Ancient Australian rocks may shed new light on the birth of the moon

古老澳大利亚岩石的出现将为探索月球的诞生提供新的线索

Some of Earth's oldest rocks buried deep in Western Australia may hold new clues about the dramatic event that gave rise to our moon.

一些深埋在地球西澳大利亚上最古老的岩石可能暗示着关于我们月球诞生的这个戏剧性事件的新线索。

In a new study led by the University of Western Australia (UWA), researchers analyzed 3.7-billion-year-old feldspar crystals found within magmatic anorthosite rocks from the Murchison region — among the oldest surviving pieces of Earth's crust — to uncover chemical fingerprints from our planet's earliest days. These anorthosites are particularly intriguing because while they're very common on the moon, they are rarely found on Earth, hinting at a deep connection between the two worlds, according to a statement from UWA.

在由西澳大利亚大学（UWA）引领开展的的一项新的研究中，研究人员研究了在默奇森地区岩浆斜长岩中发现的37亿年前的长石晶体——现存于地球最古老的地壳碎片之一——揭示了我们星球早期的化学指纹。根据UWA的一份声明显示，这些斜长岩特别有趣，虽它们在月球上非常常见，但在地球上极少被发现，这暗示了两个星球之间的深层联系。

"The timing and rate of early crustal growth on Earth remains contentious due to the scarcity of very ancient rocks," Matilda Boyce, lead author of the study and Ph.D. student at UWA, said in the statement. “We used fine-scale analytical methods to isolate the fresh areas of plagioclase feldspar crystals, which record the isotopic 'fingerprint' of the ancient mantle."

“由于稀缺极其古老的岩石，早期地球地壳生长的时间和速度仍存疑，”该研究的主要作者、博士玛蒂尔达·博伊斯(Matilda Boyce)在西澳大学演讲中表示,“我们用精细的分析方法分离出斜长石晶体的新鲜区域，这些晶体记录了远古地幔的同位素‘指纹’。”

Anorthosite rocks formed when molten magma slowly cooled deep beneath the surface, allowing large plagioclase feldspar crystals to grow and lock in chemical clues about the environment in which they formed. Because these ancient rocks have remained remarkably intact for billions of years, isotopic dating reveals when the minerals solidified, unlocking a direct glimpse into Earth's earliest crust and our planet’s infancy.

斜长岩是地表深处的熔融岩浆在缓慢冷却时形成的，使大型斜长石晶体生长并锁定有关其生成的化学环境线索。因为这些古老的岩石数十亿年来一直保持着非常完整的形态，同位素测年揭示了矿物何时凝固，从而直接一瞥地球最早的地壳和我们星球的婴儿期。

Using this method, the team was able to measure isotopic ratios that reveal what Earth's mantle and crust looked like billions of years ago. Their results suggest that continental growth didn’t begin immediately after the planet formed, but rather started later, around 3.5 billion years ago — nearly a billion years after Earth's birth.

使用此法，研究小组能够测量其同位素比率，揭示数十亿年前地球地幔和地壳的样子。他们的研究结果表明，大陆的生长并不是在行星形成后立即开始的，而是在更晚的时候才开始的，大约在35亿年前——地球诞生后约10亿年。

Even more striking, the researchers found that the isotopic signatures from the Australian rocks closely resemble those found in lunar samples collected during NASA's Apollo missions. That chemical link supports the leading "giant impact" theory for the moon's formation, in which a Mars-size object slammed into early Earth about 4.5 billion years ago, ejecting material that eventually coalesced into the moon.

更引人关注的是，研究人员发现澳大利亚岩石的同位素特征与美国宇航局阿波罗任务期间收集的月球样本中发现的同位素特征非常相似。这种化学联系为月球形成的主要“巨大撞击”理论提供大力支持，即大约45亿年前，一个似火星大小的物体撞击了早期地球，喷射出的物质最终合并成月球。

Because intact rocks from this ancient era are so rare, the discovery offers a unique opportunity to peer directly into Earth's formative past. These ancient minerals may preserve a record of the chemical mix left behind by that cataclysmic collision — a link between the infant Earth and its newly formed satellite.

因古老时代的完整岩石十分罕见，这一发现提供了一个特别的机会来直接窥视地球的形成历史。这些古老的矿物可能保存了那场灾难性碰撞留下的化学混合物的印记——早期地球和由它新形成的卫星之间的联系。

"Our comparison was consistent with the Earth and moon having the same starting composition of around 4.5 billion years ago," Boyce said in the statement. "This supports the theory that a planet collided with early Earth and the high-energy impact resulted in the formation of the moon."

博伊斯说：“我们将地球和月球进行比较，发现在大约45亿年前具有相同的起始成分。”这支持了行星与早期地球相撞，高能撞击后形成月球的理论。”

The study, conducted with collaborators from the University of Bristol, the Geological Survey of Western Australia and Curtin University, was published Oct. 31 in Nature Communications.

这项研究由布里斯托尔大学、西澳大利亚地质调查局和科廷大学的合作者进行，发表在10月31日的《自然通讯》上。