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  3. Astronomers who study planet formation once believed that comets—because the

Astronomers who study planet formation once believed that comets—because the

游客2024-01-10  45
问题     Astronomers who study planet formation once believed that comets—because they remain mostly in the distant Oort cloud, where temperatures are close to absolute zero—must be pristine relics of the material that formed the outer planets. The conceptual shift away from seeing comets as pristine relics began in the 1970s, when laboratory simulations revealed there was sufficient ultraviolet radiation reaching comets to darken their surfaces and there were sufficient cosmic rays to alter chemical bonds or even molecular structure near the surface. Nevertheless, astronomers still believed that when a comet approached the Sun—where they could study it—the Sun’s intense heat would remove the corrupted surface layer, exposing the interior. About the same time, though, scientists realized comets might contain decaying radioactive isotopes that could have warmed cometary interiors to temperatures that caused the interiors to evolve. [br] It  can  be  inferred  that  the  author  would  agree  with  which  of  the  following  statements  about  the  "laboratory simulations"?
选项 A、The simulations showed that despite the low temperatures in the Oort cloud, there was sufficient energy there to alter the comet.
B、Astronomers were initially reluctant to accept what the simulation showed about the composition of comets.
C、The simulations themselves did not eliminate the possibility that comets contain pristine relics of material from the early solar system.
答案 A,C
解析 第二句的实验想要表明的是：即使奥尔特星云是绝对零度，紫外射线等依然可以让彗星不纯，因此选项A正确。C项第二句只能表明彗星的表面不纯，但是内部依然有可能是纯的，因此选项C正确。B项第三句天文学家其实承认了第二句彗星不纯的理由。
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