首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
For more than thirty years after astronauts first set foot on the Moon, scientists have been unable to unravel the mystery of wh
For more than thirty years after astronauts first set foot on the Moon, scientists have been unable to unravel the mystery of wh
admin
2010-01-13
57
问题
For more than thirty years after astronauts first set foot on the Moon, scientists have been unable to unravel the mystery of where the Earth’s only satellite came from. But now there is direct evidence that the Moon was born after a giant collision between the young Earth and another planet.
Previous studies of rocks from the Earth and the Moon have been unable to distinguish between the two, suggesting that they formed from the same material. But this still left room for a number of theories explaining how—for example, that the Moon and Earth formed from the same material at the same time. It was even suggested that the early Earth spun so fast it formed a bulge that eventually broke off to form the Moon.
Franck Poitrasson, and his colleagues at the Swiss Federal Institute of Technology have compared Moon rocks with rocks from Earth and discovered a surprising difference. They analysed the weight of the elements present in the rock using a highly accurate form of mass spectroscopy(光谱研究) that involves vaporising a sample by passing it through an argon (氩) flame. Although they appeared very similar in most respects, the Moon rocks had a higher ratio of iron-57 to iron-54 isotopes(同位素)than the Earth rocks. "The only way we could explain this difference is that the Moon and the Earth were partly vaporised during their formation," says Poitrasson.
Only the popular "giant planetary impact" theory could generate the temperatures of more than 1700℃ needed to vaporise iron. In this scenario, a Mars-sized planet known as Theia crashed into Earth 50 million years after the birth of the Solar System. This catastrophic collision would have released 100 million times more energy than the impact believed to have wiped out the dinosaurs—enough to melt and vaporise a large portion of the Earth and completely destroy Theia. The debris from the collision would have been thrown into orbit around the Earth and eventually coalesced to form the Moon.
When iron is vaporised, the lighter isotopes burn off first. And since the ejected debris that became the Moon would have been more thoroughly vaporised, it would have lost a greater proportion of its lighter iron isotopes than Earth did. This would explain the different ratios that Poitrasson has found.
Previous studies could not distinguish between ______.
选项
A、the rocks from the Earth and the Moon
B、the Earth and the Moon
C、the Moon and the man-made satellites
D、the young Earth and other planets
答案
A
解析
本题是具体细节题。解题的关键是要理解第2段第1句中unable to distinguish between the two这部分the two指的是什么,分析句子结构可以看出the two指的是该句前半部分提到的rocks from the Earth and (rocks from) the Moon.
转载请注明原文地址:https://kaotiyun.com/show/Vimi777K
0
在职申硕(同等学力)英语
相关试题推荐
Formillionsofyearsbeforetheappearanceoftheelectriclight,shiftwork,all-nightcableTVandtheInternet,theEarth’s
Therearehiddenfactorswhichscientistscall"feedbackmechanisms".Nooneknowsquitehowtheywillinteractwiththechangin
Therearehiddenfactorswhichscientistscall"feedbackmechanisms".Nooneknowsquitehowtheywillinteractwiththechangin
EvenbeforeHistorianJosephEllisbecameabest-sellingauthor,hewasfamousforhisvividlectures.Inhispopularcoursesat
Tocontrol(quality)and(making)decisions(about)productionareamongthemanyresponsibilitiesofan(industrial)engineer.
Whatproducesawaterproofsuperglue,actslikeavacuumcleaner,andeventeachesscientistsaboutgenerepair?Thehumblelit
A:I’manxioustogetstartedonmyproject.Canwediscussitsometimebeforetheweekend?B:______
Whatismostremarkableabouttheproposalmadebythetwoscientists?Ifwhatisproposedbythetwoscientistsbecomestrue,
Whatismostremarkableabouttheproposalmadebythetwoscientists?Whatisthebiggestproblemwithhydrogen-poweredcars?
Hehastroubleunderstandingthatotherpeoplejudgehimbyhissocialskillsandconduct.
随机试题
男孩,10个月。1周来发热、咳嗽伴腹泻、呕吐,每天10余次,伴有嗜睡,继而出现全身性惊厥4次,每次历时1~2min,神志不清。检查:患儿呈昏迷状态,颈软,四肢活动对称,心、肺无异常,肝肋下3.5cm,质中韧感。查血白细胞数12.0×109/L,中性粒细胞0
甲县工商局对汤山纺织厂作山罚款200万元的处罚决定,并且立即执行。汤山纺织厂向市工商局申请复议,市工商局维持了处罚决定,纺织厂随后向法院提起诉讼,一审法院判决维持该处罚决定。原审裁判遗漏了必须参加诉讼的当事人或诉讼请求的,二审法院应如何处理?___
护理目标陈述包括()
头痛牵引项背多属
下列关于使用手持电动工具和移动式电气设备的说法中,错误的是()。
某地方建设行政管理部门于2007年5月10日针对某建筑公司恶意拖欠劳务费用下发了给予其一年内禁止在本区域内参加投标的处罚决定,建筑公司于2007年5月15日收到该处罚通知,建筑公司对此不服的话最迟应于()前提起行政复议。
某公园要在园内东、南、西、北四个区域种植四种不同的特色树木,每个区域只种植一种。选定的特色树种为:北松、银杏、乌桕和龙柏。布局和基本要求是:(1)如果在东区或者南区种植银杏,那么在北区不能种植龙柏或乌桕。(2)北区或东区要种植北松或者银
2013~2015年,试验发展经费支出年平均增加:
ItisobviouslynecessarythatboththePresidentandhisadvisers______downtoearth.
Itisabadlawandshouldbe____________(取消)atonce.
最新回复
(
0
)