了解宇宙是如何运行的（2010）

How the Universe Works S06E08

Part 2 Dec. 22, 2021, 7:23 p.m.

and cool to very,
very chilly temperatures.
那么，水冰能否在水星背对太阳的那一面
So could water ice
survive on the side of Mercury
存活下来呢？
facing away from the Sun?
夜间是非常寒冷的
The nighttime side is
very bitterly cold.
如果这是故事的结尾
If that were the end
of the story,
那么可能会有
you might be able to have,
你懂的，在水星背对太阳的那一面
you know, frozen water,
icy water, on the side
存在有结冰的水
of Mercury facing away
from the Sun.
但水星并不是一边一直朝着太阳
But Mercury doesn't keep one
side always locked to the Sun
另一边一直背对着太阳
and one side always facing away.
它实际上是旋转的
It actually does rotate.
它每绕太阳转两圈
It rotates three times
for every two trips
就自转三圈
it takes around the Sun.
当水星旋转时
As Mercury turns,
太阳会蒸发所有面对它的水冰
the Sun would vaporize
any water ice facing it.
但是否有太阳无法到达的
But are there secret
hiding places
秘密藏身之处呢？
where the Sun cannot reach?
为了找到答案，行星科学家尼娜·兰扎
To find the answer,
planetary scientist Nina Lanza
在冰岛的裂缝中搜寻
searches fissures in Iceland.
所以我们可以看到，在表面上，没有冰存在
So here we can see,
at the surface, there's no ice.
这里太暖和了，但如果我们往下看这个裂缝
It's too warm, but if we look
down in this fissure here,
只有大约20英尺深
it's only about 20 feet deep,
但在底部，确实有一些冰
but at the bottom,
there's actually some ice.
所以如果我们测量一块在太阳下晒过的岩石
So if we measure a rock
that's been in the Sun,
比如这一块，我们可以看到它实际上非常温暖
let's say this one, we can see
it's actually pretty warm.
温度大约是61华氏度
It's about 61 degrees
Fahrenheit,
但如果我们瞄准这个凹洞的底部
but if we aim, now, for the
bottom of this hollow,
现在我们可以看到，温度大约是33华氏度……不
we can see now,
it's about 33... nope.
它是下降温度是32华氏度
It's dropping.
It's 32 degrees Fahrenheit,
这是因为太阳并没有到达
and this is because
the Sun doesn't really
这个地方的底部，这是关键
get to the bottom of this place,
and that's the key.
虽然这些冰隐藏在裂缝中
While this ice
is hidden in a fissure,
但在水星上，这些冰存在于
on Mercury the ice
survives in craters
水星北极的陨石坑中
on the planet's north pole,
永远受不到强光照射
forever safe from the glare
of direct sunlight,
因为这些陨石坑位于完美的位置
because these craters
sit in a perfect spot.
与太阳相比，水星的轴线倾斜不大
Mercury's axis doesn't tilt
very much compared to the Sun.
地轴大约倾斜23度
The Earth's axis tilts
about 23 degrees,
但水星几乎是垂直的
but Mercury is pretty much
straight up and down,
这意味着无论天空中的太阳有多大
and that means that as large
as the Sun is in the sky,
两极都有阳光永远无法到达的陨石坑
there are craters on the poles
that sunlight never gets to.
他们总是冷的
They're always cold.
所以水星的表面
So the surface of
Mercury is heated
在绕太阳运动的过程中被加热，然后冷却
and then cooled
as it moves around the Sun,
但有一些陨石坑，总是黑暗和寒冷的
but there are craters that are
always dark and always cold.
尽管困难重重，尽管一切都表明
Against all the odds,
despite everything that suggests
这种情况不应该发生
this shouldn't happen,
但水星的确是这种水冰的避风港
Mercury is a safe haven
for this water ice.
这些陨石坑的底部被称为冷阱
The bottoms of these craters
are called cold traps
因为它们太冷了，以至于
because they're so cold
that any water
任何到达那里的水基本上永远停留在那里
that gets there stays
there basically forever.
它可以持续几十亿年
It can last literally
for billions of years.
但它是从哪里来的呢？
But where would it
have come from?
它可能来自彗星和小行星
It probably came from
comets and asteroids.
彗星是巨大的冰块
Comets are giant chunks of ice.
所以如果一颗彗星撞击水星
So if a comet hits Mercury,
就会产生大量的冰
that's going to deliver
a lot of ice,
事实上，我们知道
and, in fact, we know
a lot of asteroids
很多小行星上也有冰
have ice on them as well.
所以这两个东西都可以把水送到水星
So both of these things
could deliver water to Mercury.
彗星和小行星将水冰
Comets and asteroids
brought water ice
带到太阳系最内层的行星
to the innermost planets
of the solar system.
同样的水输送系统
This same water delivery system
也为地球提供了生命所需的元素
gave Earth the elements
needed for life.
尽管水星上有少量的冷冻水
And though Mercury has
pockets of frozen water,
但它永远无法利用这些水来培养生物
the planet can never use it
to develop living organisms.
水星向我们真正展示的是
What Mercury is really
showing us is that you can start
可以从行星的基本构造块开始，对吗？
with the same basic building
blocks for planets, right?
可以有本质上相同的材料
You can have essentially
the same materials,
但最终得到非常不同的环境
but end up with very
different environments.
与其他行星♥相♥比
Compared to the other planets,
水星最终成为一堆行星中最弱小的一颗
Mercury ended up as
the runt of the litter.
但有证据表明，情况并非总是如此
But there's evidence
this wasn't always the case.
这个小小的世界曾经会比现在大得多吗？
Could this little world have
once been much, much bigger?
我们有关于如何在太阳系中
We have theories for
how the planets first formed
形成行星的理论
in our solar system,
但水星并不适用
but Mercury just doesn't fit in.
当你观察组成我们太阳系的
When you look at
the family of planets
行星家族时，你懂的
that make up our solar system,
you know,
水星看起来确实有点奇怪
Mercury does seem to be
a little bit of a weirdo.
在地球上，我们的地核相对较小
On Earth, we have
a relatively small core
地幔较厚，地壳较薄
and a thick mantle
and a thin crust.
所以你把地核和地球的大小相比
So you compare the core of the
Earth to the size of the Earth,
它真的很小
it's relatively small.
如果你看水星，它完全不是那样的
If you look at Mercury,
it's not that way at all.
地核与行星本身相比绝对是巨大的
The core is absolutely huge
compared to the planet itself.
1974年，水手10号♥成为第一艘飞越水星的航♥天♥器
而这次任务，使它发现了一些完全出乎意料的事情
磁场
火星从来没有存在过的磁场
金星也没有磁场
所以水星有磁场是一个惊喜
至于地球，在地球内部深处有一个对流运动的金属流体核心
是它产生了全球磁场
它表面的磁场强度是水星的一百倍
如何产生磁场？水星是冷的，所以必须要大
你可能会认为，对于一颗行星来说，水星的尺寸无法维持磁场
但由于水星的核心非常大和密集，在中心可能仍然是熔融的
所以它可以维持磁场
水星巨大的铁核被异常薄的
Mercury's huge
iron core is surrounded
岩石层包裹着
by an unusually
thin mantle of rock.
它只是看起来很奇怪
It just looks odd.
这很有趣
It's funny.