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  3. The untrained eye might have trouble distinguishing the latest images from Mercury—released last week at a NASA press conference

The untrained eye might have trouble distinguishing the latest images from Mercury—released last week at a NASA press conference

admin2015-03-25  29
问题     The untrained eye might have trouble distinguishing the latest images from Mercury—released last week at a NASA press conference here—from countless images of Earth’s moon, but don’t tell that to Sean Solomon. Mercury "was not the place we expected," says Solomon, principal investigator of the MESSENGER mission to Mercury. "It was not the moon. " The first close look at the innermost planet in 33 years and the first look ever at one-third of it revealed a new side to the innermost planet: much more volcanism than seen before, deeply excavating impact craters, and—unique in the solar system—"The Spider. "
    The Mariner 10 spacecraft last flew by Mercury in 1975, returning images suggesting that lava once flowed across the surface, at least in places. But volcanism "wasn’t accepted by everyone ," says imaging team member Louise Prockter of Johns Hopkins University’s Applied Physics Laboratory in Laurel, Maryland. Now, "there’s very little doubt there has been widespread volcanic resurfacing of Mercury. " She pointed to impact craters hundreds of kilometers across with floors so smooth that they must have been partially filled by lava. Team member Robert Strom of the University of Arizona, Tucson, also found that the side of Mercury seen by Mariner 10 turns out to be more heavily cratered by impacts than the side seen for the first time by MESSENGER. That means that lava has flooded the MESSENGER side even more extensively than the other side. "There’s been a lot of volcanic activity on Mercury," says Strom.
    The moon has its volcanic flooding, too—witness the dark "scars," or maria, that shape the man(or woman)in the moon—but MESSENGER found a mercurial variation on such light-dark patterning. Caloris is a huge-1550-kilometer-wide-impact basin glimpsed by Mariner 10 but now seen in its entirety by MESSENGER. On the moon, such giant impact basins were often filled with dark lava to form maria, but Caloris has the opposite pattern. Its interior is lighter and is surrounded by a darker ring. Perhaps the Caloris impact excavated deep, lighter-colored rock and left it at the surface without flooding it with lava, says Solomon, director of the Carnegie Institution of Washington’s Department of Terrestrial Magnetism in Washington, D. C. Including smaller craters with distinctive dark rims, "we’ve got a variety of natural drill holes into Mercury’s interior," says Solomon.
    Then there’s The Spider more than 50 troughs radiate from near the center of Caloris where a 40-kilometer-wide crater has formed. Whether the crater has anything to do with the radiating troughs, Prockter can’t say; no one has ever seen anything like The Spider. One possibility is that the formation of Caloris somehow created a plume of molten rock that rose beneath the basin’s center, bulging the basin floor upward and cracking the crust to form the troughs. The crater would then have been an accidental impact. MESSENGER returns in October for another look at Mercury on its way to entering orbit in 2011.
We can learn from the fourth paragraph that
选项 A、Prockter knows the relation between the crater and the radiating troughs.
B、the Spider is a unique phenomenon in the solar system.
C、the Spider is formed by the lava in Caloris.
D、another investigation will be done by Mariner 10 in the year 2011.
答案B
解析 推理判断题。根据题干提示定位至第四段，本段讨论的是水星的一种奇怪地形。该段第二句说Whether the crater has anything to do with the radiating troughs，Prockter can’t say。故[A]错误；同样，根据no one has ever seen anything like The Spider一句，可知[B]正确；[C]对The Spider形成原因的描述有误；2011年探测水星的是MESSENGER而不是Mariner10，故[D]错误。
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