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It might feel like it was only yesterday that the world was holding its breath
感觉昨天就像全世界都屏住呼吸了一样，
as the Curiosity rover touched down on Mars in one of the most complicated space landings ever.
因为“好奇号”探测器在火星上着陆了，这是有史以来最复杂的太空着陆之一了。
But in August, the rover celebrated its fifth birthday.
但在8月，探测器庆祝了它的五岁生日。
Our little robot's growing up so fast!
我们的小机器人长得真快！
And for a kindergartener, it's made some really impressive discoveries.
对于一个孩童来说，它有很多惊人的发现。
Curiosity's main mission is to find out if Mars is or ever was habitable.
“好奇号”的主要任务是查明火星过去和现在是否适宜居住。
Because for a planet to support life, all of its systems have to be just right.
因为对于一个维持生命的行星来说，它所有的系统都必须恰如其分。
Among other things, the soil has to contain enough nutrients; the atmosphere has to have the right composition and thickness;
除了其它方面，土壤必须含有足够的养分，大气必须有适当的成分和浓度，
and as far as we know, there needs to be at least some amount of water.
而且据我们所知，火星上至少得有一定数量的水。
Over the last five years, Curiosity has taught us lot about all of those things from its home in Mars' Gale Crater.
在过去五年，“好奇号”从它的家，即火星的盖尔陨石坑(Gale Crater)为我们提供了很多这方面的资料。
For one, it recently confirmed that the crater used to have at least one habitable lake,
举例来说，它刚刚确认这陨石坑过去至少有个宜居湖，
based on sedimentary rocks on Mount Sharp, a mountain in the crater.
证据是陨石坑里夏普山上的沉积岩。
The structure and chemistry of the rocks point to a lakey environment. Which is awesome!
岩石的结构和化学成分都指向它曾是个湖泊。这很棒！
But Curiosity has also been finding the remains of a watery environment for years.
但是“好奇号”这些年来一直在寻找水环境中的残留物。
In 2014, it found the deposits made of mudstone, a kind of rock made up of tiny clay particles,
2014年，它发现了沉积的泥岩，一种由粘土微粒构成的岩石，
which were very similar to the ones it later found on Mount Sharp.
它和随后在夏普山发现的岩石非常相似。
And on Earth, mudstone is found in former lake beds and riverbeds.
在地球上，泥岩的发现地是从前的湖床和河床。
At the time, that wasn't enough evidence to definitively say, "Yes! There was totally a big old lake here!"
这次，我们没有足够的证据肯定地说“是的!这里曾经有一个很大的湖！”
But we did think water was probably flowing all throughout that area, and now,
但我们考虑过这里可能有水流过，现在，
thanks to some more investigating, we're pretty confident that big old lake was actually there.
幸亏有了更多的考察，我们非常确信这里曾有个大湖。
And because of Curiosity, we now know Mars used to have rivers, too.
因为“好奇号”，我们现在知道火星曾经也有河流。
Back in 2013, Curiosity found a bunch of conglomerates, which are basically some pebbles cemented together by sandstone, mudstone, or something similar.
回到2013年，“好奇号”发现了很多砾岩，它基本上是一些鹅卵石与砂岩、泥岩或类似的东西粘合在一起的产物。
What was really neat about these conglomerates was the shapes of the pebbles: They were smooth on all sides.
这些砾岩真正不可思议的地方是鹅卵石的形状：它们各面都是光滑的。
That happens when pebbles are subjected to eroding forces from every angle, like if they're suspended in a river.
鹅卵石只有从各个角度都受到侵蚀的时候才会这样，就像它们悬浮在河里一样。
So these rocks were direct evidence for rivers on ancient Mars!
所以这些岩石是古火星曾有河流的直接证据！
Curiosity also looked for the kinds of molecules that life needs.
“好奇号”也寻找生命所需的分子种类。
Life, as we know it, requires six basic elements: sulfur, phosphorus, oxygen, nitrogen, carbon, and hydrogen.
我们知道，生命需要六种基本元素：硫、 磷、氧、氮、碳和氢。
Carbon is at the heart of organic chemistry, but alone, it can't do much.
碳是有机化学的核心，但只有它没多大用。
When you add in the other elements, though, you get the molecules that work together to make life, DNA, proteins, sugars, you name it.
