Title:Earth Could Have Supported Continental Crust, Life Earlier Than Thought

The early Earth might have been habitable much earlier than thought, according to new research from a group led by University of Chicago scientists.

芝加哥大学科学家牵头的一组新研究显示，地球上的生命起源可能比任何人想象中都早。

Counting strontium atoms in rocks from northern Canada, they found evidence that the Earth's continental crust could have formed hundreds of millions of years earlier than previously thought. Continental crust is richer in essential minerals than younger volcanic rock, which would have made it significantly friendlier to supporting life.

通过计算加拿大北部岩石中的锶原子，他们发现有证据表明，地球大陆地壳可能比原先想象的早几亿年就形成了。大陆地壳比年轻的火山岩更富于基本矿物，这将使大陆地壳更为友好，可以维持生命。

"Our evidence, which squares with emerging evidence including rocks in western Australia, suggests that the early Earth was capable of forming continental crust within 350 million years of the formation of the solar system,"  said Patrick Boehnke, the T.C. Chamberlin Postdoctoral Fellow in the Department of Geophysical Sciences and the first author on the paper.  "This alters the classic view, that the crust was hot, dry and hellish for more than half a billion years after it formed."

帕特里克·博汉克说：“我们的证据证实了澳大利亚西部正在出现的包括岩石在内的证据，这些证据表明，在太阳系形成后3.5亿年，早期地球能够形成大陆地壳。"这改变了传统观点，即地壳在形成后超过5亿年是热、干燥、地狱。

One of the open questions in geology is how and when some of the crust–originally all younger volcanic rock–changed into the continental crust we know and love, which is lighter and richer in silica. This task is made harder because the evidence keeps getting melted and reformed over millions of years. One of the few places on Earth where you can find bits of crust from the very earliest epochs of Earth is in tiny flecks of apatite imbedded in younger rocks.

地质学的一个未决问题是地壳中最年轻的火山岩如何以及何时变成我们所了解的大陆地壳，而硅石中较轻而丰富的地壳。这项任务变得更为艰巨，因为证据在数百万年里不断被融化和改革。地球上为数不多的几个地方中，你可以从最早的地球时代找到地壳，其中一处是在小斑点磷灰石中埋入较年轻的岩石中。

Luckily for scientists, some of these  "younger"  minerals (still about 3.9 billion years old) are zircons–very hard, weather-resistant minerals somewhat similar to diamonds.  "Zircons are a geologist's favorite because these are the only record of the first three to four hundred million years of Earth. Diamonds aren't forever–zircons are,"  Boehnke said.

对于科学家来说，幸运的是一些“年轻”矿物（目前仍有39亿年历史）是锆石非常坚硬、耐气候的矿物，与钻石有点相似。博汉克说：“锆是地质学家最喜爱的，因为这是地球上前三到四亿年的唯一记录。钻石不是永远的锆石。

Plus, the zircons themselves can be dated.  "They're like labeled time capsules,"  said Prof. Andrew Davis, chair of the Department of Geophysical Sciences and a coauthor on the study.

另外，锆类本身也可以被注明日期：“它们喜欢贴上标记的时间胶囊，” 地球物理科学系主任Andrew Davis教授和一位研究组长说。

Scientists usually look at the different variants of elements, called isotopes, to tell a story about these rocks. They wanted to use strontium, which offers clues to how much silica was around at the time it formed. The only problem is that these flecks are absolutely tiny–about five microns across, the diameter of a strand of spider silk–and you have to count the strontium atoms one by one.

科学家们通常研究不同元素的变异，即同位素，来讲述这些岩石的情况，他们想用锶来揭示这些岩体在形成时存在多少二氧化硅。唯一的问题是，这些斑块是绝对微小的，大约五微粒跨越，蜘蛛丝的一缕直径，你必须逐一数数一数出锶原子。

This was a task for a unique instrument that came online last year: the CHicago Instrument for Laser Ionization, or CHILI. This detector uses lasers that can be tuned to selectively pick out and ionize strontium. When they used CHILI to count strontium isotopes in rocks from Nuvvuagittuq, Canada, they found the isotope ratio suggested plenty of silica was present when it formed.

这是去年联机研制的一种独特仪器：激光电离仪器或电离仪，该探测器使用激光，可以选择性地采集和离子束离子。当它们使用CHILI数计加拿大Nuvvuagittuq岩石中的同位素时，他们发现同位素比值表明，形成时存在大量二氧化硅。

This is important because the makeup of the crust directly affects the atmosphere, the composition of seawater, and nutrients available to any budding life hoping to thrive on planet Earth. It also may imply there were fewer meteorites than thought pummeling the Earth at this time, which would have made it hard for continental crust to form.

这一点很重要，因为地壳的构成直接影响大气层、海水的成分以及任何希望在地球上繁荣的新生活所能得到的养分。这也可能意味着流星子比当时认为袭击地球更少，这将使大陆地壳难以形成。

"Having continental crust that early changes the picture of early Earth in a number of ways,"  said Davis, who is also a professor with the Enrico Fermi Institute.  "Now we need a way for the geologic processes that make the continents to happen much faster; you probably need water and magma that's about 600 degrees Fahrenheit less hot."

恩里科·费尔米研究所的教授戴维斯说：“地壳早期在很多方面改变了早期地球的情景。”“ 现在我们需要一种使大陆更快地发生的地质过程的方法 ; 你们可能需要水和岩浆 , 这约为华氏 600 度的热水 。 ”

The study is also confluent with a recent paper by Davis and Boehnke's colleague Nicolas Dauphas, which found evidence for rain falling on continents 2.5 billion years ago, earlier than previously thought.

这项研究与戴维斯和博汉克的同事尼古拉·达普哈德(Nicolas Dauphas)最近的一份文件也有冲突。