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
外语
According to the best evidence gathered by space probes and astronomers, Mars is an inhospitable planet, more similar to Earth’s
According to the best evidence gathered by space probes and astronomers, Mars is an inhospitable planet, more similar to Earth’s
admin
2010-07-19
85
问题
According to the best evidence gathered by space probes and astronomers, Mars is an inhospitable planet, more similar to Earth’s Moon than to Earth itself a dry, stark, seemingly lifeless world. Mars’ air pressure is equal to Earth’s at an altitude of 100,000 feet. The air there is 95% carbon dioxide. Mars has no ozone layer to screen out the Sun’s lethal radiation. Daytime temperatures may reach above freezing, but because the planet is blanketed by the mere wisp of an atmosphere, the heat radiated back into space. Even at the equator, the temperature drops to -50℃ (-6(YF) at night. Today there is no liquid water, although valleys and channels on the surface show evidence of having been carved by running water. The polar ice caps are made of frozen water and carbon dioxide, and water may be frozen in the ground as permafrost.
Despite these difficult conditions, certain scientists believe that there is a possibility of transforming Mars into a more Earth-like planet. Nuclear reactors might be used to melt frozen gases and eventually build up the atmosphere. This in turn could create a "greenhouse effect" that would stop heat from radiating back into space. Liquid water could be thawed to form a polar ocean. Once enough ice has melted, suitable plants could be introduced to build up the level of oxygen in the atmosphere so that, in time, the planet would support animal life from Earth and even permanent human colonies. "This was once thought to be so far in the future as to be irrelevant," said Christopher McKay, a research scientist at the National Aeronautics and Space Administration. "But now it’s starting to look practical. We could begin work in four or five decades."
The idea of "terra-forming" Mars, as enthusiasts call it, has its roots in science fiction. But as researchers develop a more profound understanding of bow Earth’s ecology supports life, they have begun to see how it may be possible to create similar conditions on Mars. Don’t plan on homesteading on Mars any time soon, though. The process could take hundreds or even thousands of years to complete, and the cost would be staggering.
According to Christopher McKay, the possibility of transforming Mars______.
选项
A、could occur only in science fiction stories
B、will not begin for hundreds, even thousands, of years
C、is completely impractical
D、could be started in 40 to 50 years
答案
D
解析
转载请注明原文地址:https://kaotiyun.com/show/U8lO777K
0
专业英语八级
相关试题推荐
ThefollowingareallspecificmeasurestoguardagainstinjurieswiththeEXCEPTIONofInwhichparagraphdoestheauthorstat
Inmodernsociety,mostpeopleseemtobelievethatthesocietyisfullofcompetition.Inordertobesuccessful,everyonehas
______isgenerallydefinedasthestudyofmeaningandusuallypaysattentiontothestudyofmeaningoflinguisticunitsthems
WhichofthefollowingstatementsabouttheAmericanDefenseDepartmentisTRUE?
Whatdidthegovernmentintendtodointhebeginning?
RabbiMichaelStrassfeldsaysthatoneshouldbegrateful______.
Thepassageismainlyconcernedwith______.AnnaTibaijuka(Para.5)andMichaelMutter(para.7)seemtodifferover______.
AccordingtoMr.Verleger,whatisthemostimportantchangeintheglobalenergyeconomyin30years?
TheUnitedNationsConferenceonDrugAbusethattookplaceearlierthisyearinVienna,wasaveryproductivemeeting.Asnever
1 Duringtheadolescence,thedevelopmentofpoliticalideologybecomesapparentintheindividual;ideologyhereisdefinedas
随机试题
简述见索即付保证的概念和特点。
解决方案分析的步骤有
在单因素方差分析中,以下正确的一项是
男,20岁。3年前无明显诱因渐起孤僻少语,不愿参加集体活动,甚至与父母也很少交流,上课时注意力不集中,成绩下降。个人生活懒于料理。该患者最适宜做的检查是()
依据《建设工程质量管理条例》规定,在实行监理的工程,项目监理机构要对( )进行约束和协调,以使建设主体各尽其责。
借款人不能按期归还贷款时,应当在贷款到期日之前,向银行申请()。
根据我国监管当局要求,商业银行并表和未并表的杠杆率均不得低于()。
某夜,丁某埋伏在路边准备进行抢劫,后发现来人是本单位同事,遂收起匕首,与同事打完招呼后回家睡觉,丁某的行为是()。
Themostobviouspurposeofadvertisingistoinformtheconsumerofavailableproductsorservices.Thesecond【C1】______istos
Notalldecisionsarealike.Noriseverydecisionmadeinthesamemanner.Althoughsomeactionsyouundertakederivetheirbas
最新回复
(
0
)