宇宙（2007）

The Universe S05E02

Part 5 April 22, 2021, 1:48 p.m.

and recent study that it could be from carbon dioxide.
最新研究表明那可能来自二氧化碳
The dry ice going to a gas,
干冰升华成气体
and then that gas basically doing a gas lubrication
这种气体又起到了润滑作用
of the sand that's flowing down.
从而使沙子流动
And frankly,
坦白说
it's still in the midst of exploratory science right now.
现在仍在科学探索当中
And some of these marks have been shown to be dust flows.
现在有些痕迹已被证明是沙尘流动而成
I hope not all of them.
希望不全是这样
I`d like them to be water.
我希望也有水的作用
From ancient oceans to yesterday's flowing gully,
从古大洋到流动的沟渠
the search for water and life on Mars is an ongoing quest,
对火星上水和生命的探索将持续下去
a quest that like a climber's path along an unfamiliar course
这就像是攀岩者选择了一条陌生的道路
is filled with false starts and unexpected detours.
途中将满布失败与曲折
That's what happens when this photograph
这张在火星赤道附近
taken near the martian equator
拍摄到的照片
reminds a lot of people of this.
让大家想起了这个
Could Mars once have supported life?
火星是否曾存在过生命
Mineral evidence from probes like the Spirit rover is encouraging,
勇气号♥采集的矿物证据令人倍受鼓舞
But it can be radically over interpreted.
但这有可能被人借题发挥
And we have to be careful
我们要小心仔细
not to jump over a line that goes beyond
不要逾越我们现有的
what the current data, the current experiments,
数据实验和假说
the current hypotheses can support.
可支持的范围
But it's hard as human beings not to just jump over that line.
但是很难做到不逾越
In 2008, thousands
2008年许多人
jumped to an incredible conclusion,
得出了一个不可思议的结论
when a picture taken by NASA's Spirit rover
当勇气号♥探测器拍摄的照片
goes viral across the internet.
公布到网上以后
Doesn't this figure look amazingly like
这张照片看起来
pictures supposedly taken of bigfoot?
难道不像大脚怪吗
Is this proof of life on Mars?
这是火星上有生命存在的证据吗
No.
不
it's a two-inch tall rock.
它只是一个两英寸高的岩石
We still do not have definitive evidence
至今我们还缺乏有力证据
for the existence of life on Mars, ever.
证明火星上存在生命一直都没有
Like the 19th century canals
就像19世纪的运河
and the 20th century face
20世纪的脸像一样
the martian bigfoot is a 21st century trick of the light.
火星大脚怪就是21世纪光的把戏
And sometimes people don't know
有时候人们不知道
how to distinguish bebetween the facts and the science fiction.
如何区分事实和科幻小说
If there is or was life on Mars,
如果火星上有或有过生命
it probably evolved very early
很可能只在早期的火星
in the planet's history,
形成过
when Mars still had a a magnetic field
当时火星仍然有磁场
shielding it from harmful space radiation.
可以保护它不受太空辐射的伤害
The evidence that Mars used to
曾经有磁场的证据
have a magnetic field lies in the crustal rocks.
就是火星外壳的岩石
Most of the crustal rocks have
绝大部分岩石凝固的时候
a magnetic field frozen in when they solidify.
磁场也被封存在其中
These magnetic rocks, scattered across the red planet,
这些磁性岩石散布于这个红色星球上
give Mars its own version of Earth's northern lights,,
令火星有了自己的北极光
as discovered in 2008,
就像2008年发现的那样
although it may not register as visible light to human eyes.
尽管这极光并非肉眼可见
On Earth, when charged particles from the sun
在地球上当来自太阳的带电粒子
get trapped in Earth's s field lines,
陷入地球的磁场线
smack into the atmosphere,
冲进大气层
they cause the atmosphere to gain energy
让大气层得到能量
and then emit a glow.
然后发射出一道光
The European spacecraft Mars Express
欧洲的宇宙飞船火星快车
recently detected aurora on Mars.
最近探测到了火星上的极光
And what's s actually happening there
那里到底发生了什么呢
is that there are charged particles
那里也有带电粒子涌向磁场线吗
streaming down magnetic field lines
这些磁场线也是由
being made by remnant magnetization in the crust?
外壳剩余的磁场形成的吗
But how did Mars lose its magnetic field?
但是火星的磁场为何会消失
