Saturn's Major Moons Help
Saturn’s Major Moons—Titan
Saturn has more known natural satellites than any other planet. Most of Saturn’s moons are ice-covered orbs; the smaller ones are irregular chunks, some of which are doubtless asteroids that were captured by Saturn long after the planet and its main moon system were formed. Only five of Saturn’s moons exceed 1,000 km (620 mi) in diameter. These are Titan, Rhea, Iapetus, Dione , and Tethys .
The largest and most interesting satellite of Saturn is Titan, measuring 5,150 km (3,200 miles) in diameter. It is almost as large as Ganymede, Jupiter’s largest moon. Nevertheless, the gigantic, gaseous planet Saturn dwarfs it (Fig. 10-3). Titan is the only planetary moon that has a significant atmosphere. As viewed through the most powerful telescopes, and even from space probes flying by, Titan looks something like an orange little sister of Venus. The cloud layer is so thick that it hides the surface features from visual view.
The atmosphere of Titan is comprised mainly of nitrogen and methane and is cold by Earthly standards, far below 0°C at the surface. The atmospheric pressure at the surface is about half again as great as the normal atmospheric pressure at the surface of the Earth. Thus, although we would not be able to breathe Titan’s “air,” we would at least not have to worry about being crushed to death by its pressure, as would be the case on Venus.
The main reason scientists find Titan so interesting is that it contains an abundance of organic chemicals. The term organic does not mean that these chemicals were produced by or are necessarily indicative of living things in the environment. Methane and ethane, hydrocarbons similar to natural gas, are considered organic because they have the potential to give rise to amino acids under the right conditions. The impact of a large meteorite or comet or an electrical discharge caused by a thunderstorm creates the high temperatures necessary for the formation of amino acids, which are the building blocks of life.
Titan is a candidate for exploration by humans. The main problem to be overcome in such a visit, besides the enormous distance that separates the Saturnian system from Earth, is the powerful magnetic field surrounding Saturn, which accelerates subatomic particles from the Sun, producing intense belts of ionizing radiation. Although this radiation is less intense than that in the vicinity of Jupiter, it is still much greater than the intensity of the Van Allen radiation belts surrounding the Earth. Anyone who lands on Titan also would have to be prepared for the possibility of hitting a turbulent, liquid hydrocarbon surface, perhaps with floating icebergs of frozen methane and heavy methane rain or snow blowing down out of the red sky.
Rhea is 1,530 km (950 mi) in diameter. It orbits in an almost perfect circle 530,000 km (330,000 mi) from its parent planet. This moon is only a little more dense than water, and this fact has led astronomers to conclude that it must be comprised mainly of ice and very little rocky material.
Rhea, like most moons, keeps the same face toward Saturn at all times. As a result, one side of the moon “leads the way” through space, whereas the opposite side “trails behind.” There is a considerable difference in the appearance of the leading side of Rhea compared with the trailing side. The leading side is as densely packed with craters as any part of Earth’s moon, even though the surface of Rhea is mostly water ice. The trailing side has far fewer craters. This would be expected because the leading side would be more exposed to bombardment by meteorites.
Most of the rock in Rhea is believed to be contained in a small core. The moon’s small size and its relatively large distance from Saturn prevent heating from tidal effects, keeping the surface far below 0°C and hardening the ice so that it resembles granite and can maintain crater and mountain formations for a long time. Rhea has essentially no atmosphere.
Today on Education.com
- Coats and Car Seats: A Lethal Combination?
- Kindergarten Sight Words List
- Child Development Theories
- Signs Your Child Might Have Asperger's Syndrome
- 10 Fun Activities for Children with Autism
- Social Cognitive Theory
- Why is Play Important? Social and Emotional Development, Physical Development, Creative Development
- GED Math Practice Test 1
- The Homework Debate
- Problems With Standardized Testing