科学家们在争论一颗小行星是否要撞上地球。
Scientists were debating whether an asteroid was about to hit the Earth.
有个小行星正处于可能与地球发生碰撞的航向上。
最大的小行星是谷神星，其体积大约是月球的四分之一。
The largest asteroid is Ceres, which is about a quarter the size of the moon.
一些科学家假定，小行星撞击地球导致了恐龙的灭绝。
Some scientists hypothesize that the extinction of the dinosaurs resulted from the effects of an asteroid collision with Earth.
在很大程度上，Roids只是小行星和彗星的小碎片。
Roids are, for the most part anyway, they are just smaller bits of asteroids and comets.
这些小行星像类地行星一样，主要由岩石物质和金属构成。
These asteroids are like the terrestrial planets, in that they're composed mostly of rocky material and metals.
麦克·劳说：“向外迁移的地区使行星和小行星得以生存。”
"Regions of outward migration allow planets and planetoids to survive, " Mac Low said.
那么讲到流星体从何而来，我们就需要讨论下彗星和小行星。
So to talk about where meteorites come from, we need to talk about comets and asteroids.
在这种情况下，旋转小行星的轨道将非常缓慢地向太阳旋转。
In this case, the orbit of the rotating asteroid will very slowly spiral toward the sun.
地壳中含有的这种元素很少，但大多数小行星上的要多得多。
Earth's crust contains very little of this element, but most asteroids contain a lot more.
太阳系也有两类类似的物体，比行星还小——即小行星和彗星。
The solar system also has two analogous classes of objects, smaller than planets—namely, asteroids and comets.
最近的一项发现表明小行星非常多孔，这使得鲁宾的假设更加可信。
A recent discovery that asteroids are highly porous makes Rubin's hypothesis more plausible.
这一铱异常为阿尔瓦雷斯假说提供了强有力的支持，尽管小行星本身从未被发现。
This iridium anomaly offers strong support for the Alvarez hypothesis even though no asteroid itself has ever been discovered.
一颗小行星可能已经把美国毁灭了——而我可能几个小时内都没有听说这个消息。
An asteroid could have annihilated the USA—and I wouldn't have heard the news for hours.
小行星碰撞后的碎片可能会含有大量的铱，而大气洋流会把这些物质带到全球各地。
Debris thrown into the atmosphere by an asteroid collision would presumably contain large amounts of iridium, and atmospheric currents would carry this material all over the globe.
天文学家在距离地球不远处发现一颗小行星，它与地球在同一轨道上围绕太阳运行。
Astronomers have detected an asteroid not far from Earth, moving in the same orbit around the Sun.
我现在不打算深入讨论彗星和小行星了，但是我们稍后会再回到这个点上，讨论这方面的内容。
I'm not going to go into any depth on comets and asteroids now, but we'll come back later and do that.
穿过小行星带继续前进，我们进入了气体巨行星区域：木星、土星、天王星、海王星，所有这些都使地球看起来像个侏儒。
Moving on through the asteroid belt we enter the realms of the gas giant planets: Jupiter, Saturn, Uranus, and Neptune, all of which dwarf the Earth.
矛盾的是，虽然液态水所需的温度只存在于太阳系内部，但生命的关键组成部分，包括水本身，却主要存在于小行星带之外。
Paradoxically, while the temperatures required for liquid water exist only in the inner solar system, the key building blocks of life, including water itself, occur primarily beyond the asteroid belt.
怀疑派认为，一次撞击只会使小行星的整体温度上升很小，而且小行星在两次撞击之间会迅速冷却，从而无法积聚大量热量。
Skeptics have argued that a single impact would raise an asteroid's overall temperature very little and that asteroids would cool too quickly between impacts to accumulate much heat.
太阳是一个巨大的旋转系统的中心，这个旋转系统由九大行星、它们的卫星和无数的小天体组成，包括小行星、彗星和流星体。
The Sun is the hub of a huge rotating system consisting of nine planets, their satellites, and numerous small bodies, including asteroids, comets, and meteoroids.
鲁宾认为，小行星的热量可能来自小行星之间的碰撞。
Rubin suggests that asteroids' heat could have derived from collisions between asteroids.
这样大小的小行星即使受到冲击碎裂之后也会留下一个巨大的陨石坑。
An asteroid of this size would be expected to leave an immense crater, even if the asteroid itself was disintegrated by the impact.
编号为216Kleopatra的小行星正绕着太阳运行。
“小行星撞击？”亚茨拉菲尔说。
如果没有小行星，就不会有灭绝了吗？
实验也可以进行挖掘小行星。
水已被发现在小行星。
小行星上的水也是来源之一？
小行星上的水也是来源之一？
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