科学美国人60秒 SSS 小行星撞击令恐龙灭绝

This is Scientific American's 60-second Science, I'm Julia Rosen.

这里是科学美国人——60秒科学系列，我是朱莉娅·罗森。

We all know the story: 66 million years ago, a giant asteroid¹ crashed into Earth, killing² off three quarters of all species, including most of the dinosaurs³.

我们都知道这个故事:6600万年前，一颗巨大的小行星撞向地球，消灭了四分之三的物种，大多数的恐龙也包括在内。

Researchers suspect that the impact caused the extinction⁴ by kicking up a cloud of dust and tiny droplets⁵ called aerosols⁶ that plunged⁷ the planet into something like a nuclear winter.

研究人员怀疑，撞击是由一团被称为气溶胶的尘埃和小水滴组成的云引起的，这些云使地球突然进入了类似核冬天的状态。

“These components⁸ in the atmosphere drove global cooling and darkness that would have stopped photosynthesis⁹ from occurring, ultimately shutting down the food chain.”

“大气中的这些成分推动了全球变冷和进入黑暗，这会阻止光合作用的发生，最终关闭食物链。”

Shelby Lyons, a recent Ph.D. graduate from Penn State University.

谢尔比里昂斯，最近获得了博士学位，毕业于宾夕法尼亚州立大学。

But scientists have also found lots of soot¹⁰ in the geologic¹¹ layers deposited immediately after the asteroid impact.

但科学家们也在小行星撞击后立刻沉积的地质层中发现了大量煤烟。

And the soot may have been part of the killing mechanism¹² too—depending on where it came from.

煤烟也可能是杀戮机制的一部分——这取决于它的来源。

Some of the soot probably came from wildfires that erupted around the planet following the impact.

一些烟灰可能来自撞击后在地球周围爆发的野火。

But most of these particles would have lingered in the lower atmosphere for only a few weeks and wouldn’t have had much of an effect on global climate.

但这些粒子中的大多数只会在低层大气中停留几周，不会对全球气候产生太大影响。

But scientists hypothesize that soot may also have come from the very rocks that the asteroid pulverized¹³ when it struck.

但科学家们假设，烟灰也可能来自小行星撞击时粉碎的岩石。

If those rocks contained significant amounts of organic matter—such as the remains¹⁴ of marine¹⁵ organisms—it would have burned up on impact, sending soot shooting up into the stratosphere.

如果这些岩石中含有大量的有机物，比如海洋生物的残骸，那么它们就会在撞击中燃烧殆尽，并将烟灰喷到平流层中。

In that case, soot would have spread around the globe in a matter of hours and stayed there for years. And it would have radically¹⁶ altered Earth’s climate.

在这种情况下，烟灰会在几小时内扩散到全球各地，并在那里停留数年。它将从根本上改变地球的气候。

So Lyons and her team set out to identify the source of the soot.

因此，里昂斯和她的团队着手确定烟灰的来源。

They looked at chemicals known as polycyclic aromatic¹⁷ hydrocarbons¹⁸, or PAHs, which are another by-product¹⁹ of combustion²⁰.

他们研究了被称为多环芳烃的化学物质，这是燃烧的另一种副产品。

“You can find PAHs in meat or veggies that you grill²¹. You can find them from the exhaust of a car.

“你可以在烤肉或蔬菜中发现多环芳烃。你可以在汽车的排气管里找到它们。

You can also find them in smoke and debris²² from the wildfires today out west.”

你也可以在西部野火的烟雾和碎片中找到它们。”

PAHs are made up of fused rings of carbon atoms—think of chicken wire.

多环芳烃是由碳原子的熔合环组成的——想想铁丝网。

To determine the origin of the soot, the researchers looked at the structure and chemistry of the PAHs buried along with it.

为了确定烟灰的来源，研究人员观察了与烟灰一起掩埋的多环芳烃的结构和化学成分。

Specifically, the researchers looked for groups of atoms that stick off the rings like spikes²³.

具体来说，研究人员寻找的是像钉子一样从环上粘下来的原子群。

PAHs generated from burning wood don’t have many spikes, but PAHs from burning fossil carbon—like what would have been in the target rocks—have more.

