Europa is the smallest of planet Jupiter’s four largest moons and the second moon out from Jupiter. Until 1979, it was just another astronomy textbook statistic. Then came the close-up images obtained by the exploratory spacecraft Voyager 2, and within days, Europa was transformed-in our perception, at least-into one of the solar system’s most intriguing worlds. The biggest initial surprise was the almost total lack of detail,
especially from far away. Even at close range, the only visible features are thin, kinked brown lines resembling cracks in an eggshell. And this analogy is not far off the mark.
The surface of Europa is almost pure water ice, but a nearly complete absence of craters indicates that Europa’s surface ice resembles Earth’s Antarctic ice cap. The eggshell analogy may be quite accurate since the ice could be as little as a few kilometers thick –a true shell around what is likely a subsurface liquid ocean that , in turn, encases a rocky core. The interior of Europa has been kept warm over the eons by tidal forces generated by the varying gravitational tugs of the other big moons as they wheel around Jupiter. The tides on Europa pull and relax in an endless cycle. The resulting internal heat keeps what would otherwise be ice melted almost to the surface. The cracklike marks on Europa’s icy face appear to be fractures where water or slush oozes from below.
Soon after Voyager 2’s encounter with Jupiter in 1979, when the best images of Europa were obtained, researchers advanced the startling idea that Europa’s subsurface ocean might harbor life. Life processes could have begun when Jupiter was releasing a vast store of internal heat. Jupiter’s early heat was produced by the compression of the material forming the giant planet. Just as the Sun is far less radiant today than the primal Sun, so the internal heat generated by Jupiter is minor compared to its former intensity. During this warm phase, some 4.6 billion years ago, Europa’s ocean may have been liquid right to the surface, making it a crucible for life.
1. What does the passage mainly discuss?
(A) The effect of the tides on Europa’s interior
(B) Temperature variations on Jupiter’s moons
(C) Discoveries leading to a theory about one of Jupiter’s moons
(D) Techniques used by Voyager 2 to obtain close-up images.
答案有C跟D,我是選C
4. It can be inferred from the passage that astronomy textbooks prior to 1979
(A) provided many contradictory statistics about Europa
(B) considered Europa the most important of Jupiter’s moons
(C) did not emphasize Europa because little information of interest was available
(D) did nor mention Europa because it had not yet been discovered
答案有A跟C,我是選C
6. It can be inferred from the passage that Europa and Antarctica have in common which of the following?
(A) Both appear to have a surface with many craters.
(B) Both may have water beneath a thin, hard surface.
(C) Both have an ice can that is melting rapidly.
(D) Both have areas encased by a rocky exterior.
答案有B跟C,我是選C
9 According to the passage, what is believed to cause the thin lines seen on Europa’s surface?
(A) A long period of extremely high tides
(B) Water breaking through from beneath the surface ice
(C) The continuous pressure of slush on top of the ice
(D) Heat generated by the hot rocky core
這題只有在03年10月出,答案是B
麻煩各位大大了,感激不盡