科学美国人60秒 SSS 新模型旨在解决月球形成之谜（在线收听）

New Model Aims to Solve Mystery of the Moon's Formation

On July 20th, 1969, humankind finally set foot on the surface of the moon. Fifty years later a big mystery remains: how the heck the moon got there in the first place.

1969年7月20日，人类终于踏上了月球表面。五十年后，一个巨大的谜团依然存在:月球究竟是如何到达那里的?

For decades, the thinking has been that four and a half billion years ago a Mars-sized protoplanet smashed into the Earth. When the dust settled, our moon remained, forged from the debris of Earth and the other object.

几十年来，人们一直认为45亿年前一颗火星大小的原行星撞上了地球。尘埃落定后，我们的月球依然存在，它是由地球和其他物体的碎片锻造而成的。

Problem is, as scientists have taken more and more precise isotopic measurements of the Moon they've found that it's nearly identical in composition to the Earth—not some other object.

问题是，随着科学家们对月球进行越来越精确的同位素测量，他们发现月球与地球的成分几乎相同——而不是其他物体。

"A problem I've been advertising as an isotopic crisis." Jay Melosh studies planetary impacts at Purdue University. Now, he says, a new theory in the journal Nature Geoscience may at least point to a way out of that isotopic crisis of the moon’s chemical isotopes so closely resembling Earth’s.

“我一直把这个问题宣传为同位素危机。”杰伊·梅洛什在普渡大学研究行星撞击。现在，他说，发表在《自然地球科学》杂志上的一项新理论可能至少为解决月球化学同位素危机指明了一条出路。

Here's the idea. The authors, a team of Japanese scientists, write that maybe in those early days of the solar system the Earth was sloshing with oceans of magma. Then, when the Mars-sized object slammed into those molten seas, their models predict a lot more Earth-derived material got ejected into orbit in the form of scorching vapors.

想法是这样的。研究报告的作者是一组日本科学家，他们写道，也许在太阳系的早期，地球上到处都是岩浆。然后，当这个火星大小的物体撞击到那些熔融的海洋中时，他们的模型预测会有更多来自地球的物质以灼热的蒸汽的形式喷射到轨道上。

"Temperatures of tens of thousands of degrees. And so that expands at speeds that exceed the escape velocity of the earth, and in that way it injects material into orbit around the Earth."

“温度高达数万度。所以它的膨胀速度超过了地球的逃逸速度，这样它就把物质注入地球的轨道。”

That material rapidly coalesces, and bingo, you've got a moon. Melosh says there are still a few kinks to work out in the scenario. Still, he says, it's a step forward.

这些物质会迅速结合，然后，得到了一个月球。梅洛什说，在这种情况下，仍然有一些问题需要解决。不过，他说，这向前迈出的一步。

"Think of it as a major clue in a murder mystery or something like that. It could be a true clue toward the answer or it could be a deception—we don't know yet." So it could be that when astronauts started walking on the moon a half-century ago, they were really leaving footprints on the remains of the primordial Earth.

“你可以把它当做谋杀案或类似案件的主要线索。这可能是一个关于答案的真实线索，也可能是一个骗局——我们还不知道。”所以，当宇航员在半个世纪前开始在月球上行走时，他们可能真的在原始地球的遗迹上留下了脚印。