The orbits comets take sometimes end with them colliding with planets and their moons.
一些在轨彗星有时会以与行星或其卫星发生碰撞的形式走向终结。
Do we have an ethical duty to respect and preserve the natural environments of neighboring planets and their moons?
我们有一个道德义务，尊重并维护邻近行星及其卫星的自然环境吗？
Data and photographs from both probes revealed new details about these giant planets, their moons, and their rings.
两枚探测器发回了各种数据及照片，揭示了巨大行星及其卫星的细节。
It is an easily provable fact that with only chemical rockets, our ability to explore the outer planets and their moons is hindered.
如果仅仅使用化学燃料火箭，我们探索外层空间行星及其卫星的能力将受到限制，这是不难证明的事实。
Our planet Earth is one of nine planets which move round, or orbit, the Sun. The Sun, planets, and their moons form the solar system.
我们的地球是围绕太阳按轨道运行的九大行星之一。太阳、行星及行星各自的卫星构成了太阳系。
In time, we will want to dispatch spacecraft that will go into orbit around these alien planets, land robots on their moons, and even return rock and soil samples back to Earth.
迟早，我们将发送飞船进入环绕那些陌生行星运转的轨道，让机器人在它们的卫星上降落，甚至将岩石和土壤样品送回地球。
Eventually, we will want to send humans to their moons, on at least a couple of which liquid water - the fundamental requirement for life as we know it - is believed to be abundant.
最终，我们要将人类送到这些行星的卫星上去，至少送到据信有大量液态水存在的几个卫星上去——我们知道，液态水是生命的基本需要。
Alternatively, a craft could fly to one of their moons to collect rock samples and also accumulate hydrogen, by separating water obtained from melted ice, for the trip back to Earth.
另外，飞船可以飞到行星的一个卫星上采集岩石标本，还可以通过离析冰水以积累氢，为返回地球补充燃料。
The images have been scaled to represent the true relative sizes of the four moons and are arranged in their order from Jupiter.
图片经过按比例缩放以示四个卫星的真实的相对尺寸，并按它们据木星距离的顺序排列。
Moons are generally thought to form in one of two ways - either by coalescing from the same cloud of debris as their parent planet, or as wandering objects captured by the parent's gravitational pull.
卫星通常被认为形成于两种途径：一是由它们母星的同性云状碎片合并而成，一是被母星重力抓住的游离天体。
Four hundred years ago, Galileo raised his homemade spyglass to the sky and spotted four of Jupiter's moons, revealing that other planets could have their own lunar companions.
四百年前，当伽利略将自制的天文望远镜对向夜空时，他发现了木星的四个卫星，从而证实其它行星也会有自己的卫星。
Such large moons could form on their own and later be captured by a more massive planet's gravity to become a satellite.
这样大小的卫星可以自己首先形成，然后被一个更大体积的行星的引力所捕获成为它的卫星。
The planets and the major moons have all been squeezed and heated by gravity and pummeled by giant impacts, erasing much of their history.
那时，行星和一些主要的卫星承受着由重力造成的挤压加热以及巨大冲击造成的击打，这清除了它们许多的历史痕迹。
Most moons with irregular orbits are thought to be former comets or asteroids captured by their parent planet's gravity, and that may be Nereid's story too.
大多数有着不规则轨道的卫星被认为是被恒星的重力所吸引住的彗星或者小行星，并且海卫二可能也是这样的。
Under the new thinking, astronauts could barnstorm or circle the moon, Mars and Mars' twin moons, deploying probes to do their rock-collecting and experiments for them.
根据这种新思维，宇航员可以围绕月球、火星和火星的两颗卫星飞行，同时部署探测器为他们进行岩石采集和试验工作。
Colossal impacts in the outer reaches of the solar system may have bowled over remote, frozen moons, leading to vast cracks across their surfaces, research now suggests.
研究现在认为，太阳系外围的巨大碰撞可能击倒了遥远的冷冻的卫星，导致月球表面的巨大裂缝。
Our gods had horns on their heads, or moons, or sealy fins, or the beaks of eagles.
我们的神明头上长角、或月亮、或海豹鳍、或鹰喙。
Here, under her few square yards of thatch, she watched winds, and snows, and rains, gorgeous sunsets, and successive moons at their full.
就在这间寝室里，就在茅屋再下几平方英尺的地方，她看见窗外没有尽头的凄风、苦雨、飞雪，看见无数的灿烂夕阳，看见一个又一个圆月。
Four hundred years ago, Galileo raised his homemade spyglass to the sky and spotted four of Jupiter's moons, revealing that other planets could have their own lunar companions.
400年前，伽利略将他自制的小望远镜对准星空，发现了木星的四颗卫星，我们这才知道其他行星也有自己的卫星。
The rings and moons, polluted and tinted though they may be now, therefore appear to preserve a record of their beginnings, frozen in time and space.
也许如今的光环和卫星已被污染，着色，尽管如此，但它们似乎仍然保留着冻结在时间与空间里的记录它们本源的证据。
If, as Olson predicts, humans reach Mars by the middle of this century, engineers and astronauts may then set their sights on the frozen planets, fiery moons and stars beyond.
如果就像Olson预言的那样，人类将在本世纪中叶踏上火星，那么工程师和宇航员就可能把目光投向那些更远的冰冻行星、炙热的卫星以及诸多恒星上。
Saturn's rings and moons are a diverse group, but some of their differences are only skin deep.
土星的光环和卫星都是一个多样化的群体，然而它们之间的区别也只有皮肤那么厚。
In their outward order from Jupiter, Jupiter's 4 major moons are Io, Europa, Ganymede and Callisto.
根据离木星的距离排列，木星的4颗卫星依次为：木卫一、木卫二、木卫三、木卫四。
Here, under her few square yards of thatch, she watched winds, snows, rains, gorgeous sunsets and successive moons at their full.
在这里，她整天呆在这几平方米大的茅草棚中，守着风风雨雨，望着雪花飘飘，目送灿烂的晚霞，数着一次又一次月圆。
She watched winds, and snows, and rains, gorgeous sunsets, and successive moons at their full.
她看著风风雨雨，霜晨雪夜，灿烂的夕阳，和由缺而圆的满月。
She watched winds, and snows, and rains, gorgeous sunsets, and successive moons at their full.
她看著风风雨雨，霜晨雪夜，灿烂的夕阳，和由缺而圆的满月。
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