隕石撞地球，讓地球上的生命成為可能

研究發(fā)現(xiàn)，隕石撞地球，讓地球上的生命成為可能

There’s been more discussion recently about protecting life on Earth from a devastating asteroid strike. But a new study suggests that space rocks actually made life possible on the Blue Planet.

最近有更多關(guān)于保護地球生命免受毀滅性小行星撞擊的討論。但一項新的研究表明，太空巖石實際上使藍色星球上的生命成為可能。

Researchers identified isotopes of selenium in rocks in Earth’s mantle and found identical isotope signatures inside certain meteorites, notably those from the outer solar system.

研究人員鑒定了地球地幔巖石中硒的同位素，并在某些隕石中發(fā)現(xiàn)了相同的同位素特征，尤其是那些來自太陽系外的隕石。

“We show that selenium isotopes record a signature of late accretion after core formation and that this signature overlaps only with that of the CI-type carbonaceous chondrites,” the study’s abstract states. “We conclude that these isotopic constraints indicate the late veneer originated from the outer Solar System and was of lower mass than previously estimated. Thus, we suggest a late and highly concentrated delivery of volatiles enabled Earth to become habitable.”

“我們的研究表明，硒同位素記錄了巖心形成后的晚期吸積特征，而這種特征只與ci型碳質(zhì)球粒隕石的特征重疊，”該研究的摘要稱。“我們得出的結(jié)論是，這些同位素限制表明，晚旋切層起源于太陽系外，其質(zhì)量低于此前的估計。因此，我們認為揮發(fā)性物質(zhì)的晚期和高度集中的釋放使地球變得宜居。”

The selenium isotopes were detected using a method that took samples from mantle rocks, previously brought to the surface from plate tectonic processes and measured.

硒同位素的檢測方法是從地幔巖石中提取樣本，然后從板塊構(gòu)造過程中帶到地表進行測量。

All of this means that selenium, as well as water and other building blocks for life, originated outside of Earth and came to the planet via comets or meteorites, a concept known as panspermia.

所有這些都意味著硒，以及水和其他構(gòu)成生命的元素，起源于地球之外，并通過彗星或隕石來到地球，這一概念被稱為生源說。

“According to our calculations, around 60 percent of the water on Earth today comes from this source. That is the only way oceans could eventually form,” said the study’s lead author, María Isabel Varas-Reus, PhD, in a statement. “This created the conditions for life on Earth to develop in its present form.”

“根據(jù)我們的計算，今天地球上大約60%的水來自這個來源。這是海洋最終形成的唯一途徑。“這為地球上的生命以現(xiàn)在的形式發(fā)展創(chuàng)造了條件。”

Panspermia is the hypothesis that life on Earth originated from microorganisms in outer space that were carried here unintentionally by objects such as space dust, meteoroids and asteroids, according to an article on NASA’s website.

根據(jù)美國宇航局網(wǎng)站上的一篇文章，“生源說”是一種假說，認為地球上的生命起源于外層空間的微生物，這些微生物是由太空塵埃、流星體和小行星等物體無意中帶到地球上的。

Technically speaking, there should be no selenium seen in the Earth’s mantle, since it is attracted to iron, Varas-Reus explained. As a result, it largely resides in the Earth’s core, which is “iron-rich,” Varas-Reus continued.

從技術(shù)上講，地球的地幔中不應(yīng)該存在硒，因為它被鐵所吸引，因此，在地球的核心是“豐富的鐵”，瓦拉斯魯斯解釋道。

However, the selenium that was found in the mantle must have come after the Earth’s core formed, a time period she estimates happened after the moon was also formed, between 4.5 billion and 3.9 billion years ago.

然而，在地幔中發(fā)現(xiàn)的硒一定是在地核形成之后，她估計這段時間發(fā)生在月球形成之后，即45億到39億年前。

It has long been suspected that meteorites brought elements from space and added them to Earth’s mantle, but Varas-Reus said researchers “thought they were meteorites from the inner solar system.”

長期以來，人們一直懷疑隕石將太空中的元素帶到地球的地幔中，但瓦拉斯-魯斯說，研究人員“認為它們是來自太陽系內(nèi)部的隕石。”

“So we were very surprised that the selenium isotope signature of the Earth’s mantle closely matched a certain type of meteorite from the outer solar system,” Varas-Reus added. “These are carbonaceous chondrites from the solar system beyond the asteroid belt, from the area of the planets Jupiter, Saturn, Uranus and Neptune.”

“因此，我們非常驚訝地發(fā)現(xiàn)，地球地幔的硒同位素特征與來自太陽系外的某種隕石非常相似，”瓦拉斯-魯斯道。“這些碳質(zhì)球粒隕石來自小行星帶之外的太陽系，來自木星、土星、天王星和海王星的區(qū)域。”

The study was published in the journal Nature Geoscience.

這項研究發(fā)表在《自然地球科學》雜志上。