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
18
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] According to the passage, Mariner 10 was sent to observe Mercury because______.
选项
答案
little could be observed there
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3108819.html
相关试题推荐
________isthecenterofourplanetarysystemwasconsideredasheresybythech
PassageTwo[br]Whyisitdifficultforlow-incomefamiliestocookhealthymea
Thedifficultyofaproblemwasdefined________howlongittooktocomplete.A、by
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
HowcomeitissodifficulttofindEnglishfoodinEngland?InFranceyouea
随机试题
HowtoGuessYourAgeItseemstomethattheyareb
Whatistheman’sjob?[br][originaltext]W:WhyareyouleavingBurchester,Jo
下列选项中,属于防范恶意代码的加固方法的有()。A.安装系统安全补丁 B
A.≤15cfu/m B.≤10cfu/m C.≤5cfu/m D.≤0.
患者,男性,57岁,与家人发生争执,服药物中毒,急诊入院抢救。试验发现当酸化尿液
关于心电图各波段测量方法,错误的一项是A.时间的测量自波的开始部内侧量至波的终止
根据《中华人民共和国教师法》,学校或者其他教育机构对教师的考核内容不包括( )
股票投资收益率上升,最可能会给银行造成市场风险。( )
恒牙根尖发育完成的时间是A.萌出时 B.萌出后半年 C.萌出后1~2年 D
下列关于流动负债的相关表述,正确的有()。A.资产负债表日,企业应按合同利率计
最新回复
(
0
)