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Meteorites hold a special place in astronomy because they represent basically the only part of the universe beyond Earth that we can actually touch.
陨石在天文学中地位特殊，因为基本上可以说，陨石是地外之外我们可以实际触碰到的唯一物体了。
Every one has a story to tell, but some of those tales are more curious than others.
每个陨石都有自己的故事，但个别陨石的故事要比其他陨石更精彩。
So here are 3 of the weirdest meteorites we’ve ever found and what we learned from them.
下面介绍我们发现的最奇怪的3颗陨石，以及我们从这3颗陨石身上学到的东西。
Our first example isn’t actually just one meteorite, but a whole category.
第一颗陨石其实不算严格意义上的一颗陨石，而是包罗万象。
About a quarter of all meteorite samples show certain distinctive signs of being sculpted by the atmosphere as they fell to Earth.
近1/4的陨石样本表明，陨石在坠入地球的过程中会因大气层而改变成独特的造型。
The most striking have a special cone-like shape scientists call oriented meteorites.
其中最让人印象深刻的莫过于一颗特殊圆锥形的陨石了，科学家称之为有特定朝向的陨石。
After the white-hot intensity of hurtling through Earth’s atmosphere, most meteorites end up looking like weird chunks of rock.
在以白热化状态坠入地球大气层的过程中，大多数陨石最后看起来都会像形状奇怪的石块。
But the oriented ones are kind of comparable to the conical nose of an airplane, you can tell which way they were pointed as they fell.
但这类陨石的形状类似于飞机圆锥形的机头。
Astronomers have known about oriented meteorites for a long time, but they didn’t really know how this cone shape formed or why it only happens some of the time.
很久之前，科学家就知道了这类陨石的存在，但他们不知道这种圆锥的形状是如何形成的，也不知道其中的原委。
But a paper published in 2019 has finally shed some light on the situation.
但2019年发布的一篇论文对人们有所启示。
The researchers recreated the flight of a meteorite.
论文的几位作者重新模拟了陨石飞行的过程。
But instead of using a lump of rock falling through the sky, they used lumps of aluminum falling through water.
不过，他们没有用一块石头从天上坠落来进行模拟，他们的做法是让铝块从水中下落。
And cone-shaped lumps tended to fall in a relatively straight path without fluttering or tumbling.
圆锥形块状物体在下落时倾向于走相对直的直线，不会东倒西摇或者翻滚之类的。
This tells us that once they’d been eroded into a cone shape, oriented meteorites had relatively stable trajectories as they traveled through the atmosphere, letting that cone shape remain intact.
这就让我们知道——一旦这类陨石被腐蚀成了圆锥形，那么它们在穿过大气层的时候，路径就会相对稳定，圆锥形会保持不变。
But that kind of path isn’t guaranteed; most of the time, things tend to tumble head over heels.
但路径是无法保证的；大多数时候，这样的物体会头朝下。
So how did these meteors remain stable as they fell?
所以，流星在下落的时候是如何保持稳定的呢？
The authors also found that if an incoming “meteor” has an angle that’s too narrow, it bounces around, causing it to break up or erode too unevenly to form a cone.
本文的几位作者还发现，如果即将到来的陨石角度太窄的话，它就会弹来弹去，会很容易断裂或者各处腐蚀程度不同——无法形成圆锥。
And if the angle is too wide, it’ll end up fluttering back and forth like paper falling through the air, which also leads to uneven erosion and no pretty cone.
而如果角度太宽的话，就会来回点播，像纸在空中飘散一样。这样也会导致各处腐蚀程度不同，形成的圆锥也不会是完美的圆锥。
Only if the nose makes an angle of about 60 to 100 degrees will it fly straight the whole way down and become an oriented meteorite.
只有在锥顶成大概60-100度的时候，才会以直线飞行下落，并最终形成这类陨石。
But meteorites aren’t just space brought to Earth.
但陨石不只是从太空来到地球的东西而已。
They’re also pieces of the past that have survived to the present.
陨石也代表着遥远的过去。
One group, called the L-chondrites, is particularly intriguing because they all seem to have come from the same parent body at about the same time.
有一类陨石叫L-球粒状陨石，这类陨石尤为有趣，因为这类陨石似乎都是同时自同一个母体。
And this isn’t just a few samples, nearly all known meteorites are classified as chondrites, and up to 40% of those are L-chondrites.
这次不只是样本了，因为在定性为球粒状陨石的陨石中，高达40%都是L-球粒状陨石。
Many have been found in southern Sweden, embedded in limestone that’s about 470 million years old.
有很多L-球粒状陨石是在瑞典南部发现的，他们钳在有近4.7亿年历史的石灰岩中。
One meteorite from this region, though, sticks out like a sore thumb.
来自该区域的一块陨石尤为特别。
It’s called ?sterplana 065 and, not only is it not an L-chondrite, it doesn’t resemble any other known meteorite.
它叫?st 65，它不仅是L-球粒状陨石，而且它跟目前已知的其他陨石都不像。
One way to differentiate between meteorites is by looking at the isotopes of the elements it contains.
区分陨石的一种方法是：观测其中的同位素。
Isotopes are atoms of the same element with a different number of neutrons in their nuclei.
同位素是相同元素的原子，只是原子核中的中子数量不同。
The ratio of different isotopes in a substance works kind of like a fingerprint to identify where it might’ve come from.
不同同位素在物质中的比例就像足迹一样，让人可以辨认出它的来源。
When scientists examined the oxygen and chromium isotopes from ?st 65, they found ratios very different from the L-chondrites or any other known meteorite.
