Watery Asteroids Also a Source?
小行星上的水也是来源之一？
大角度：小行星！
Water has already been found on asteroids.
水已被发现在小行星。
Defend your planet from incoming asteroids.
保护地球抵御外太空的行星。
Asteroids May Have Brought Precious Metals to earth.
小行星可能把贵金属带到地球。
If there were no asteroids would there be no extinctions?
如果没有小行星，就不会有灭绝了吗？
No asteroids or comets are actually predicted to hit Earth.
没有任何小行星或彗星真的被预言会撞击地球。
It's most likely the result of a recent collision between two asteroids.
这很可能是两个小行星之间相撞产生的结果。
This is to save time and to reach some similarity between asteroids.
这是为了节省时间，也是为了让各个小行星之间有些共同点。
But asteroids were generally thought to be dry. Or at least frost-free.
不过，小行星被公认是干燥无水的，至少是不会结霜。
That is the reason for the search for asteroids with appropriate orbits.
这就是为何要寻找轨道合适的小行星的原因。
I hear that scientists are planning to study asteroids and meteors, right?
我听说科学家正计划研究小行星和陨石，对不对？
Asteroids and comets in nearby space pose a constant threat to our planet.
近地太空中的小行星和彗星们持续威胁着我们的星球。
I hear that scientists are planning to study asteroids and meteors, right?
学生：我听说科学家正计划研究小行星和陨石，对不对？
Apollo asteroids pose a threat to our planet as they routinely cross Earth's orbit.
阿波罗型小行星因定期地穿越地球轨道而构对地球的威胁。
And even if no killer asteroids are found, the money will not have been wasted.
即便没有发现毁灭性小行星，这笔钱也不会白花。
Large asteroids are relatively easy to spot because they reflect the most sunlight.
相对来说，大的星体更容易观测，因为他们会反射大部分日光。
These small impacts do little damage. It's the bigger asteroids that cause problems.
这些微小的冲撞破害性不大，真正造成麻烦的是个头较大的小行星。
These small impacts do little damage. It's the bigger asteroids that cause problems.
这些微小的冲撞破害性不大，真正造成麻烦的是个头较大的小行星。
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