Directions: Complete the following passage by using the words in the box. Each word can only be used once. Note that there is one word more than you need.
| A. recently B. forming C. locate D. primitive E. fascinated F. evidence G. volcanic H. chemicals I. created J. closely |
Since early times, people have been ___41___with the idea of life existing somewhere else besides earth. Until recently, scientists believe that life on other planets was just a hopeful dream. But now they are beginning to___42____places where life could form. In 1997, they saw ____43____of planets near other stars like the sun. But scientists now think that life could be even nearer in our own solar system. One place scientists are studying very closely is Europa, a moon of Jupiter. Space probes(探测器) have provided 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（核心） giving off____44____heat. Water and heat from volcanic activity are two basic conditions needed for life to form. A third is certain basic____45____such as carbon, oxygen and nitrogen. Scientists believe there might be such chemicals lying at the bottom of Europa’s ocean. They may have already____46____life or may be about to. You may wonder if light is also needed for life to form. Until____47____, scientists thought that light was essential. But now, places have been found on earth that are in total blackness such as caves several miles beneath the surface. And bacteria,___48____ forms of life, have been seen there. So the lack of light in Europa’s sub-surface ocean doesn’t automatically rule out life____49____.