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If they found even a few martian microbes,
如果他们找到哪怕只是几种火星微生物
in my opinion,
在我看来
it would be one of the most exciting discoveries ever made.
这将成为有史以来最令人振奋的发现之一
But even if mars is barren,
但是即便火星没有生命
there are other places to look for liquid water.
仍可以在其它星球寻找液态水
One of them lies a mere 30 million miles from Mars.
其中一处距离火星仅有3万千英里远
On a small, mysterious moon that orbits the giant planet Jupiter.
就在大行星木星的一个小而神秘的卫星上
This is Europa.
这就是木卫二
Europa is tiny -- just under 2,000 miles in diameter
木卫二非常小，直径不到2千英里
and it's very cold -- minus 260 degrees.
而且非常冷，仅有零下260度
The entire moon is covered in a layer of ice perhaps 15 miles thick.
整个卫星被大约15英里厚的冰层覆盖着
But Europa may have a hidden heat source beneath the surface.
但是木卫二地表以下可能隐藏着一个热源
Europa orbits Jupiter once every 3.6 days,
木卫二每3.6天就围绕木星转一圈
in an egg-shaped path.
其轨道呈鸡蛋形状
The gravitational pull from Jupiter changes constantly,
木星对其的引力不断变化
stretching, then compressing europa.
不断拉伸然后挤压木卫二
This process is like kneading a piece of clay
这过程就像揉捏一块粘土
to make it warm and soft,
使其变得又热又暖
and the heat produced may be enough to melt the underside of the ice sheet.
所产生的热量也许足够融化冰层的底层
creating a hidden ocean of liquid water protected
从而产生一个隐蔽的液态水的海洋
from the vacuum of space by the solid ice above.
由上面覆盖着厚厚的冰层保护着与真空隔绝
If so, there could be aliens living here --
若真如此，那里可能有生命存在
creatures that have evolved to exploit this dark and ancient water world.
进化得足以适应这种黑暗和古老的水世界
I think it's even reasonable to guess at some of their physical features.
我认为甚至可能想象得出它们的体征
Aliens here would probably swim in a similar way to our own ocean life,
那里的生命可能和我们的海洋生物一样游泳
since liquid water is the same stuff everywhere.
因为液态水在哪里都是一样的