燃烧木材产生的多环芳烃没有很多峰值，但燃烧化石碳产生的多环芳烃——比如目标岩石中的多环芳烃——有更多峰值。

Lyons and her team found that most of the PAHs deposited after the impact were spiky²⁴, which suggests that soot from the rocks hit by the asteroid played a major role in the mass extinction.

里昂斯和她的团队发现，撞击后沉积的大多数多环芳烃呈尖状，这表明小行星撞击岩石产生的烟尘在大规模灭绝中扮演了重要角色。

“There was more dust and more sulfate aerosols than soot, but soot is a stronger blocker of sunlight than either of those two. So a small amount of soot can drive large reductions in sunlight.”

“灰尘和硫酸盐气溶胶比煤烟多，但煤烟比这两种都更能阻挡阳光。所以，少量的煤烟就能大幅减少日照。”

The findings are in the Proceedings²⁵ of the National Academy of Sciences.

这项研究结果发表在《美国国家科学院院刊》上。

The results suggest that the devastation²⁶ of this very sooty asteroid impact may be due in part to a fluke of geography: the space rock smashed into the Gulf²⁷ of Mexico, where the sediments²⁸ were rich in organic matter.

研究结果表明，这次烟尘弥漫的小行星撞击造成的破坏可能部分是由于地理上的侥幸:太空岩石撞进了墨西哥湾，那里的沉积物中富含有机物。

They still are: the region produces large amounts of oil today.

现在仍然如此:该地区现在生产大量石油。

“Where it had occurred was likely one of the reasons that it led to a major mass extinction. It was kind of the perfect storm, or the perfect asteroid impact, I guess you could call it.”

“它发生的地方可能是导致大规模物种灭绝的原因之一。这是一场完美的风暴，我想你可以称之为完美的小行星撞击。”

Thanks for listening for Scientific American's 60-second Science. I'm Julia Rosen.

谢谢大家收听科学美国人——60秒科学。我是朱莉娅·罗森。

1 asteroid   

n.小行星；海盘车(动物)

参考例句：

• Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
• It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。

2 killing   

n.巨额利润；突然赚大钱，发大财

参考例句：

• Investors are set to make a killing from the sell-off.投资者准备清仓以便大赚一笔。
• Last week my brother made a killing on Wall Street.上个周我兄弟在华尔街赚了一大笔。

3 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

4 extinction   

n.熄灭，消亡，消灭，灭绝，绝种

参考例句：

• The plant is now in danger of extinction.这种植物现在有绝种的危险。
• The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。

5 droplets   

n.小滴( droplet的名词复数 )

参考例句：

• Droplets of sweat were welling up on his forehead. 他额头上冒出了滴滴汗珠。 来自辞典例句
• In constrast, exhaled smoke contains relatively large water droplets and appears white. 相反，从人嘴里呼出的烟则包含相当大的水滴，所以呈白色。 来自辞典例句

6 aerosols   

n.气溶胶( aerosol的名词复数 )；喷雾剂；（气体中的）浮粒；喷雾器

参考例句：

• Aerosols are present throughout the atmosphere. 气溶胶存在于整个大气层。 来自辞典例句
• Deodorants are available as aerosols or roll-ons. 除臭剂有喷雾装或滚抹装。 来自辞典例句

7 plunged   

v.颠簸( plunge的过去式和过去分词 )；暴跌；骤降；突降

参考例句：

• The train derailed and plunged into the river. 火车脱轨栽进了河里。
• She lost her balance and plunged 100 feet to her death. 她没有站稳，从100英尺的高处跌下摔死了。

8 components   

（机器、设备等的）构成要素，零件，成分； 成分( component的名词复数 )； [物理化学]组分； [数学]分量； （混合物的）组成部分

参考例句：

• the components of a machine 机器部件
• Our chemistry teacher often reduces a compound to its components in lab. 在实验室中化学老师常把化合物分解为各种成分。

9 photosynthesis   

n.光合作用

参考例句：

• In apple trees photosynthesis occurs almost exclusively in the leaves.苹果树的光合作用几乎只发生在叶内。
• Chloroplasts are the structures in which photosynthesis happens.叶绿体就是光合作用发生的地方。

10 soot   

n.煤烟，烟尘；vt.熏以煤烟

参考例句：

• Soot is the product of the imperfect combustion of fuel.煤烟是燃料不完全燃烧的产物。
• The chimney was choked with soot.烟囱被煤灰堵塞了。