One theory: A little less than four billion years ago,
有种理论是大约不到40亿年前
as Mars cools,
火星变冷的时候
its molten iron core solidifies and stops turning.
其熔融铁核心凝固了不再转动
The motions within the core weren't sufficient
火星核心的运动
to generate an electric current producing a magnetic field.
不足以产生电流来产生磁场
But there's also a faster, and far more violent hypothesis.
但是还有一种更快的更极端的设想
Another more recent idea that's pretty controversial,
最近的另一种有争议的看法是
is that Mars had one or more fairly large moons
火星有一个或几个像月亮一样的
that were actually capture satellites,
大型的捕获卫星
and those moons tidally heated
那些卫星周期性加热
the interior and kept it molten,
火星的内部并维持其熔化
allowing currents to be generated
令电流产生
and thus producing magnetic field.
并因此产生磁场
Now, if a half a billion years after Mars's formation,
那么如果火星成型后5亿年
those moons crashed into the planet,
那些卫星撞向行星
that could have destroyed the magnetic field.
就会破坏磁场
For most scientists, the pieces of the impact theory don't fit.
大多数科学家认为冲击理论说不通
Could satellites large enough to do such damage
首先卫星能大到足以造成如此严重的破坏吗
lose enough inertial energy to be captured in the first place?
会失去足够的惯性能量而被火星捕获吗
This idea that Mars had moons that crushed into it
关于那些卫星在5亿年中
within a half of a billion of years is pretty unlikely.
撞入火星好像很不可思议
But it's not completely impossible.
但也不是完全不可能的
Questions about Mars' magnetic field
关于火星磁场的问题
and the search for life intersect here
以及对生命的搜寻贯穿了这里
in the martian meteorite ALH 84001
在火星陨石阿兰山84001中
In 1996, some scientists
1996年一些科学家
say it contains fossilized martian microbes.
说那里面有火星细菌化石
More scientists say the objects are non-biological.
更多科学家认为那些是非生命物质
All the time since then,
从那时候起
people have been working on this poor little potato-sized meteorite,
人们一直在研究这小土豆般大的陨石
extracting more and more information,
提取了越来越多的信息
but there's actually some new results being presented.
确实提出了一些新成果
In April 2010,
2010年8月
researchers with new radiometric tools
研究者用新的放射性测量工具
announced the earlier estimates of the meteorite's age
测出早期对于这块陨石年龄的估计
are wrong.
是错误的
It's actually younger by
粗略估计它的年龄
a half billion years than we thought, roughly.
比我们想象的要小5亿年
The older date had placed the rock
旧数据显示这块陨石出现于
at a time when Mars was still solidifying,
火星正在凝固的时期
maybe too early for even microbes,
也许对细菌来说都太早了
the new date places the meteorite
新的数据认为它
at just under 4.1 billion years old.
形成不到41亿年
That, of course, is the time, 1 billion years ago,
当然在10亿年前
when, if you thought Mars was habitable,
如果你认为火星曾适合居住的话
that would be the time you would choose,
就是在那个时候
because we think there was water flowing on the surface,,
因为我们认为那时候火星表面有水流
and it was warmer. And it was a thick atmosphere.
气候更温暖也有一个厚厚的大气层
But how can a meteorite from Mars
但是来自火星的陨星
end up on Earth?
如何来到地球的呢
That was Kristina M., from Dallas, Texas,
来自德克萨斯达拉斯的克里斯汀娜
wanted to "Ask the universe"
想要"问问宇宙"
When she texted us:
她问我们
What makes part of one planet
是什么使得行星的一部分
fly off and land on another?
飞离并落到另一个行星上呢
Great question, Kristina.
好问题克里斯汀娜
We've actually found meteorites here on Earth
我们的确在地球上发现了
that are undeniably from Mars.
确定来自于火星的陨石
There's about 50 of them known.
已知的大约有50块
Well, what we think happens is
我们认为
that asteroids occasionally slam into Mars
小行星偶然撞击了火星
and throw chunks of rock out into space
将大块岩石抛进太空
and Earth's gravity can also pull them in.
地球的重力也可以把它们拉进来
So they land here and we find them.
所以它们掉在这里被我们找到了
And in this way, we can actually study
通过这种方法我们确实可以