了解宇宙是如何运行的（2010）

How the Universe Works S11E02

Part 3 April 10, 2023, 10:20 a.m.

what temperature liquids boil.
在地球的海平面上
Here on Earth
at sea level,
在地球的海平面上
Here on Earth
at sea level,
水的沸点大约是华氏212度（100摄氏度）
the boiling point of water
is about 212 degrees Fahrenheit,
但是在丹佛附近的山上
but up here in the mountains
near Denver,
这里的海拔比较高
we're at a higher altitude.
压在我们身上的大气压比较少
We've got a lot less
atmosphere pressing down on us,
所以它在一个较低的温度下沸腾
and so it boils
at a lower temperature.
我们在这里放一个温度计
Let's put
a thermometer in here.
这里是200华氏度（约93摄氏度）
There's 200 even right there.
这比海平面的沸腾温度低得多
That's a lot cooler boiling
temperature than at sea level.
现在，如果你到更高的高度，在地球上的10万英尺高空（30公里）
Now, if you go to even higher
altitudes at 100,000 feet
地球上这里的气压
here on the Earth,
the air pressure is about
地球上这里的气压
here on the Earth,
the air pressure is about
就和火星表面差不多了
what it is
on the surface of Mars.
在火星表面
On the surface of Mars,
水在环境温度下就会有效地沸腾了
water will boil effectively
at ambient temperature.
我们根本不需要加热它
We wouldn't have
to heat it at all.
你只需把一杯水放在火星表面
You just put a glass of
water on
它就会沸腾并消失
the surface of Mars, and it'll
boil and disappear away.
但这颗行星的表面告诉我们
ROWE: But the planet's surface
tells us that dry Mars
干燥的火星在过去非常不同
was very different in the past.
塞勒:当你看到像河道这样的东西
THALLER: When you see things
like river channels
可能需要数百万年的时间才能雕刻出来
that probably took millions
of years to carve,
这让我们知道，火星的大气曾经
that gives you an idea that
the atmosphere was once very,
非常非常不一样
very different.
非常非常不一样
very different.
它必须很厚
It had to be thick to allow
才能让液态水存在于表面
liquid water to exist on
the surface.
为了调查火星曾经厚厚的大气层
ROWE: To investigate
what happened to that thick
发生了什么
Martian atmosphere,
MAVEN开始行动
MAVEN swings into action.
塞勒:MAVEN任务的主要目标之一是
THALLER:
One of the main objectives of
测量火星上的氩气
the MAVEN mission was to
measure argon on Mars.
氩的种类略有不同
There are slightly different
kinds of argon.
我们称之为同位素
We call these isotopes,
基本上，这意味着原子核里
and basically,
it means that there's just
多了一个中子
an extra neutron in the nucleus.
所以有一种类型的氩
So there's one type of argon
that's just a little bit
只比另一种类型重一点
So there's one type of argon
that's just a little bit
只是重了一个中子
heavier than the other type
just by one neutron,
没重多少
not by much.
在大气层的高处
ROWE:
High up in the atmosphere,
MAVEN将“好奇号♥”标记为地面上的团队
MAVEN tag teams with Curiosity
down on the surface.
他们测量了轻氩和重氩的含量
They measure the amount of
light and heavy argon.
塞勒:氩有什么特别之处？
THALLER: Now, what's special
about argon?
氩的活性不强
Well, argon
is not very reactive,
不会参与很多化学反应
doesn't really get involved in
a lot of chemistry.
它不会被岩石吸收，变化不大
It's not really absorbed by
rocks, doesn't change much.
一旦它被释放出来，它就会在周围徘徊
Once it's emitted,
it kind of hangs around.
这使得它非常有价值，因为这意味着
And that makes it very
valuable, because it means it
它在星球的历史中一直保持着
stays in pretty much
its pristine, pure form
原始、纯净的形态
through the history
of the planet.
当地球上的研究人员比较了
ROWE: When the researchers
back on Earth
两个火星机器人的读数时
compare the readings from
the two Martian robots,
发现有些地方不太对
something doesn't add up.
萨特:在火星表面
SUTTER: With Curiosity
“好奇号♥”让我们看到了重氩和轻氩的
on the surface, we see
a certain ratio of heavy
一定比例
to light argon.
我们期望同样的比例存在于大气层中
And we expect that same ratio to
exist up in the atmosphere,
但在MAVEN中，我们看到了不同的比例
but with MAVEN,
we see a different ratio.
我们看到的轻氩
We see far less
of the light argon
比我们在地表看到的
We see far less
of the light argon
要少得多
than we do down
on the surface.
所以这个比例被打乱了
So something is
messing with that ratio.
我们能想到的唯一能扰乱氩气比例的东西
The only thing we can think of
that can mess with
就是来自太阳的太阳风
the ratio of argon is
the solar wind from the sun.
太阳不断喷射出的粒子流
ROWE:
The sun spits out a constant
被称为太阳风
stream of particles
called the solar wind.
太阳风超过100万华氏度（约38万摄氏度）
The wind is over a million
degrees Fahrenheit
速度高达每秒500英里
and travels at up to
500 miles a second.
速度高达每秒500英里
and travels at up to
500 miles a second.
当它到达火星时
When it reaches Mars,
it strips away
它会带走大气层高处的气体
gases high up in
the atmosphere.
氩越轻
The lighter the argon is,
进入大气层的位置就越高
the higher it gets up into
the atmosphere.
这意味着它会
That means that
that gets blown
优先被太阳风吹走
away preferentially
by the solar wind.
较重的氩离子会留在较低的位置
The heavier argon stays
a little bit
受到更好的保护
lower down and a little bit
more protected.
所以当你观察大气中
So when you look at the ratio
in the atmosphere of the light
轻氩和重氩的比例时
argon to the heavy argon,
就能知道随着时间的推移流失了多少
it gives you an idea of how
much has been lost over time.
MAVEN的数据显示
ROWE: MAVEN's data
reveals that Mars
火星已经失去了大气中65%的氩气
has lost 65 percent
of the argon
但太阳风仍然继续轰击着
from its atmosphere,
and the solar wind continues to
这颗行星
bombard the planet.
火星的大气层正被太阳辐射
The atmosphere of Mars is
being stripped away by
以每秒四分之一磅的速度剥离
solar radiation by a quarter
of a pound every second.
这种大气损失的速度导致了一个结论
ROWE: This rate of atmospheric
loss leads to one conclusion.
太阳风夺走了火星曾经
The solar wind
robbed Mars of its once
浓厚的大气层，也带走了火星上的水
thick atmosphere, and with it,
the planet's water.
浓厚的大气层，也带走了火星上的水
thick atmosphere, and with it,
the planet's water.
但还有一个问题