火星卫星火卫一正在缓慢瓦解-凯发k8官网

火星卫星火卫一正在缓慢瓦解
文章来源:未知 文章作者:enread 发布时间:2015-11-13 05:37 字体: [ ] 
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the long, shallow 1 2 the surface of phobos are likely early signs of the 3 failure that will ultimately destroy this moon of mars. orbiting a 4 3,700 miles (6,000 kilometers) above the surface of mars, phobos is closer to its planet than any other moon in the solar system. mars' gravity is drawing in phobos, the larger of its two moons, by about 6.6 feet (2 meters) every hundred years. scientists expect the moon to be pulled apart in 30 to 50 million years.
 
"we think that phobos has already started to fail, and the first sign of this failure is the production of these grooves," said terry hurford of nasa's goddard space flight center in greenbelt, maryland.
 
the findings by hurford and his colleagues are being presented nov. 10, 2015, at the annual meeting of the division of planetary sciences of the american 5 society at national harbor, maryland.
 
phobos' grooves were long thought to be fractures caused by the impact that formed stickney 6. that collision was so powerful, it came close to shattering phobos. however, scientists eventually 7 that the grooves don't radiate outward from the crater itself but from a focal point nearby.
 
more recently, researchers have proposed that the grooves may instead be produced by many smaller impacts of material ejected from mars. but new modeling by hurford and colleagues supports the view that the grooves are more like "stretch marks" that occur when phobos gets 8 by tidal forces.
 
the gravitational pull between mars and phobos produces these tidal forces. earth and our moon pull on each other in the same way, producing tides in the oceans and making both planet and moon slightly egg-shaped rather than 9 round.
 
the same explanation was proposed for the grooves decades ago, after the viking spacecraft sent images of phobos to earth. at the time, however, phobos was thought to be more-or-less solid all the way through. when the tidal forces were calculated, the stresses were too weak to fracture a solid moon of that size.


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1 e2ee808c594bc87414652e71d74585a3     
n.沟( groove的名词复数 );槽;老一套;(某种)音乐节奏v.沟( groove的第三人称单数 );槽;老一套;(某种)音乐节奏
参考例句:
  • wheels leave grooves in a dirt road. 车轮在泥路上留下了凹痕。 来自《简明英汉词典》
  • sliding doors move in grooves. 滑动门在槽沟中移动。 来自《现代汉英综合大词典》
2 kpgzto     
n.衬里,衬料
参考例句:
  • the lining of my coat is torn.我的外套衬里破了。
  • moss makes an attractive lining to wire baskets.用苔藓垫在铁丝篮里很漂亮。
3 itxw5     
adj.构造的,组织的,建筑(用)的
参考例句:
  • the storm caused no structural damage.风暴没有造成建筑结构方面的破坏。
  • the north american continent is made up of three great structural entities.北美大陆是由三个构造单元组成的。
4 rc1xe     
adj.纯粹的;仅仅,只不过
参考例句:
  • that is a mere repetition of what you said before.那不过是重复了你以前讲的话。
  • it's a mere waste of time waiting any longer.再等下去纯粹是浪费时间。
5 ketyo     
adj.天文学的,(数字)极大的
参考例句:
  • he was an expert on ancient chinese astronomical literature.他是研究中国古代天文学文献的专家。
  • houses in the village are selling for astronomical prices.乡村的房价正在飙升。
6 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。
7 duszmp     
adj.坚定的;有决心的
参考例句:
  • i have determined on going to tibet after graduation.我已决定毕业后去西藏。
  • he determined to view the rooms behind the office.他决定查看一下办公室后面的房间。
8 iutzwv     
adj.畸形的;变形的;丑的,破相了的
参考例句:
  • he was born with a deformed right leg.他出生时右腿畸形。
  • his body was deformed by leprosy.他的身体因为麻风病变形了。
9 8mzxb     
adv.完美地,无可非议地,彻底地
参考例句:
  • the witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
  • everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。
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