Enceladus is the eighth of Saturn's known satellites:
orbit: 238,020 km from Saturn
diameter: 498 km
mass: 7.30e19 kg
In Greek mythology Enceladus was a Titan who was defeated in battle and buried under Mount Etna by Athena.
Discovered in 1789 by Herschel.
Craters and smooth plains Enceladus has the highest albedo (>0.9) of any body in the solar system. Its surface is dominated by fresh, clean ice.
At least five different types of terrain have been identified on Enceladus. In addition to craters there are smooth plains and extensive linear cracks and ridges. At least some of the surface is relatively young, probably less than 100 million years.
This means that Enceladus must have been active until very recently (and perhaps is still active today). Perhaps some sort of "water volcanism" is at work.
Enceladus is much too small to be heated by the decay of radioactive material in its interior at present (the heat would have all dissipated long ago).
Cassini closeup view (looks like Europa?) Enceladus is locked in a 1:2 resonance with Dione (similar to the situation between Io and Europa). This may provide a heating mechanism but it is probably insufficient to melt water ice. Enceladus may therefore be composed of some low-melting point material rather than pure water.
Enceladus may be the source of the material in Saturn's tenuous E ring. And since the material cannot persist in the ring for more than a few thousand years, it may be due to very recent activity on Enceladus. Another possibility, though, is that the rings are maintained by high-velocity collisions between dust particles and the various moons.
Enceladus 是土星已知衛(wèi)星中距其第八遠的一顆：
公轉(zhuǎn)軌道：距土星 238,020 千米
衛(wèi)星直徑：498 千米
質(zhì)量：7.30e19 千克
在希臘神話中，Enceladus是一個巨人，他在戰(zhàn)斗中戰(zhàn)敗后被雅典娜埋葬在Etna山下。
它由赫歇耳于1789年發(fā)現(xiàn)。
土衛(wèi)二在太陽系諸多星體中具有較高的反照率 (>0.9)。它的表面有新鮮、干凈的空氣。
土衛(wèi)二表面至少有五種地形已被確認。除了隕石坑外還有平緩的平原和沿直線延伸的裂縫與山脊。一些表面相對來說較年輕，可能小于1億年。
這意味著土衛(wèi)二最近可能非常活躍（可能至今都很活躍）。也可能有一些“水火山”依然動作。
土衛(wèi)二太小，不能被內(nèi)部衰退的放射性物質(zhì)加熱（熱量可能在很久以前既已衰退完）。
土衛(wèi)二與土衛(wèi)四以1:2的固定共動關系運行（與木衛(wèi)一和木衛(wèi)二的情形相似）。這形成了供熱機制，但這還不足以溶解冰。土衛(wèi)二可能由一些低溶點的物質(zhì)，如純水組成。
土衛(wèi)二可能是土星的稀薄的E光環(huán)中物質(zhì)的供給源。另外由于這物質(zhì)不可能在光環(huán)中存在數(shù)千年之久，它可能與土衛(wèi)二最近的活躍有關。另外光環(huán)也有可能是由高速的不斷碰撞的粒子與不同的衛(wèi)星共同維系。
orbit: 238,020 km from Saturn
diameter: 498 km
mass: 7.30e19 kg
In Greek mythology Enceladus was a Titan who was defeated in battle and buried under Mount Etna by Athena.
Discovered in 1789 by Herschel.
Craters and smooth plains Enceladus has the highest albedo (>0.9) of any body in the solar system. Its surface is dominated by fresh, clean ice.
At least five different types of terrain have been identified on Enceladus. In addition to craters there are smooth plains and extensive linear cracks and ridges. At least some of the surface is relatively young, probably less than 100 million years.
This means that Enceladus must have been active until very recently (and perhaps is still active today). Perhaps some sort of "water volcanism" is at work.
Enceladus is much too small to be heated by the decay of radioactive material in its interior at present (the heat would have all dissipated long ago).
Cassini closeup view (looks like Europa?) Enceladus is locked in a 1:2 resonance with Dione (similar to the situation between Io and Europa). This may provide a heating mechanism but it is probably insufficient to melt water ice. Enceladus may therefore be composed of some low-melting point material rather than pure water.
Enceladus may be the source of the material in Saturn's tenuous E ring. And since the material cannot persist in the ring for more than a few thousand years, it may be due to very recent activity on Enceladus. Another possibility, though, is that the rings are maintained by high-velocity collisions between dust particles and the various moons.
Enceladus 是土星已知衛(wèi)星中距其第八遠的一顆：
公轉(zhuǎn)軌道：距土星 238,020 千米
衛(wèi)星直徑：498 千米
質(zhì)量：7.30e19 千克
在希臘神話中，Enceladus是一個巨人，他在戰(zhàn)斗中戰(zhàn)敗后被雅典娜埋葬在Etna山下。
它由赫歇耳于1789年發(fā)現(xiàn)。
土衛(wèi)二在太陽系諸多星體中具有較高的反照率 (>0.9)。它的表面有新鮮、干凈的空氣。
土衛(wèi)二表面至少有五種地形已被確認。除了隕石坑外還有平緩的平原和沿直線延伸的裂縫與山脊。一些表面相對來說較年輕，可能小于1億年。
這意味著土衛(wèi)二最近可能非常活躍（可能至今都很活躍）。也可能有一些“水火山”依然動作。
土衛(wèi)二太小，不能被內(nèi)部衰退的放射性物質(zhì)加熱（熱量可能在很久以前既已衰退完）。
土衛(wèi)二與土衛(wèi)四以1:2的固定共動關系運行（與木衛(wèi)一和木衛(wèi)二的情形相似）。這形成了供熱機制，但這還不足以溶解冰。土衛(wèi)二可能由一些低溶點的物質(zhì)，如純水組成。
土衛(wèi)二可能是土星的稀薄的E光環(huán)中物質(zhì)的供給源。另外由于這物質(zhì)不可能在光環(huán)中存在數(shù)千年之久，它可能與土衛(wèi)二最近的活躍有關。另外光環(huán)也有可能是由高速的不斷碰撞的粒子與不同的衛(wèi)星共同維系。