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Oceans on Saturn's Moon Enceladus!

直径500公里 土卫二只是土星62个卫星中第六大的
At 500 kilometers in diameter, Enceladus is only the sixth largest of Saturn’s 62 moons.
但是这里是SciShow Space它开始占据我们心中不可思议的绝大部分
But here at SciShow Space, it’s starting to occupy an increasingly large part of our
hearts. That is because it has been confirmed that it contains a huge subsurface ocean,
making it one of the solar system’s most promising candidates for extra-terrestrial
而你怎么能不爱它呢 我是Hank Green 欢迎来到 SciShow Space News
life, and how could you not love that? I’m Hank Green and welcome to SciShow Space News.
上一周 在科学杂志 来自NASA和加利福利亚理工学院的天文学家宣布
Last week in the journal Science, astronomers from NASA and Caltech published evidence that
小小的土卫二有巨大的地下 或者说冰下海洋
little Enceladus has a giant underground, or rather under-ice, ocean. This new evidence
这个新的发现增强了 自2005年 NASA的卡西尼号宇宙飞船第一次观测到
reinforces what astronomers have been theorising since 2005 when NASA’s Cassini spacecraft
first observed giant geyser-like plumes of water erupting near Enceladus’s south pole.
They thought pressure changes due to the moon’s irregular orbit might be forcing water from
an underground ocean up through cracks in its icy surface, but they weren’t sure because
但是他们不确定 因为没有证据证明有热能使海洋保持液态
there was no evidence for a source of heat that would keep the ocean liquid, and there
could’ve been other explanations for those plumes.
自此卡西尼号飞过了土卫二19次 有3次飞近天体探测 向地球送回了
Since then, Cassini has flown by Enceladus 19 times in three flybys and sent particularly
尤其清晰的无线电讯号 这些信号指明了一些对土卫二的重力的困扰
clear radio signals back to Earth. These signals indicated something confusing about Enceladus’s
gravity. A region near the south pole of the moon turned out to have a stronger gravitational
这种异常现象经常是由于巨大的东西 例如
field than it should have. Such abnormalities can usually be explained by large masses like
或者地壳组成的差异 在这个地区实际上有一个巨大的洼地
mountains or by differences in crust composition, but this region actually has a giant depression
而土卫二的地壳只是冰冻的水 但冰下的致密地区
in it, and Enceladus’s crust is just frozen water. But a dense region under the ice would
可能导致这个异常 而什么比冰更密呢 液态水 确切的说比冰密7%
account for this anomaly, and what’s denser than ice? Liquid water, 7% denser than ice
to be exact. So scientists think this change in gravitation is caused by a hidden ocean
太约同等于苏必略湖的体积 据同样复杂的数学
with about the same volume as Lake Superior. According to some complicated math, they estimate
他们估计这个海洋约有十公里深 坐落于冰壳之下
that the ocean is about ten kilometers deep sitting beneath an ice shell that’s about
大约30到40公里深的地方 这也解释了土卫二南极周围的洼地
30 to 40 kilometers thick. This would also explain the depression around Enceladus’s
如果冰壳融化到水里 它会减少这个体积 让它凹进去
south pole. If the ice crust melted into water, it would reduce its volume, making a dent.
So all the evidence points to an underground ocean and therefore the possibility of habitability
因为不仅是有生命可以存活的液态水 地下还有岩石
because not only is there liquid water, which life is really into, but there’s rock underneath
在土卫二的地心 液态水与岩石河床互相作用意味着化学反应
it in Enceladus’s core. Liquid water interacting with a rocky bed means chemical reactions
可以产生营养素 而所有那些缺少的是能量源
that could produce nutrients. All that’s missing is an energy source. And if Enceladus
而如果土卫二地质构造活跃的话 上个星期的发现也证明了拥有地核地幔和
is tectonically active, as last week’s findings also suggest, with a core, mantle and crust
岩石 水 冰都在移动互相摩擦的地壳
of rock, water and, ice all moving around creating friction with one another, that could
在那里提供了能量源 地球这里的极端微生物 像古生菌 通过地热能促使的反应
be an energy source right there. Extremophiles here on Earth, like archaea, use reactions
很棒地过活着 谢谢你
driven by geothermal energy to get by very nicely; thank you.
所以作为生命的候选者 土卫二很可能更有保障
So as a candidate for life, Enceladus is looking pretty promising competing with the likes
相比于其他我们最喜欢的 木卫二 木星的卫星 那里天文学家也预言了
of another of our favourites, Europa, a moon of Jupiter which astronomers also predict
有地下液体海洋 也观测到释放了羽状水柱
has a liquid subsurface ocean and which has also been observed releasing plumes of water.
NASA is putting together preliminary plans for a robotic probe to Europa, but with Enceladus
但既然土卫二加入了海洋俱乐部 他们必须得决定往哪儿投钱了 更何况
joining the ocean club, they’re gonna have to decide where to put their money. Move over,
感谢观看SciShow Space News 尤其是我们超级聪明的Subbable订阅者
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