标题: 求鉴定，是否GWD答案有误GWD17-Q35 to Q37 [打印本页] 作者: ran2010zx 时间: 2011-4-10 18:26 标题: 求鉴定，是否GWD答案有误GWD17-Q35 to Q37 GWD17-Q35to Q37: (Thispassage was excerpted from material published in 1996.) When a large body strikes a planet ormoon, material is ejected, thereby creating a hole in the planet and a local deficitof mass. This deficit shows up as agravity anomaly: the removal of thematerial that has been ejected to make the hole results in an area of slightlylower gravity than surrounding areas. One would therefore expect that all of the large multi-ring impactbasins on the surface of Earth’s Moon would show such negative gravityanomalies, since they are, essentially, large holes in the lunar surface. Yet data collected in 1994 by the Clementinespacecraft show that many of these lunar basins have no anomalously low gravityand some even have anomalously high gravity. Scientists speculatethat early in lunar history, when large impactors struck the Moon’s surface,causing millions of cubic kilometers of crustal debris to be ejected, densermaterial from the Moon’s mantle rose up beneath the impactors almost immediately,compensating for the ejected material and thus leaving no low gravity anomalyin the resulting basin. Later, however,as the Moon grew cooler and less elastic, rebound from large impactors wouldhave been only partial and incomplete. Thus today such gravitationalcompensation probably would not occur: the outer layer of the Moon is too cold and stiff. 36. Q36: Thepassage suggests that if the scientists mentioned in line 19 are correct intheir speculations, the large multi-ring impact basins on the Moon with themost significant negative gravity anomalies probably
A. were not formed early in the Moon’s history B. were not formed by the massive ejection ofcrustal debris C. are closely surrounded by other impactbasins with anomalously low gravity D. were created by the impact of multiple largeimpactors E. were formed when the Moon was relativelyelastic