研究發(fā)現(xiàn)，火星上有兩種水，它們可能來自不同的起源

研究發(fā)現(xiàn)，火星上有兩種水，它們可能來自不同的起源

An analysis of Martian meteorites shows that there are at least two different types of water contained in reservoirs on Mars, suggesting that the planet did not form in a similar way to Earth and may have obtained its hydrogen from outside forces.

對火星隕石的分析表明，火星上的水庫中至少含有兩種不同類型的水，這表明火星的形成方式與地球不同，可能是從外力中獲得了氫。

The Red Planet is composed of a core, mantle, crust, and atmosphere, which means that it evolved through geological processes much like Earth. Previous theories suggested that Mars also may have once had a global magma ocean, however, the planet lacks evidence of ever having plate tectonics and, without them, the crust would have served as a “physicochemical barrier” between the atmosphere and geological fluids contained within the mantle. Ancient river valleys and deltas suggest that Mars has a watery past, but today the atmosphere is too thin for liquid water to exist on the surface, according to NASA. Rather, it is held in ice form below the planet’s surface in the polar regions.

這顆紅色行星由地核、地幔、地殼和大氣組成，這意味著它的演化經(jīng)歷了與地球相似的地質(zhì)過程。先前的理論認(rèn)為，火星也可能曾經(jīng)有過一個(gè)全球巖漿海洋，然而，火星缺乏板塊構(gòu)造存在的證據(jù)，如果沒有板塊構(gòu)造，地殼將成為大氣和地幔內(nèi)地質(zhì)流體之間的“物理化學(xué)屏障”。據(jù)美國宇航局的說法，古老的河谷和三角洲表明火星有一個(gè)多水的過去，但如今的大氣層太薄，液態(tài)水不可能存在于火星表面。相反，它是以冰的形式存在于極地的行星表面之下。

But where this water came from – and how Mars came to be – has long been a mystery to scientists.

但是，這些水是從哪里來的，以及火星是如何形成的，對科學(xué)家來說，這一直是個(gè)謎。

That’s where researchers at the University of Arizona come in. To reconstruct the water history and the planet’s origin, scientists chemically analyzed two Martian meteorites known to have interacted with fluids contained below the surface of the planet: Northwest Africa 7034, or Black Beauty, and Allan Hills 84001. Specifically, two types, or isotypes, of hydrogen were found to exist within their contains. One form contained only a proton in its nucleus, which is known as “light hydrogen,” and the second both a proton and a neutron, also known as deuterium or “heavy hydrogen.”

亞利桑那大學(xué)的研究人員就是沖這個(gè)來的。為了重建水的歷史和地球的起源，科學(xué)家們對兩顆火星隕石進(jìn)行了化學(xué)分析，這兩顆隕石已知曾與地球表面以下的流體發(fā)生過相互作用：非洲西北部7034號，或稱“黑色之美”，以及艾倫·希爾斯84001號。具體地說，在他們的容器中發(fā)現(xiàn)了兩種類型的氫，或者說是同類型的氫。一種形態(tài)的原子核中只含有一個(gè)質(zhì)子，即所謂的“輕氫”，另一種形態(tài)的原子核中同時(shí)含有一個(gè)質(zhì)子和一個(gè)中子，也稱為氘或“重氫”。

On Earth, water held within rocks is unfractionated, meaning that it does not deviate much from ocean water. On the other hand, previous meteorite analyses have suggested that Mars is heavily fractioned and varies greatly.

在這顆星球上，巖石中的水是不分餾的，這意味著它與海水的差別不大。另一方面，之前的隕石分析表明，火星經(jīng)歷過嚴(yán)重分裂和很大的變化。

"The prevailing hypothesis before we started this work was that the interior of Mars was more Earthlike and unfractionated, and so the variability in hydrogen isotope ratios within Martian samples was due to either terrestrial contamination or atmospheric implantation as it made its way off Mars," said Jessica Barns, assistant professor of planetary sciences at the University of Arizona Lunar and Planetary Laboratory, in a statement.

杰西卡·巴恩斯說：“在我們開始這項(xiàng)工作之前，普遍的假設(shè)是，火星內(nèi)部更像地球，也更不實(shí)際，因此火星樣品中氫同位素比值的變化是由于火星離開火星時(shí)受到地球污染或大氣注入所致。”，亞利桑那大學(xué)月球和行星實(shí)驗(yàn)室行星科學(xué)助理教授在一份聲明中說。

Isotopic ratios from the meteorites fell halfway between those found on Earth and others seen in Mars’ atmosphere, an interesting discovery considering that Mars' atmosphere is being fractionated but the crust is staying roughly the same throughout the planet’s geological history. Further analysis found that there are also two different types of Martian volcanic rocks – enriched shergottites and depleted shergottites – that both contain water with different hydrogen isotope ratios.

隕石的同位素比值介于地球上發(fā)現(xiàn)的隕石和火星大氣中發(fā)現(xiàn)的隕石之間，這是一個(gè)有趣的發(fā)現(xiàn)，考慮到火星大氣正在被分餾，但地殼在整個(gè)地球的地質(zhì)歷史中基本保持不變。進(jìn)一步分析發(fā)現(xiàn)，火星上還有兩種不同類型的火山巖——豐富和貧瘠的鈣鐵礦含量——它們都含有不同氫同位素比率的水。

The two different types of hydrogen, which are described in Nature Geoscience, suggest that Mars has at least two different types of water that likely came from different sources. Over the planet's several-billion-year-history, two celestial objects with different water contents may have collided and never have mixed.

《自然地球科學(xué)》中描述的兩種不同類型的氫，表明火星至少有兩種不同類型的水，可能來自不同的來源。在火星數(shù)十億年的歷史中，兩個(gè)不同含水量的天體可能發(fā)生了碰撞，但從未混合過。