- UID
- 1335328
- 在线时间
- 小时
- 注册时间
- 2018-3-26
- 最后登录
- 1970-1-1
- 主题
- 帖子
- 性别
- 保密
|
Io and Europa, the inner two of Jupiter's four largest moons, are about the size of Earth`s moon and are composed mostly or entirely of rock and metal. Ganymede and Callisto are larger and roughly half ice. Thus, these four moons are somewhat analogous to the planets of the solar system, in which the rock- and metal-rich inner planets are distinct from the much larger gas- and ice-rich outer planets. Jupiter's moons are, however, more "systematic" :many of their properties vary continuously with distance from Jupiter. For example, lo is ice-free, Europa has a surface shell of ice, and while Ganymede and Callisto are both ice-rich, outermost Callisto has more.
This compositional gradient has geological parallels. lo is extremely geologically active, Europa seems to be active on a more modest scale, and Ganymede has undergone bouts of activity in its geological past. Only Callisto reveals no geological activity. In similar fashion, Callisto's surface is very heavily cratered from the impact of comets and asteroids; Ganymede, like Earth`s moon, is heavily cratered in parts; Europa is very lightly cratered; and no craters have been detected on lo, even though Jupiter's gravity attracts comets and asteroids passing near it, substantially increasing the bombardment rate of the inner moons compared to that of the outer ones. But because of lo's high degree of geological activity, its surface undergoes more-or-less continuous volcanic resurfacing.
请教一下各位！这篇文章题目都会做，就是第二段主题句This compositional gradient has geological parallels.不是很懂。如果大家没时间看文章我大概说一下内容，第一段描述了4个卫星并且提出它与太阳系有相似性，而且它们比太阳系更加“systematic”，然后举了一些systematic的例子，这些例子体现了它们的compositional gradient。
OG说第二段的内容是further证明systematic的，我的问题是：第二段的主题句里面的parallel是取什么意思？是平行还是相似处？从这句话怎么看出第二段是要继续讲systematic的？
谢谢！ |
|
京公网安备11010202008513号 京ICP证101109号 京ICP备12012021号
发表于 2018-5-19 10:57:44
收藏
收藏
楼主