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Saturn's Moon, Enceladus: Facts, Lesson & Quiz

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Jeff Fennell

Jeff has a master's in engineering and has taught Earth science both domestically and internationally.

Enceladus is the sixth-largest moon in Saturn's orbit. It is interesting to astronomers because there is believed to be tectonic activity on the moon. This lesson will cover the facts of Enceladus.

Enceladus

Of Saturn's 62 moons, Enceladus is the sixth largest with a diameter of 505 kilometers. Though it is one of Saturn's largest moons, it is still relatively small. It's only one-seventh the diameter of Earth's moon and is small enough to fit inside the borders of the state of Arizona or Colorado.

Even though its size is relatively small, the surface of Enceladus is almost completely covered with ice, which reflects more than 90% of the sunlight that falls on it. This reflection makes Enceladus one of the brightest objects in the solar system.

Enceladus was discovered by William Herschel in 1789 and visited by the Voyager 1 probe in 1980. As Voyager 2 passed Enceladus in 1981, it revealed that despite the moon's small size, a wide range of terrains were present on the surface. Areas range from old, heavily cratered surfaces to young tectonic deformed terrain, with some regions of the surface as young as 100 million years old.

Orbit

Enceladus orbits 238,040 km (147,911 miles) above the center of Saturn. It takes Enceladus 33 hours to orbit Saturn once and also to rotate once. Since Enceladus' rotation and orbit are in sync, one side always faces toward Saturn. Enceladus orbits in the densest part of one of Saturn's outer rings.

Due to the size of Enceladus, scientists believe that the moon was influential in the formation of Saturn's rings. It is possible that the gravity of Enceladus continually ripped apart any rock conglomerations nearby it. This is the same way Jupiter stopped the asteroid belt from forming into a planet.

Surface

As Voyager flew by, scientists observed different types of terrains covering the surface of Enceladus. In the northern hemisphere, cratered terrain covers the surface, indicating an old, unaltered surface. Below the equator, Voyager observed a flat terrain lacking craters. The absence of asteroid impact craters implies a younger surface.

Asteroid impacts take time to occur, if there is an area with a lot of craters, this means they have accumulated over a lot of time. On the other hand, a volcanic eruption can cover impact craters with a new surface. If there are not many impact craters seen, it means the surface has not been there long enough to accumulate impacts and therefore is relatively new.

Due to the absences of craters in the south, scientists speculate that the formation of these flat areas may take only a few hundred million years to recover the surface with new material. In the image below you can see the difference in surfaces.

The northern hemisphere is littered with craters, while the south is relatively flat.
enceladus

Recent Cassini observations show that tectonic activity is renewing the landscape on Enceladus. One of the blue areas in the southern polar region was observed at very high resolution during a flyover by the Cassini Satellite. It sent back images of areas with extreme tectonic deformation and boulder-covered terrain. In the southern hemisphere, cracks appear on the surface. These canyons extend 200 kilometers long, 5-10 km and up to 1 km deep.

Atmosphere

There is no atmospheric rain on Enceladus, but water vapor emitted from geysers on the surface. The source of the atmosphere may be volcanism, geysers, or gasses escaping from the surface or the interior.The atmosphere of Enceladus is composed of 91% water vapor, 4% nitrogen, 3.2% carbon dioxide, and 1.7% methane. Water vapor is emitted from ice volcanoes through a process called cryovolcanism. Some scientists think that the satellite's surface is covered with a layer of fluid ice, while others argue that it is a form of solid ice and rock cold objects.

Summary

Enceladus is one of the largest of Saturn's 62 moons. It is one of the brightest objects in our solar system because its surface is covered in reflective ice. Satellite passes of Enceladus show the surface in the southern hemisphere is being renewed by what is believed to be cryvolcanism.

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