科学美国人60秒 SSS 摧毁地球的小行星并没有那么容易（在线收听）

Busting Earth-Bound Asteroids Bigger Job Than We Thought

In the movie Armageddon, an asteroid the size of Texas is hurtling towards Earth. All seems lost, but then Bruce Willis sacrifices his own life to detonate a thermonuclear bomb on the asteroid. Then you hear this from mission control:

在电影《世界末日》中，一颗德克萨斯州大小的小行星正冲向地球。一切似乎都失去了，但随后布鲁斯·威利斯牺牲了自己的生命，在小行星上引爆了一枚热核炸弹。然后从任务控制中心可以听到:

Breaking a rock that big into two halves, that somehow miraculously dodge the Earth? A bit of Hollywood magic. But scientists are studying what would really happen in such a scenario.

把这么大的石头砸成两半，奇迹般地躲过了地球?似乎有点好莱坞的魔力。但是科学家们正在研究在这种情况下会发生什么。

"A big part of what we do is looking at how things break. Smashing things together and what happens after that." Charles El Mir is a mechanical engineer who studies planetary science at Johns Hopkins University.

我们所做的很大一部分工作就是观察事物是如何破裂的。物体撞击，然后会发生什么。”查尔斯·埃尔米尔是约翰·霍普金斯大学研究行星科学的机械工程师。

He and his colleagues modeled what might happen if you smashed up a 15-mile-wide asteroid, made of basalt. They started by assuming the asteroid has some tiny cracks already running through it, based on studies of real rock. Then, they struck the hypothetical space rock with another, smaller rock—just a mile wide—hurtling towards the asteroid at more than 11,000 miles per hour. When it hit, they tracked how stress waves propagated through the asteroid, and expanded the network of cracks.

他和同事们模拟了如果粉碎一颗由玄武岩构成的15英里宽的小行星会发生什么。根据对真实岩石的研究，他们首先假设这颗小行星已经有了一些微小的裂缝。然后，他们用另一块只有1英里宽的更小的岩石以每小时11000多英里的速度撞击假设中的太空岩石.当它撞击地球时，他们追踪了应力波是如何在小行星上传播的并扩展裂缝网。

Previous impact models predicted that an impact like that would completely pulverize the asteroid, basically turning it to sand. But not this new model. "What we're seeing, after the impact you have this big chunk of rock that was still held together, still not completely broken down, and this piece of rock creates its own gravitational field which attracts the particles that were ejected from it, and they start re-accumulating over it."

之前的撞击模型预测，这样的撞击会彻底粉碎小行星，基本上把它变成沙子。但这个新模型的结果不是这样。“我们看到的是，在撞击之后，这大块岩石仍然被绑在一起，还没有完全分解，这片岩石产生了自己的引力场，吸引着从岩石中喷射出来的粒子，它们开始在上面重新积累。

The scientists describe the model in the journal Icarus.

科学家们在《伊卡洛斯》杂志上描述了这个模型。

The work suggests asteroids might actually be harder to smash than we thought, meaning: "We might need to have a faster impactor, larger mass of impactor coming in, to be able to deflect it efficiently."

这项研究表明，实际上小行星可能比我们想象的更难撞碎，这意味着:“我们可能需要一个更快、更大质量的撞击器，才能有效地使其偏转。”

In 2022 NASA's Double Asteroid Redirection Test mission, or DART, will attempt to put all this knowledge to the test, by shoving a near-Earth asteroid off its path. No Bruce Willis required.

在2022年，美国宇航局的“双小行星重定向测试任务”(简称DART)将试图通过将一颗近地小行星推离其轨道，来测试所有这些知识。不需要布鲁斯·威利斯的理论。