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科学美国人60秒: 陨石含有比地球更古老的物质

所属教程:科学美国人60秒科学系列 更新:01-21
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Meteorite Contains Material Older Than Earth

陨石含有比地球更古老的物质

Sunday morning, September 28th, 1969, a fireball lit up the skies north of Melbourne, Australia.

1969年9月28日,星期天的早晨,一个火球照亮了澳大利亚墨尔本北部的天空。

“People were getting ready to go to church, and then they heard this loud sonic boom. Some of them saw the bright fireball in broad daylight, and people were surprised. They said, ‘What’s going on? Is there an airplane that came down? It sounded really dramatic.’ And then suddenly, shortly after that, there was a smell that was detectable over the whole area. People describe it as methylated spirits—a strong organic smell.”

“人们正准备去教堂,然后他们听到了巨大的音爆。他们中的一些人在光天化日之下看到了明亮的火球,人们都很惊讶。他们说,‘怎么回事?一架飞机坠毁了?听起来很戏剧化。“然后,不久之后,突然有一种气味在整个区域都可以闻到。人们把它描述为甲基化的灵魂——一种强烈的有机气味。”

Cosmochemist Philipp Heck of Chicago’s Field Museum describing the spectacular arrival of what’s now known as the Murchison meteorite, named for the village where it was found. A portion of the space debris now resides at the Field Museum. And Heck says it’s our best source of presolar stardust—meaning stardust older than the solar system and the sun itself.

芝加哥菲尔德博物馆的宇宙化学家菲利普·赫克描述了现在被称为默奇森陨石的壮观的到来,以发现它的村庄命名。部分太空碎片现在存放在菲尔德博物馆。赫克说它是太阳系前星尘的最佳来源——意思是比太阳系和太阳本身还要古老的星尘

“I call it a scientific treasure trove.”

“我称之为科学宝藏。”

Inside the meteorite is dusty debris left over from when stars slightly larger than our sun fizzled out. Over millions of years, those dust grains were battered by cosmic rays, which slightly altered their composition. Atoms of elements got broken down into smaller ones like neon and helium. Then some of that stardust was swallowed up within rocks—such as the Murchison meteorite—during the formation of our solar system. Those rocks served as time capsules, preserving the material for unimaginable ages.

在陨石内部是一些比太阳稍大的恒星熄灭后留下的尘埃碎片。在数百万年的时间里,这些尘埃颗粒受到宇宙射线的冲击,其组成略有改变。元素的原子被分解成更小的原子,比如氖原子和氦原子。然后,在我们太阳系形成期间,一些星尘被岩石吞噬,比如默奇森陨石。这些岩石充当了时间胶囊,将这些物质保存了很长的时间。

Previous astronomical observations have hypothesized that there was a “baby boom” of stars about seven billion years ago. By studying the Murchison grains’ elemental composition, Heck’s team was able to date 49 grains and found that two thirds of them were 4.6 to 4.9 billion years old.

之前的天文观测已经假设在大约70亿年前有一个恒星的“婴儿潮”。通过研究默奇森谷物的元素组成,赫克的研究小组确定了49颗谷物的年代,发现其中三分之二的谷物有46到49亿年的历史。

“And that all makes sense, because the parent stars—they formed seven billion years ago, and it took them about two to 2.5 billion years to evolve, become planetary nebula and become dust-producing.”

“这一切都说得通,因为母恒星——它们形成于70亿年前,它们花了大约20到25亿年的时间进化,形成行星状星云,并产生尘埃。”

The results are in the Proceedings of the National Academy of Sciences. Some of the grains are actually up to seven billion years old, making them the most ancient material on Earth—delivered here without notice, on a quiet Sunday morning, 50 years ago.

研究结果发表在《美国国家科学院院刊》上。事实上,有些谷物已经有70亿年的历史了,这使它们成为地球上最古老的物质。

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