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This Episode is sponsored by the Ridge. Go to ridge.com/space and use promo code SPACE to get 10% off your next order.
本期节目由Ridge赞助播出。大家可浏览ridge.com/space，并通过使用优惠码SPACE来为订单减免10%。
It's been 50 years since humans last walked on the Moon, but that doesn't mean we've stopped exploring our closest neighbor.
人类上一次在月球行走是50年前，但这并不意味着我们停止探索月球这个最近的邻居了。
Countries from all over the world have sent robotic missions to study it, but none has been as important, or as successful, as NASA's Lunar Reconnaissance Orbiter.
世界各国已发送许多机器人任务来研究月球，但其中最重要也最成功的当属美国宇航局（NASA）的月球勘测轨道飞行器。
NASA launched the mission, often called LRO, in 2009 as part of its Vision for Space Exploration program.
NASA发射了该任务，也即LRO。时间是在2009年，该任务是“太空探索展望”项目的部分内容。
This was a long-term plan designed to guide the U.S. space program after the loss of the space shuttle Columbia.
这是一项长期计划，旨在引领美国太空项目，毕竟有哥伦比亚号失败的前车之鉴。
The goal with LRO wasn't just to do science, but to pave the way for a new era of human exploration.
LRO的目标不是做科学任务，而是为人类探索的新时代铺路。
And while we have yet to send people back to the Moon, we can definitely say the LRO has succeeded.
虽然我们还没能将人类送回月球，但我们绝对可以说LRO已经取得了成功。
The things it's teaching us about our closest neighbor are transforming the way we think about the Moon, and the information we're learning from it will make it much easier for future astronauts.
LRO让我们对月球有了新的了解，也转变了我们对月球的思考方式，我们了解的信息也会降低未来宇航员执行任务的难度。
So, in honor of all it's done so far, and to celebrate its 10th birthday, let's look back at three of LRO's biggest accomplishments.
所以，为了纪念LRO的功绩，也庆祝它10周年的生日，我们今天就回顾一下LRO的三个重要成就吧。
For one, this mission showed us that the Moon is not as dry as we used to think.
其一，该任务告诉我们月球并不是我们之前想象的那样干燥。
When researchers examined lunar rocks brought back by the Apollo astronauts, they turned out to be almost completely waterless; way drier than rocks found on Earth.
研究人员检测阿波罗号宇航员带回的石块时发现，这些石块几乎完全不含水分，比在地球上发现的石块要干燥的多。
That painted a picture of a pretty arid Moon. But some scientists suspected that frozen water might be hiding out in the Moon's deepest craters, which the Apollo program didn't visit.
这为我们描绘了一幅干燥月球的景象。不过，一些科学家认为，固态水可能隐藏在月球最深处的弹坑，而那里是阿波罗号未曾涉足的地方。
Those spots are so deep that they've never seen sunlight, and can have surface temperatures colder than Pluto, just 35°C above absolute zero.
这些地方很深，深到从来都不见天日，其表面温度比冥王星还低，只比绝对零度高35摄氏度。
Temperatures like that are too cold for water to sublimate away, and they make it possible for ice to survive in the vacuum of space.
这样的温度太低了，水是不可能升华的，而这样的环境里，冰是可以在真空环境下存在的。
But just because water could exist on the Moon didn't mean it had to be there.
不过，虽然水有可能存在于月球，但这种可能性并非100%。
To find out more, LRO's companion mission, called LCROSS, took one for the team.
为了了解更多信息，LRO的兄弟号LCROSS为团队又带回了一样物品。
It sent part of its rocket to smash into the Moon's Cabeus crater, sending a plume of surface debris into space.
LCROSS将部分石块猛撞在月球的卡比厄斯陨石坑上，将表面的一些残骸带进了太空。
Then, the LCROSS spacecraft and LRO studied the light from this material as it passed in front of the Sun, and researchers later found that the plume was full of grains of mostly-pure water ice.
