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  3. Since early times, people have been fascinated with the idea of life existing somewhere else besides earth. Until recently, scie

Since early times, people have been fascinated with the idea of life existing somewhere else besides earth. Until recently, scie

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问题     Since early times, people have been fascinated with the idea of life existing somewhere else besides earth. Until recently, scientists believed that life on other planets was just a【B1】______ dream. But now they are beginning to【B2】______places where life could form. In 1997, they saw evidence of planets near other stars like the sun. But scientists now think that life could be even nearer in our own【B3】______ system. One place scientists are studying very closely is Eu- ropa, a moon of Jupiter. Space probes have【B4】______ evidence that Europa has a large ocean under its surface. The probes have also made scientists think that under its surface Europa has a rocky core【B5】______ volcanic heat Water and heat from volcanic activity are two basic conditions needed for life to form. A third is certain basic chemicals such as carbon,【B6】______ and nitrogen. Scientists believe there might be such chemicals lying at the bottom of Eu- ropa’s ocean. They may have already created life, or may【B7】______. You may wonder if light is also needed for life to form. Until recently, scientists thought that light was【B8】______. But now, places have been found on earth that are in total blackness, such as caves several miles beneath the surface, and bacteria,【B9】______forms of life, have been seen there. So the lack of light in Europa’s subsurface ocean doesn’t automatically【B10】______ life forming.
【B4】
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