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科学美国人60秒 SSS 2016-8-05

时间:2016-08-16 08:52:28

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(单词翻译)

Mars is a planet of outsized splendor1. Despite being only half as big and a tenth as heavy as Earth, it bears the solar system’s tallest mountain, longest canyon2 and largest crater3. At 22 and 12 kilometers wide, however, its inner moon Phobos and outer moon Deimos are figurative small potatoes. Scientists suspect both formed much as Earth’s single large moon did, from a massive debris4 disk ejected into orbit by a giant impact eons ago. But if Mars’s moons formed like Earth’s, why are they so very much smaller?

火星是一个拥有惊人光辉的行星。尽管它的体积只有地球的一半那么大,重量是地球的十分之一,但它拥有太阳系中最高的山峰、最长的峡谷以及规模最大的火山口,在22和12公里宽处,其内部卫星火卫一和火卫二像生动形象的两颗小土豆。科学家们怀疑这两个卫星的形成就像地球上形成独一无二的月球一样,在亿万年前,发生剧烈碰撞时,大量的碎片被送入轨道从而形成。但如果火星卫星的形成与月球的形成过程大体类似,为什么它们的体积如此之小?

The answer may be that they did not form alone. New simulations from Pascal Rosenblatt of the Royal Observatory5 of Belgium and colleagues show how the debris disk from a giant impact on Mars could have generated additional moons a few hundreds of kilometers in size. After forming in the dense6 inner regions of the disk, those larger moons would have stirred the disk’s sparser7 outer reaches, allowing smaller companions like Phobos and Deimos to coalesce8 from the ripples9. The study appears in the journal Nature Geoscience. [Rosenblatt et al, Accretion10 of Phobos and Deimos in an extended debris disc stirred by transient moons]

答案或许是它们并不是单独形成的。比利时皇家天文台的帕斯卡罗森布拉特和他的研究团队使用数值模拟了一次火星上的大碰撞事件,以及碰撞所造成的碎片盘演变,展示是如何形成其他的卫星,在几百公里之外。由于碎片的密集程度不同,较大的卫星会在碎片盘内侧吸积形成之后,其产生的引力牵引会搅动碎片盘的外侧,允许形小型卫星,如卫星火卫一和火卫二。这项研究发表在《自然地球科学》期刊上。

In this scenario11, the reason we only see Phobos and Deimos today is that the bigger moons were destroyed a few million years after their formation. Their low, fast orbits outpaced Mars’s rotation12, creating a tidal pull that sent them spiraling down to crash into the planet (Earth’s moon, by contrast, orbited slower than our planet’s rotation, allowing it to spiral outward and survive). Future investigations13 could test the new hypothesis by looking for clusters of Martian craters14 produced by the infalling moons, but in the meantime, proof that Mars can kill its companions is right before our eyes: The orbit of Deimos is stable, but Phobos is in a death spiral, losing 2 centimeters of altitude per year to Mars’s tidal pull. It will plunge15 into the planet in 20 to 40 million years, leaving lonely, far-out Deimos as the last vestige16 of what may have been a once-mighty system of Martian moons.

在这一假设下,我们今天之所以只看到火卫一和火卫二,是因为那些较大的卫星在它们形成几百万年后被摧毁。它们运行的低、快速轨道超过火星自转,汇成推动潮汐力使它们盘旋而下,撞上星球。(相比之下,地球上的卫星,环绕轨道运行的速度慢于地球自传。允许卫星像螺旋一样外传并生存下来。)未来的调查可以通过寻找由陨落的卫星所形成的火星陨石坑集群,来测试这一新假设。但与此同时,证明火星可以杀死它同伴的证据就在眼前:火卫二的运行轨道是稳定的,但火卫一处在“死亡螺旋”中,由于火星的潮汐力,每年高度降低2厘米。在未来二千至四千万年内,它将被拉向火星,孤独地陨落。非常遥远的火卫二,其最后的遗迹可能是一个曾经辉煌的火星卫星系统。