不过，你加入其他元素后就能组成分子 ，分子共同工作形成生命、脱氧核糖核酸、蛋白质、糖等，应有尽有。
In 2014, a set of papers was published in the journal Science that showed Curiosity found all of those elements,
2014年，发表在《科学》(Science)杂志上的一组论文显示，“好奇号”在钻入盖尔陨石坑的岩石中时，发现了所有这些元素，
as well as more complex molecules, when it drilled into the rock in Gale Crater.
也发现了更复杂的分子。
And in 2015, another paper was published showing even more organics in the same area.
2015年，发表的另一篇论文显示在同一区域有更多的有机物。
But that doesn't mean there actually was life on Mars. We don't have an answer on that yet.
但这并不意味着火星上确实有过生命。我们还没有答案。
But we do know that the raw materials are there, which is still kind of a big deal.
但我们知道这里有原材料，这仍然是一件大事。
And then there's the atmosphere.
然后就是火星上有大气。
Right now, Mars' atmosphere is pretty unimpressive, except when it whips up big dust storms.
现在，火星的大气丝毫不惹人注意，只除了它刮大沙尘暴的时候。
Mostly, it's just thin and cold.
大多时候，它只是稀薄冰冷的。
But Mars might have once had a thicker atmosphere, the kind that could have supported life.
但火星可能曾经存在过养育生命的稠密大气。
So Curiosity looked into it when that atmosphere thinned out.
所以，当大气变薄时，“好奇号”就开始研究它。
In 2013, the rover took samples of the atmosphere, measuring both the types of elements and the abundance of each element's isotopes.
2013年，探测器采集了大气样本，测量其元素的种类和每个元素同位素的丰富度。
Isotopes are different versions of the same element, they just have different masses,
同位素是同一种元素的不同形式，只是质量不同，
which corresponds to the number of neutrons they have.
这源于它们的中子数不同。
When scientists analyzed the data, they found that, for each element, there were a lot more heavy isotopes than they expected.
科学家们分析数据时发现，每个元素重同位素的数量比他们预想的要多。
Which was not good news when it comes to whether there was once life on Mars.
这对于寻找火星生命足迹不是什么好消息。
Heavier isotopes are usually less common than lighter ones,
重同位素通常比轻同位素少些，
so researchers don't think there just happen to be a bunch of heavy isotopes on Mars.
所以研究人员并不认为火星上恰巧有一堆重同位素。
The lighter isotopes had to go somewhere.
轻同位素一定去了哪儿。
When there aren't a lot of chemical reactions going on, heavy isotopes tend to hang out below the lighter ones,
当没有大量的化学反应时，重同位素倾向于悬在轻同位素的下方，
which happens because an isotope's mass affects its velocity and thermodynamics.
这是因为同位素的质量影响着它的速度和热动力。
That's probably how Mars lost its lighter isotopes.
这可能是火星失去轻同位素的方式。
Billions of years ago, the lighter isotopes moved upward in the atmosphere, closer to space, and were stripped away by solar winds,
数十亿年前，轻同位素在大气中上升，接近太空，然后被太阳风刮走了，
which left behind a thin atmosphere with a higher proportion of heavy isotopes.
使得留下的稀薄大气中重同位素的比例更高。
When scientists compare these measurements from Curiosity to really, really old Martian meteorites, like, almost 4 billion years old,
科学家们比较“好奇号”采集的样本和有40亿年之久的火星陨石的测量值时，
the isotope ratios are still very similar.
发现它们的同位素比率仍然很相似。
That suggests that most of this atmospheric loss took place sometime within the first 500 million years or so of Mars' history.
这表明大部分的大气损失发生在火星历史的最初5亿年左右。
So there was a relatively thick atmosphere, but only for a little while.
所以那时大气层比较厚，但只是暂时的。
That doesn't necessarily mean Mars isn't or never was habitable,
这并不一定意味着火星没有适居地或永远不适合居住，
just that it's been home to some extreme, low-pressure environments for a very long time.
只是在很长一段时间里，它一直都是极端、低压的环境。
From water to complex molecules to the atmosphere,
从水到复杂分子到大气，
Curiosity has made some amazing discoveries in five years, and it's still looking for more.
“好奇号”在五年里有许多惊人的发现，它仍会作更多的考查。
So here's to the next five years, li'l buddy!
所以兄弟，接下来的五年，
You're doing such a good job up there!
你在那里要工作出色！
Thanks for watching this episode of SciShow Space.
感谢您收看本期的太空科学秀。
For more on Curiosity's past and future, you can check out our video on "how long the Rover will last".
要想了解更多的“好奇号”的过去和未来，你可以点击“how long the Rover will last”这一期视频。
