了解宇宙是如何运行的（2010）

How the Universe Works S06E02

Part 2 Dec. 22, 2021, 7:22 p.m.

我尝了尝，没错，是咸的
and yeah, sure enough, it's salty.
莫诺湖的这些盐
The salt at lake mono
是在水蒸发时结晶形成的
crystallizes as the water evaporates,
这是它形成的唯一方式
the only way it can form.
研究人员相信
The researchers believe the same process
谷神星上也发生了同样的过程
is taking place on Ceres.
这意味着地表下一定有液态水
This means there must be liquid water beneath the surface...
但怎么可能？这是在小行星带，这里是深度冰冻的世界
...but how, out in the deep freeze of the asteroid belt?
这些亮点位于陨石坑的中心
These bright spots are located in the centers of craters.
它们位于表面的裂缝周围
They're located around cracks in the surface,
这告诉我们
and that is telling us that this material
这种物质是从下面涌到表面上来的
is coming from under the surface and welling up onto it.
绝对没有人预料到
Absolutely nobody expected there to be liquid water
谷神星表面下方会有液态水
beneath the surface of Ceres.
我们无法解释能让这些水保持的温度
We cannot explain what is keeping that water warm.
在一些卫星上
On some moons,
引力的牵引会使内部保持温暖
gravitational tugging keeps the interiors warm,
但谷神星并没有真正靠近任何其他非常大的天体
but Ceres is not really near anything else that's very large.
所以令人惊奇的是
So the amazing thing is that we may not even understand
我们甚至不知道这颗岩石行星是如何工作的
how rocky planets work.
可能还有另一种能源
There may be another source of energy,
另一种加热内部的机制
another mechanism for heating the interior
只是我们还没有发现
that we haven't even discovered yet.
为了找出谷神星是如何有液态水的
To find out how Ceres has liquid water,
我们必须把时钟倒带回46亿年前
we have to rewind the clock 4.6 billion years.
太阳形成过程中留下的碎片
Debris left over from the formation of the Sun
撞击在一起形成矮行星
slams together to form the dwarf planets.
当它们成形时，较重的岩石材料下沉到中心
As they take shape, the heavier, rocky material
形成一个炽热的熔化的核心
sinks to the center and forms a hot, molten core.
泥水和浮冰漂浮到顶部
Slushy water-ice floats to the top.
一段时间内，它保持液态
For a while, it stays liquid, but once the core cools,
但一旦核心冷却，它就会冻结并形成固体的外壳
it freezes and forms the solid mantel and crust.
这个表面应该仍然是固体的
That surface should still be solid,
所以盐斑的出现仍然是一个令人困惑的谜
so the salt patches remain a perplexing mystery.
我们仍然没有回答这个问题
We still haven't answered the question,
“谷神星上怎么可能还有液态水？”
"how could there actually still be liquid water on Ceres?"
这仍然是一个很难回答的问题
That's still a hard question to answer.
一种可能发生的方法是
One way this could happen is if it's not actually pure water,
可能它不是纯水，而是和其他东西的混合物
if you've mixed it with something else.
一些科学家提出
Some scientists have proposed
地表之下可能存在咸海
that a salty ocean lies beneath the surface.
高浓度的盐降低了水的冰点
The high concentration of salt
使水保持液态
lowers the freezing point of the water, keeping it liquid.
当小行星撞击使地壳破裂时
When asteroid impacts fracture the crust,
咸水从下面渗出
this salty water oozes up from below.
液体迅速蒸发，但盐仍然存在
The liquid swiftly evaporates, but the salt remains,
并在表面留下一个明亮的白点
leaving a brilliant white spot on the surface.
事实上，我敢打赌
In fact, I'm willing to bet
现在可能就会有水冒出来
there could be water coming up now,
把盐带到表面
bringing salts up to the surface,
然后蒸发到太空中
evaporating away into space,
这意味着液态水
and that means liquid water is very close
现在非常接近谷神星的地表面
to the surface of Ceres right now.
谷神星的袖子里有一张更令人吃惊的卡片
Ceres has an even more startling card up its sleeve.
最近的研究表明谷神星是一个“移♥民♥”
Recent research suggests that it's an immigrant.
它不是在小行星带附近形成
It didn't form anywhere near the asteroid belt.
谷神星很有可能
Ceres may have been born
是与数百颗其他矮行星一起诞生
alongside hundreds of other dwarf planets,
它们距离太阳有数十亿英里远
many billions of miles away from the Sun.
那它是怎么来到这里的？
So how did it get here?
我们发现的大多数矮行星
Most of the dwarf planets we've discovered