科学家从?st 65上检测到了氧和铬的同位素，其比例跟L-球粒状陨石等已知陨石的比例迥然不同。
That suggests that ?st 65 comes from a totally different space object than other meteorites we’ve recovered.
这表明，?st 65的母体跟其他陨石的母体不同。
So if it’s so different, why was ?st 65 found mixed in with a bunch of L-chondrites?
所以，如果?st 65如此不同，那为什么发现它的时候，也掺杂着很多的L-球粒状陨石呢？
Scientists think that if the L-chondrites all came from the same destroyed asteroid, ?st 65 might be a chunk of the object that did the destroying.
科学家认为，如果L-球粒状陨石都来自于同一颗破损了的小行星，那么?st 65可能就是造成破坏的那个罪魁祸首。
They collided violently in space only to rest in peace together on Earth.
他们在宇宙中激烈碰撞，最后跟地球和平共处。
Our final meteorite is unique for both how we found it and what it was hiding inside.
最后一颗陨石，我们发现它的方式和它其中隐藏的东西都很特别。
It’s called Almahata Sitta and it was the first meteorite to be detected before it hit Earth.
这颗陨石名为Almahata Sitta，这是第一颗在与地球撞击之前就被人类勘测到的陨石。
Astronomers even predicted approximately where it would land, which allowed geologists and volunteers to find and pick up the fragments.
天文学家甚至预测出了它大概的着陆位置，因此，地质学家和志愿者们也就能找到陨石碎片了。
And when they cracked open some of the pieces, the scientists found giant diamonds hiding inside.
科学家打开其中一些碎片，发现里面有大块的金刚石。
Well, not giant giant diamonds, but bigger than they would have expected.
不过，也不是超大啦，只是比预期想的要大。
See, diamonds in meteorites aren’t actually that surprising.
所以，在陨石中发现金刚石也不是很让人意外。
Asteroids often contain carbon, and microscopic diamonds are created all the time as they slam into one another.
陨石通常含有碳，在彼此撞击的时候，会一直形成金刚石。
But a sudden impact can’t form a large diamond, for that, you need lots of pressure over long periods of time.
不过，突然的冲击是无法形成大块金刚石的，因为金刚石的形成需要长期的压力作用。
Like the conditions you’d find deep inside a planet.
就好像你会在一颗星星内部深处发现的情况一样。
Diamonds often contain impurities in the form of minerals trapped inside their structure.
金刚石里通常包含矿物杂质。
Since we know how these minerals form, we can infer what conditions were like where the diamonds were forming.
由于我们知道这些矿物质形成的方式，所以我们可以推断出金刚石形成时的条件是怎样的。
For instance, quartz crystallizes at a relatively low pressure and temperature, while olivine forms only under extreme conditions.
比如，石英会在低压低温下结晶，而橄榄石则只会在极端条件下形成。
This is just because they’re made out of different stuff.
这只是因为它们的组成材质不同。
Sometimes minerals can even take on different structures depending on the conditions of their formation.
有时候，矿物质的结构也不同，这取决于它们的形成条件。
That’s why we have both diamond and graphite, even though both are entirely carbon.
因此，我们有金刚石和石墨，虽然它们都是完全由碳组成。
Almahata Sitta contains chromite, some phosphate minerals, and some iron-nickel sulfides.
Almahata Sitta中含有铬铁矿、一些磷酸盐矿物、一些铁镍硫化物。
Their chemical structures could only form under a pressure of at least 20 gigapascals, which is really high.
这些化学结构只会在至少20吉帕斯卡的压强下形成，这是很高的压强。
That tells us that the object they formed inside of was likely at least the size of Mercury, or maybe as big as Mars.
这也让我们知道——它们内部形成的物体很有可能至少是跟水星或者火星差不多大小的。
Since Mercury and Mars are definitely still around, Almahata Sitta probably came from inside a primordial planet that was destroyed in the chaos of the early solar system, a planet that never quite made it.
因为水星和火星都离我们不远，所以Almahata Sitta很有可能来自于某颗原始行星内部，这颗行星在太阳系形成初期的混沌环境下受到破坏，还在萌芽就消失了。
Which makes this rock from space as old as the Earth itself!
所以这颗陨石和地球差不多年龄！
So the next time you look up and see a shooting star, just think, Hey, that thing could be chock full of diamonds!
所以，下一次仰望天空并看到飞逝的星星时，要想到：嘿，这里面可能有大量金刚石哦！
Or maybe not. But either way, it could teach us something we never knew before.
不过也可能没有。不过不管实情是哪一种，都让我们了解了之前不知道的知识。
Thanks for watching this episode of SciShow Space.
感谢收看本期的《太空科学秀》。
Before you go, since you’re here and we know you like space, we’d like to draw your attention to September’s DFTBA pin of the month, which is this awesome retro take on the Viking lander.
在说再见之前，考虑到大家已经看到了这里而且大家都是太空迷，所以想介绍一下9月的DFTBA特惠码，这里会回顾海盗号的精彩历史哦。
This is a pre-order for a pin that will ship in October, and once September ends, they’re gone forever, so get them while you can.
机不可失时不再来，9月结束后，这次就没机会啦。
But don’t worry, we’ll have another great space pin next month.
不过别担心，10月也有很棒的特惠码。
Check it out at dftba.com or the merch shelf right below this video!
在dftba.com或者视频下方的特惠区都可以查看！