随后，这两项任务一起研究了该物质发射出的光线，研究的时机是物质经过太阳前面的时候。随后，科学家发现，这缕物质中富含固态水的颗粒。
They pronounced this crater wetter than the Sahara.
他们认为该弹坑要比撒哈拉湿度高。
That might not sound very impressive, but it showed us that ice can accumulate on the Moon, and that this supposedly-arid place has pockets full of frozen water.
这听起来似乎没什么大不了，但这表明冰可以在月球上存续，也表明这个看起来像是不毛之地的地方富含固态水。
Someday, that water could be used to help astronauts on the Moon's surface.
总有一天，这些固态水可以用来帮助月球表面的宇航员。
But even if not, it's still pretty amazing that it's up there.
但即便不能，它存在于月球的消息已经十分惊人。
That's not the only thing LRO has uncovered in hidden ice, either.
而且这并非LRO在隐藏固态水中解锁的唯一秘密。
In 2016, scientists published another big discovery made by the orbiter: the Moon's ancient poles.
2016年，科学家发表了LRO的另一项重大研究：月球古老的极点。
Besides finding ice at today's poles, LRO found ice deposits offset by about 200 kilometers in opposite directions.
除了在极点处发现冰之外，LRO还发现了积冰，这些积冰与相反方向距离大概200公里的积冰相对称。
If you draw a line between them, it passes directly through the Moon's center.
如果在它们之间画一条线的话，会直接穿越月球中心。
Researchers interpreted this arrangement as evidence of the Moon's old poles, meaning the Moon used to spin on a different axis.
科学家认为这一点证明了月球存在古老的极点，这表明月球以前的转轴与现在不同。
Which isn't unheard of in the solar system, but still feels downright weird to think about.
这种现象在太阳系里也有出现过，只是每每想起还是觉得怪异。
Models show that that axis shifted around 3 billion years ago, most likely as mass moved around deep below the surface. This process was slow.
模型显示，月球的转轴在大概30亿年前出现了变动，那时候，月球围绕旋转的主要物质还处于月球表面下很深的地方。这个过程是很慢的。
The poles drifted only around 2 centimeters every century, but that was enough to knock the Moon off kilter by about 5°, like if Earth's axis shifted from the South Pole to Australia.
极点每个世纪大概只会飘移2厘米，但这样的微弱变化已经足以让月球失去大概5摄氏度的温差平衡了，就像地球的转轴从南极移到了澳大利亚一样。
As sunlight leaked into the once-shady areas, some of that old polar ice probably evaporated, but the rest traced out the path of the moving axis for us to uncover billions of years later.
日光流泻到了曾经阴暗的区域，导致一些沉积的极点冰层蒸发了，但其他部分没有受到转轴变动的影响，要等数十亿年后的我们去解谜。
Besides being cool, this finding is also significant because it helps us understand when the inside of the Moon was molten, which is important for studying how the Moon changed and evolved.
除了很酷之外，这个发现也意义重大，因为该发现帮助我们理解了月球内部何时融化的，这一点很重要，有助于我们研究月球是如何变迁演化的。
I mean, it doesn't give us a very specific estimate, but you have to start somewhere!
虽然并没有提供准确的估测，但至少让我们有了着手点呀！
Finally, although LRO is meant to study the Moon, it's actually taught us a lot about the entire solar system.
最后一点是：虽然LRO本来是要研究月球的，但它也让我们了解了很多有关整个太阳系的知识。
For instance, it took enough images for scientists to create a detailed, billion-year-long timeline of large asteroid impacts on the Moon.
比如，它拍摄了足够的照片，供科学家创建长达数十亿年的详细时间线，了解了大型小行星对月球的影响。
And this January, scientists reported that that timeline revealed something strange: Asteroid collisions seem to have more than doubled around 290 million years ago.
而且，今年1月，科学家在报告中指出，时间线揭秘了奇怪的事情：小行星碰撞似乎在大概2.9亿年前次数加倍了。
While that's interesting by itself, that also tells us something surprising about Earth.
