: Escape velocity of Earth is 25,022 mph.
Sidereal Rotation Period (Length of Day)	0.44401 Earth days 10.656 hours By Comparison: 0.445 x Earth
Sidereal Orbit Period (Length of Year)	29.4 Earth years 10755.7 Earth days
Mean Orbit Velocity	Metric: 34,821 km/h English: 21,637 mph Scientific Notation: 9,672.4 m/s By Comparison: 0.865 x Earth
Orbital Eccentricity	.0541506 By Comparison: 3.24 x Earth
Orbital Inclination to Ecliptic	2.484 degrees
Equatorial Inclination to Orbit	26.73 degrees By Comparison: 1.14 x Earth
Orbital Circumference	Metric: 8,725,000,000 km English: 5,421,000,000 miles Scientific Notation: 8.725 x 109 km By Comparison: 9.439 x Earth
Effective Temperature	Metric: -178 °C English: -288 °F Scientific Notation: 95 K
Atmospheric Constituents	Hydrogen, Helium Scientific Notation: H2, He By Comparison: Earth's atmosphere consists mostly of N2 and O2.
Table 3: Concise statistics on the planet Saturn (N.A.S.A. 2006)

References

Encyclopedia Britannica. “Saturn.” 2006. Encyclopedia Britannica Premium Service. 2006 http://www.britannica.com/eb/article-54286

National Aeronautics and Space Administration (N.A.S.A). “Saturn: Facts & Figures.” 2006 http://solarsystem.nasa.gov/planets/profile.cfm?
Object=Saturn&Display=Facts

Space Today Online. “Exploring Saturn.” 2004 http://www.spacetoday.org/SolSys/Saturn/SaturnHistory.html

Spinrad, Hyron. "Saturn." World Book Online Reference Center. 2004. World Book, Inc. http://www.nasa.gov/worldbook/saturn_worldbook.html

Saturn Images