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1 splendor hriy0     
n.光彩;壮丽,华丽;显赫,辉煌
参考例句:
  • Never in his life had he gazed on such splendor.他生平从没有见过如此辉煌壮丽的场面。
  • All the splendor in the world is not worth a good friend.人世间所有的荣华富贵不如一个好朋友。
2 canyon 4TYya     
n.峡谷,溪谷
参考例句:
  • The Grand Canyon in the USA is 1900 metres deep.美国的大峡谷1900米深。
  • The canyon is famous for producing echoes.这个峡谷以回声而闻名。
3 crater WofzH     
n.火山口,弹坑
参考例句:
  • With a telescope you can see the huge crater of Ve-suvius.用望远镜你能看到巨大的维苏威火山口。
  • They came to the lip of a dead crater.他们来到了一个死火山口。
4 debris debris     
n.瓦砾堆,废墟,碎片
参考例句:
  • After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
  • Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上,导致蛀牙。
5 observatory hRgzP     
n.天文台,气象台,瞭望台,观测台
参考例句:
  • Guy's house was close to the observatory.盖伊的房子离天文台很近。
  • Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。
6 dense aONzX     
a.密集的,稠密的,浓密的;密度大的
参考例句:
  • The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
  • The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。
7 sparser d2f0ed212c015018ea678c104b0b1073     
adj.稀疏的,稀少的( sparse的比较级 )
参考例句:
8 coalesce oWhyj     
v.联合,结合,合并
参考例句:
  • And these rings of gas would then eventually coalesce and form the planets.这些气体环最后终于凝结形成行星。
  • They will probably collide again and again until they coalesce.他们可能会一次又一次地发生碰撞,直到他们合并。
9 ripples 10e54c54305aebf3deca20a1472f4b96     
逐渐扩散的感觉( ripple的名词复数 )
参考例句:
  • The moon danced on the ripples. 月亮在涟漪上舞动。
  • The sea leaves ripples on the sand. 海水在沙滩上留下了波痕。
10 accretion 5Jnyi     
n.自然的增长,增加物
参考例句:
  • Every culture is an accretion.每一种文化都是长期积淀的结果。
  • An accretion of sediment at the mouth of the river caused serious flooding.河口堆积物的增加导致河水严重泛滥。
11 scenario lZoxm     
n.剧本,脚本;概要
参考例句:
  • But the birth scenario is not completely accurate.然而分娩脚本并非完全准确的。
  • This is a totally different scenario.这是完全不同的剧本。
12 rotation LXmxE     
n.旋转;循环,轮流
参考例句:
  • Crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
  • The workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。
13 investigations 02de25420938593f7db7bd4052010b32     
(正式的)调查( investigation的名词复数 ); 侦查; 科学研究; 学术研究
参考例句:
  • His investigations were intensive and thorough but revealed nothing. 他进行了深入彻底的调查,但没有发现什么。
  • He often sent them out to make investigations. 他常常派他们出去作调查。
14 craters 1f8461e3895b38f51c992255a1c86823     
n.火山口( crater的名词复数 );弹坑等
参考例句:
  • Small meteorites have left impact craters all over the planet's surface. 这个行星的表面布满了小块陨石留下的撞击坑。 来自《简明英汉词典》
  • The battlefield was full of craters made by exploding shells. 战场上布满弹坑。 来自《现代英汉综合大词典》
15 plunge 228zO     
v.跳入,(使)投入,(使)陷入;猛冲
参考例句:
  • Test pool's water temperature before you plunge in.在你跳入之前你应该测试水温。
  • That would plunge them in the broil of the two countries.那将会使他们陷入这两国的争斗之中。
16 vestige 3LNzg     
n.痕迹,遗迹,残余
参考例句:
  • Some upright stones in wild places are the vestige of ancient religions.荒原上一些直立的石块是古老宗教的遗迹。
  • Every vestige has been swept away.一切痕迹都被一扫而光。

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