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| Sunday, 27 March 2005 |
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Junior Observer |
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Editorial
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Scientists believe that these new results from Cassini may be the first evidence of gases originating either from the surface or possibly from the interior of Enceladus.
In 1981, NASA's Voyager spacecraft flew by Enceladus at a distance of 56,000 miles (90,000 km) without detecting an atmosphere. Its possible detection may have been beyond Voyager's capabilities, or something may have changed since then.
This is the first time since Cassini arrived in orbit around Saturn last summer, that an atmosphere has been detected around a moon of the planet, other than its largest moon, Titan. Enceladus is a relatively small moon. The gravity it exerts is not enough to hold an atmosphere for long. Therefore, a strong continuous source is required to maintain the atmosphere at Enceladus.
The need for such a strong source leads scientists to consider eruptions, such as volcanoes and geysers. If such eruptions are present, Enceladus would join two other such active moons, Io of Jupiter and Triton of Neptune. Since the Voyager flyby, scientists have suspected that this moon is geologically active and is the source of Saturn's icy E ring. Enceladus is the most reflective object in the solar system, reflecting about 90 per cent of the sunlight that hits it. If Enceladus does have ice volcanoes, the high reflectivity of the moon's surface might result from continuous deposition of icy particles originating from the volcanoes.
Enceladus' diameter is about 310 miles (500 km), which means it would fit in the state of Arizona. Despite its small size, Enceladus exhibits one of the most interesting surfaces of all the icy satellites.
(Courtesy - NASA)
A glossary of space terms
If you are someone who is fascinated by the numerous mystic happenings of space, but are stumped by the various space science terms used in books and documentations on this topic, then we will help you reach for the stars by explaining these terms. Some are simple and some are complicated, but we will help enhance your knowledge through these pages as and when space is available.
Crater
A bowl-shaped depression caused by a comet or meteorite colliding with the surface of a planet, moon, or asteroid. On geologically active moons and planets (like Earth), craters can result from volcanic activity too.
Atmosphere
The layer of gases surrounding the surface of a planet, moon, or star.
Erosion
Natural processes that wear or grind away the surface of an object. On Earth, the major agents of erosion are water and wind.
Aurora
A phenomenon produced when the solar wind (made up of energized electrons and protons) disturbs the atoms and molecules in a planet's upper atmosphere.
Some of the energy produced by these disturbances is converted into colourful visible light, which shimmers and dances. Auroras have been seen on several planets in our solar system.
On Earth, auroras are also known as the "Northern Lights" (aurora borealis) or "Southern Lights" (aurora australis), depending on in which polar region they appear.
Lunar scars
The surface of the Moon is scarred by craters up to 250 km (160 miles) in
diameters. These are the results of meteorites smashing into the surface
long ago. It is believed that some volcanic activity also has taken place
even on the Moon, for dark lava flows cover the lowland areas of the Moon.
The surface of the Moon is incredibly ancient. Would you believe that the
youngest rocks brought back by the Apollo astronauts are more than 3,000
million years old?
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