Comets were formed around the same time the Earth was formed.
彗星与地球大约同时形成。
我们需要研究更多的首星。
It's the first craft to visit two comets.
这是第一个访问两个彗星的飞船。
Comets are usually made of ice and rock.
彗星通常是由岩石和冰构成的。
Scientists have a particular interest in comets.
科学家对彗星很感兴趣。
Any school kid can tell you that comets are made of ice.
随便找个小学生都会告诉你，彗星是由冰组成的。
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。
Some material looks very similar to what is found in comets.
某些物质与其他星体中发现的物质十分相似。
Because if comets battered the moon, they probably hit the Earth, too.
因为如果彗星能够把水带到月球，同样很可能带到地球。
Comets move around the sun like planets, but in long oval course.
彗星象行星一样绕太阳运转，然而其轨道呈狭长的椭圆形。
Most comets are so dim that they cannot be seen by the naked eye.
大多数慧星都很暗，肉眼是看不见的。
Comets move around the sun like planets, but in a long oval pattern.
彗星像行星一样围绕太阳运转，但其轨道是长长的椭圆形状。
He has found more comets-22-than all but three other people in history.
他总共发现了22颗彗星，有史以来只有另外3个人超过他。
Once in deep space, it went though the same process of aggregating into comets.
进入外太空后，彗星形成的过程就和以前所知并无二致了。
However, most comets are too small or too faint to be seen without a telescope.
然而，大部分彗星都过小或过暗，只能用望远镜观察到。
Some scientists believe the water on the earth was brought here by comets.
有些科学家认为地球上水是由彗星带来的。
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。
Some scientists believe the water on the earth was brought here by comets.
地球上的生命源自陨石或彗星带来的分子吗？
All these missions have shown that there is still much to learn from comets.
这些任务显示出关于彗星我们还有很多需要探究。
Comets are conglomerations of ice, dust and rock from the early solar system.
彗星是早期太阳系中冰、灰尘和岩石的聚合物。
In the solar system all heavenly bodies, not except comets, move round the sun.
在太阳系里，包括彗星在内所有天体都绕日旋转。
Comets consist of "dirty ice", rather than solid rock, and so contain little iridium.
彗星是由“脏冰”所组成，而不是像小型那样由固体岩石组成，所以只含有少量的铱。
Comets consist of "dirty ice", rather than solid rock, and so contain little iridium.
彗星是由“脏冰”所组成，而不是像小型那样由固体岩石组成，所以只含有少量的铱。
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