11 geologic   

adj.地质的

参考例句：

• The Red Sea is a geologic continuation of the valley.红海就是一个峡谷在地质上的继续发展。
• Delineation of channels is the first step of geologic evaluation.勾划河道的轮廓是地质解译的第一步。

12 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

13 pulverized   

adj.[医]雾化的，粉末状的v.将…弄碎( pulverize的过去式和过去分词 )；将…弄成粉末或尘埃；摧毁；粉碎

参考例句：

• We pulverized the opposition. 我们彻底击败了对手。
• He pulverized the opposition with the force of his oratory. 他能言善辩把对方驳得体无完肤。 来自辞典例句

14 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

15 marine   

adj.海的；海生的；航海的；海事的；n.水兵

参考例句：

• Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

16 radically   

ad.根本地，本质地

参考例句：

• I think we may have to rethink our policies fairly radically. 我认为我们可能要对我们的政策进行根本的反思。
• The health service must be radically reformed. 公共医疗卫生服务必须进行彻底改革。

17 aromatic   

adj.芳香的，有香味的

参考例句：

• It has an agreeable aromatic smell.它有一种好闻的香味。
• It is light,fruity aromatic and a perfect choice for ending a meal.它是口感轻淡，圆润，芳香的，用于结束一顿饭完美的选择。

18 hydrocarbons   

n.碳氢化合物，烃( hydrocarbon的名词复数 )

参考例句：

• Hydrocarbons (HC), like carbon monoxide, represent unburned and wasted fuel. 碳氢化合物(HC)像一氧化碳一样，为未燃尽的和被浪费掉的燃料。 来自英汉非文学 - 环境法 - 环境法
• With this restricted frequency range it is not applicable to hydrocarbons. 这个较紧缩的频率范围不适用于烃类。 来自辞典例句

19 by-product   

n.副产品，附带产生的结果

参考例句：

• Freedom is the by-product of economic surplus.自由是经济盈余的副产品。
• The raw material for the tyre is a by-product of petrol refining.制造轮胎的原材料是提炼汽油时产生的一种副产品。

20 combustion   

n.燃烧；氧化；骚动

参考例句：

• We might be tempted to think of combustion.我们也许会联想到氧化。
• The smoke formed by their combustion is negligible.由它燃烧所生成的烟是可忽略的。

21 grill   

n.烤架，铁格子，烤肉；v.烧，烤，严加盘问

参考例句：

• Put it under the grill for a minute to brown the top.放在烤架下烤一分钟把上面烤成金黄色。
• I'll grill you some mutton.我来给你烤一些羊肉吃。

22 debris   

n.瓦砾堆，废墟，碎片

参考例句：

• After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
• Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上，导致蛀牙。

23 spikes   

n.穗( spike的名词复数 )；跑鞋；（防滑）鞋钉；尖状物v.加烈酒于( spike的第三人称单数 )；偷偷地给某人的饮料加入（更多）酒精（ 或药物）；把尖状物钉入；打乱某人的计划

参考例句：

• a row of iron spikes on a wall 墙头的一排尖铁
• There is a row of spikes on top of the prison wall to prevent the prisoners escaping. 监狱墙头装有一排尖钉，以防犯人逃跑。 来自《简明英汉词典》

24 spiky   

adj.长而尖的，大钉似的

参考例句：

• Your hairbrush is too spiky for me.你的发刷，我觉得太尖了。
• The spiky handwriting on the airmail envelope from London was obviously hers.发自伦敦的航空信封上的尖长字迹分明是她的。

25 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

26 devastation   

n.毁坏；荒废；极度震惊或悲伤

参考例句：

• The bomb caused widespread devastation. 炸弹造成大面积破坏。
• There was devastation on every side. 到处都是破坏的创伤。 来自《简明英汉词典》

27 gulf   

n.海湾；深渊，鸿沟；分歧，隔阂

参考例句：

• The gulf between the two leaders cannot be bridged.两位领导人之间的鸿沟难以跨越。
• There is a gulf between the two cities.这两座城市间有个海湾。

28 sediments   

沉淀物( sediment的名词复数 )； 沉积物

参考例句：

• When deposited, 70-80% of the volume of muddy sediments may be water. 泥质沉积物沉积后，体积的70-80％是水。
• Oligocene erosion had truncated the sediments draped over the dome. 覆盖于穹丘上的沉积岩为渐新世侵蚀所截削。