虽然这件事本身很有趣，但也让我们了解了关于地球的惊人发现。
Scientists have known for a while that Earth has surprisingly few craters older than 300 million years, but they'd always assumed that the craters had just eroded away.
科学家此前已经知道地球上有一些弹坑的历史有3亿年以上，但他们一直以为这些弹坑已经逐渐减弱了。
Now, LRO is telling us that these aren't just gaps in the record, there were simply fewer impacts back then than the period that followed.
如今，LRO告诉我们，记录其实有缺口，因为那个时期的碰撞其实比后来少。
Scientists still don't know exactly what happened 290 million years ago, but one idea is the sudden bombardment might point to large collisions in the asteroid belt between Jupiter and Mars.
科学家依然还不知道2.9亿年前发生了什么，但他们有一个想法是——突然的爆炸可能是因为木星和火星之间的小行星带发生了大型碰撞。
Whatever it was, though, the scars on the Moon point to some major event in the distant past.
不管怎样，月球上的伤疤都告诉我们——古老的过去一定发生了什么大事。
And figuring out what it was would help us continue to understand how the solar system has changed over its lifetime.
了解这番过去会帮助我们继续理解太阳系的演变过程。
Also, on a much broader note, cratering rates on the Moon are also used to determine the ages of surfaces all around the solar system.
而且，从更广阔的角度来说，月球出现的弹坑也可以用来判断太阳系里所有星体的年龄。
Like, when scientists first saw Pluto's smooth surface, they assumed it was young because it doesn't have as many craters as the old lunar surface.
比如，当科学家首次观测冥王星光滑表面的时候，他们就认为冥王星年龄很小，因为冥王星的弹坑没有古老月球表面的多。
So the more we understand about the Moon's craters, the more we can infer about all the other objects out there.
所以，我们对月球弹坑的了解越多，我们就越能推断其他星体的信息。
Of course, even though LRO has taught us so many specific things over the last decade, it isn't valuable just because of those discoveries.
当然了，即便LRO让我们了解了过去10年间如此详细的信息，它也不知因为如此而有价值。
LRO is especially important because it lives around the Moon.
LRO的重要性尤其体现在它就在月球附近。
That means that, if scientists find something interesting, they can ask questions and get answers without having to wait for a new mission, which is pretty unusual in planetary science.
这意味着，如果科学家发现了有趣的事情，他们就可以先发出疑问，然后获取答案，而不用等新任务发射后才能获取答案了。这在行星科学中是很少见的现象。
Also, as much as space exploration is always pushing new horizons, LRO has shown us that there are still endless things to explore right here in our neighborhood.
此外，太空探索永远在突破新的边界，所以LRO也向我们展示了地球附近有无穷的信息可以探索。
And even closer to home, sometimes we get bogged down with all the stuff we carry around, and we need to trim down.
在离地球更近的地方，有时候，我们会陷入困境，需要删减信息。
We all carry around useless stuff. Random receipts, hotel room keys, spent gift cards.
我们都会携带一些无用的信息，比如随时可能获得收据、酒店房门钥匙、花掉的礼物卡。
The Ridge helps you carry less, but also, have what you need.
Ridge可以帮助我们携带更少的东西，但都是必要的东西。
They help you streamline your life by turning the things you carry, like backpacks, phone cases, and wallets into tools for better living.
Ridge帮助我们精简生活，将携带的物品，比如背包、手机壳、钱包变成提高生活质量的工具。
The Ridge wallet has over 30,000 5-star reviews.
Ridge钱包有3万多个5星评价哦。
There's a lifetime warranty, but if you don't love it, there are also free returns.
这可是一生的保证，但如果大家不喜欢的话，可以免费退货。
Get 10% off today with free worldwide shipping by going to ridge.com/space, that's ridge.com/space, and use the code SPACE.
今天可以登录ridge.com/space获得10%的减免，只需要使用优惠码SPACE即可。
You can find the link in the video description.
链接在视频描述中。
And if you check them out, it also supports us too, so thanks!
如果观众朋友们点击了，也是对我们节目的支持。谢谢大家！
