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
17
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] The layer of rubble covering Mercury is called______.
选项
答案
regolith
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3108817.html
相关试题推荐
Itwasfeltthathelackedthe________topursueadifficulttasktotheveryend
Thepolicehaddifficultyin________thefansfromrushingontothestagetotake
Thedifficultyofaproblemwasdefined________howlongittooktocomplete.A、by
______herphonenumber,wehadsomedifficulty______her.A、Notknowing;contactin
Observeachildjanyonewilldo.【46】Youwillseethatnotadaypassesin
Observeachildjanyonewilldo.【46】Youwillseethatnotadaypassesin
Observeachildjanyonewilldo.【46】Youwillseethatnotadaypassesin
Observeachildjanyonewilldo.【46】Youwillseethatnotadaypassesin
______yourhelp,they’dneverhavebeenabletoovercomethedifficulties.A、Were
HowcomeitissodifficulttofindEnglishfoodinEngland?InFranceyouea
随机试题
WhenyoumeetJohnthisafternoon,don’tforget(tell)________himaboutourcas
Intheworldofentertainment,TVtalkshowshaveundoubtedlyfloodedevery
错图中对向来车越线占道行驶,遇到这种情况要减速慢行,必要时停车,不能向左占道行驶。
互易二端口网络满足()。
按人们对教育法律现象的认识分,教育法律意识分为:()A.教育法律心理
下列有关大椎穴主治病证的叙述,不正确的是A.热病、疟疾 B.风疹、痤疮 C.
陈老师在教学时引用徐霞客的诗句“五岳归来不看山,黄山归来不看岳”,有学生产生了疑
下列物质中,两个氢原子的化学性质不同的是()。 A.乙炔B.甲酸C.甲醛
患者背部红肿,多个脓点,有波动感,糖尿病病史( )。A.疖 B.痈 C.丹
在职业健康安全管理体系与环境管理体系的维持过程中,组织对其自身的管理体系所进行的
最新回复
(
0
)