都位于海王星轨道以外的太阳系中
lie far out in the solar system beyond the orbit of Neptune,
但是谷神星所在的小行星带
but Ceres orbits between Mars and Jupiter
是在火星和木星之间的轨道上
in the asteroid belt.
但谷神星的位置
But its location isn't the only hint
并不是证明它可能是闯入者的唯一证据
Ceres might be an interloper.
正常情况下天体的材料
Normally, celestial objects are made of the same materials
与周围其他天体的材料应该相同
as the other bodies in their neighborhoods,
但谷神星的情况并非如此
but that's not the case with Ceres.
小行星带主要由干燥的岩石体组成
The asteroid belt is mostly made up of dry, rocky bodies
都含有构成岩石内行星的
composed of the same heavy elements
那些重元素组成
that form the rocky inner planets.
谷神星却截然不同
Ceres is very different.
谷神星本质上是一个冰块的世界，对吧？
Ceres is essentially an icy world, right?
它是用冰块而不是石头做的
It's made out ices instead of rocks,
考虑到它在那个位置，这就有点奇怪
and so that's kind of weird, considering where it is.
谷神星上的冰还含有一些化合物
The ice on Ceres also contains chemical compounds
但这些化合物
that in the early years of the solar system,
并不存在于太阳系早期的小行星带中
didn't exist in the asteroid belt.
我们对谷神星了解得越多
The more we learned about Ceres,
它就越神秘
the more mysterious it became.
其中一个问题是
One of the things is that Ceres has quite a lot
谷神星上有大量的氨
of ammonia on it, and we don't find ammonia
我们在太阳系内部附近找不到氨的存在
anywhere near the inner part of the solar system.
但在外太阳系，我们确实找到了氨
But we do find it in the outer solar system.
我们在冥王星、冥王星的卫星卡戎
We've detected ammonia on Pluto, its moon Charon,
以及冰冻的柯伊伯带上都发现了氨
and out in the frozen Kuiper belt,
并且在那里我们也发现了其他的矮行星
where we find the other dwarf planets.
我们认为
We think that the origin of that ammonia
氨的来源应该是在太阳系中非常寒冷的地方
would've had to be in a very cold part of the solar system,
比我们今天发现谷神星的地方还要冷
colder than where we find Ceres today.
但是，一颗带氨的冰矮星
But how an icy dwarf planet with ammonia
是如何在氨无法形成的地方居住的
came to inhabit a place where ammonia can't form...
这是一个巨大的难题
That's a huge puzzle.
我在高山上，现在这里在下着大雪
但在我的下方几千英尺的地方
天气还是相当暖和的，就像夏天一样
对于我们的太阳系来说，也是类似的
在太阳系刚刚形成的早期
嗯，当然，太阳刚刚点燃，那时太阳系内部非常温暖
在46亿年前太阳刚诞生时，比现在更加炽热
太阳会喷发出各种较轻的元素
如氨和氦等
一直把它们喷发到
我们称之为“雪线”的外♥围♥
这就是为什么岩石行星
就像我们生活在太阳系内部的行星
是由岩石和金属构成的
在太阳系中，那些较轻的分子无法留存在这里
但在雪线之外
嗯，也就是我们今天发现木星的地方
温度就要冷得多
这表明谷神星
This suggests to us that Ceres
可能是在太阳系外♥围♥形成的
perhaps formed in the outer solar system
然后向内迁移到
perhaps formed in the outer solar system
小行星带的现在位置
to its present location in the asteroid belt.
我们过去认为
We used to think
行星的轨道是完全不可变的
that planetary orbits were completely immutable,
它们只是像钟表一样来回运转
that they simply ran like clockwork
它们不会四处移♥动♥
and they didn't move around.
现在我们知道事实并非如此
Now we know that that's not the case.
在行星形成的早期阶段
In the early stages of planet formation,
行星会在环绕着
planets move around through the gaseous disc
年轻太阳的气态圆盘里运行
that encircles the young sun,
很像被洋流推动的木筏
much like rafts that are pushed around by ocean currents.
谷神星的氨表明
Ceres' ammonia suggests that dwarf planets
矮行星和年轻的行星
rafted around on the cosmic ocean
一起在宇宙海洋中漂流
along with the young planets.
谷神星是一把冒烟的枪
Ceres is sort of a smoking gun that solar systems
太阳系比我们知道的更具活力和戏剧性
are much more dynamic, much more dramatic than we know.
越来越多的证据表明
There's mounting evidence
谷神星形成于太阳系的外♥围♥
that Ceres formed farther out in the solar system
是某种东西把这个小世界带了进来
and something brought this little world in.
为什么会这样？
What could possibly have done that?
答案是木星
The answer is the planet Jupiter.
在它最初形成之后
After it first formed,
这颗巨大的行星向太阳螺旋接近
the giant planet migrated in towards the Sun.
它巨大的引力扰乱了太阳系其他天体的轨道
Its massive gravity disrupted the orbits of other bodies
包括谷神星的轨道
in the solar system, including that of Ceres.