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
24
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] Large ice patches were observed on Mercury’s north pole, which suggests that______
选项
答案
the north pole faces away from the sun
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3108820.html
相关试题推荐
________isthecenterofourplanetarysystemwasconsideredasheresybythech
Itwasfeltthathelackedthe________topursueadifficulttasktotheveryend
PassageTwo[br]Whyisitdifficultforlow-incomefamiliestocookhealthymea
Thepolicehaddifficultyin________thefansfromrushingontothestagetotake
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
Youhavetoreadthemanualcarefullyfirst,otherwiseyou______havedifficulty
______yourhelp,they’dneverhavebeenabletoovercomethedifficulties.A、Were
Youhavetoreadthemanualcarefullyfirst,otherwiseyou______havedifficulty
随机试题
SportsManyanimalsengageinp
在中唐时期的诗人中,为晚唐唯美主义诗风先导的诗人是()A.柳宗元 B.白居易
关于股权投资基金信息披露,说法错误的是()。A、投资者可以登录中国证券业协会指
粉末中分支状石细胞甚多的药材是A.红花B.辛夷C.西红花D.丁香E.洋金花
麻黄粉末中可见气孔为()。A.不定式B.不等式C.环式D.直轴式E.气孔特异内
下列叙述正确反映元大都城市规划与建设特点的是( )。A.重视对自然地理形态的利
根据《建筑灭火器配置验收及检査规范》(GB50444-2008)的规定,下列灭
患者,女,58岁,缺失,余牙正常、均稳固,舌系带至牙龈距离为l0mm,下颌舌侧牙
有限责任公司设监事会,其成员不得少于()人。A.2 B.3 C.5 D.1
关于现浇钢筋混凝土板式楼梯,下列说法正确的有()。 A.梯段底面平整,外形简
最新回复
(
0
)