首页
登录
职称英语
Mercury, the planet nearest the sun, is difficult to observe from the Earth
Mercury, the planet nearest the sun, is difficult to observe from the Earth
游客
2023-10-18
32
管理
问题
Mercury, the planet nearest the sun, is difficult to observe from the Earth because it rises and sets within two hours of the sun. Consequently, little was known about the planet until the Mariner 10 spacecraft made several flybys in 1974 and 1975.
Planetary scientists can estimate the age of a planet’s surface by the number of impact craters on it. In general, the older the surface, the more crates it has. Some regions on Mercury are heavily cratered, suggesting that they are very old surfaces that were probably formed about 4 billion years ago. Between these regions are areas of gently rolling plains that may have been smoothed by volcanic lava flows or by accumulated deposits of fine material ejected during impacts. These plains are also old enough to have accumulated a large number of impact craters. Elsewhere on the planet are smooth, flat plains that are probably younger and volcanic in origin. These plains have relatively few impact craters. Sometime between the formation of the intercrater plains and the formation of the smooth plains, the whole planet may have shrunk as it cooled, causing the crust to buckle and form the long, steep cliffs called scarps.
The largest impact basin on Mercury has a diameter of about 800 miles and is surrounded by mountains that rise to heights of about 1.2 miles. The crater was probably created by the impact of a large planetesimal when Mercury was forming. On the opposite side of the planet is an area of hilly, linear terrain that probably resulted from seismic waves caused by the same impact.
Like other airless, solid bodies in the solar system, the entire surface of Mercury is covered with a layer of rubble called regolith, which is composed of material, ranging from dust to boulders, that was scattered when impact craters were formed. This debris was in turn broken up and redistributed by subsequent impacts.
Mercury is very dense and has a magnetic field that is about 1 percent as strong as the Earth’s. This suggests the existence of a planetary core composed of iron and nickel and constituting about 40 percent of the planet’s volume. The surface gravity is about one-third as strong as the Earth’s, and a thin atmosphere surrounds the planet. Radar images taken of Mercury in 1991 show what are considered to be large ice patches at the planet’s north pole.
Directions: Complete the following sentences with information given in the passage in a maximum of 10 words for each blank. [br] It is likely that the conditions on Mercury would______.
选项
答案
make life impossible
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3108818.html
相关试题推荐
________isthecenterofourplanetarysystemwasconsideredasheresybythech
Itwasfeltthathelackedthe________topursueadifficulttasktotheveryend
________toschoollifewaslessdifficultthanthepupilhadexpected.A、Adhering
PassageTwo[br]Whyisitdifficultforlow-incomefamiliestocookhealthymea
Inthefaceofunexpecteddifficulties,hedemonstratedatalentforquick,____
不管他怎样努力,他还是摆脱不了困难。——,hecouldn’tgetoutofdifficulty.Tryashemight(as有“虽然,尽管
Observeachildjanyonewilldo.【46】Youwillseethatnotadaypassesin
Observeachildjanyonewilldo.【46】Youwillseethatnotadaypassesin
HowcomeitissodifficulttofindEnglishfoodinEngland?InFranceyouea
HowcomeitissodifficulttofindEnglishfoodinEngland?InFranceyouea
随机试题
WhatwilltheclassdoonThursday?[br][originaltext]Iamcertainthatan
It’sclearthatsocialmedialikeTwitterandFacebookarechangingtheway
[originaltext]W:(1-1)So,Mike,youmanagetheinnovationprojectatCucinTech.
在美国10年期国债期货的交割,卖方可以使用()来进行交割。A、10年期国债B、大于10年期的国债C、小于10年期的国债D、任一符合芝加哥期货交易
OnenightinApril1912,ahugenew【B1】______liner,namedtheTitanic,was【B
WhenAppleshowedtheworldSiri,Ibelievetheyshowedusthenextmajor【C1
有个学生上课玩手机被老师批评,学生反驳范老师也上课玩手机。你怎么办?
用环氧乙烷消毒灭菌时,操作错误的是A.环氧乙烷应放在阴凉通风,无火源及明火处
在固定资产贷前调查报告中,有关银行业金融机构收益预测的内容主要有( )。A.利
患者男,35岁。温度计厂工人。主诉:易激动,易怒(示情感障碍),2年前有唇、手指
最新回复
(
0
)