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Since early times, people have been fascinated with the idea of life existing somewhere else besides earth.
很早的時候人們就開始對地球之外的生命充滿著遐想。
Until recently, scientists believed that life on other planets was just a hopeful dream.
直到最近，科學家還相信外星生命只是一個美好的愿景。
But now they are beginning to locate places where life could form.
但是現在，他們已經開始在地球之外發現可能孕育生命的地方了。
In 1997, they saw evidence of planets near other stars like the sun.
1997年，他們找到證據證明與太陽類似恒星附近有行星的存在。
But scientists now think that life could be even nearer in our own solar system.
他們現在甚至認為我們的太陽系就可能有外星生命。
One place scientists are studying very closely is Europa, a moon of Jupiter.
他們正在密切觀察的對象之一是歐羅巴，木星的衛星。
Space probes have provided evidence that Europa has a large ocean under its surface.
航天探測器探測數據證明木衛二表層之下蘊藏著一片汪洋大海。
The probes have also made scientists think that under its surface Europa has a rocky core giving off volcanic heat.
科學家們還相信木衛二的巖心是不斷散發著熱量的火山熱源。
Water and heat from volcanic activity are two basic conditions needed for life to form.
水和火山活動散發的熱量是生命存在的兩個基本前提。
A third is certain basic chemicals such as carbon, oxygen and nitrogen.
第三個必要條件是化學成分，如：碳、氧、氮。
Scientists believe there might be such chemicals lying at the bottom of Europa's ocean.
科學家認為木衛二地表下的海床上一定存在這些化學物質。
They may have already created life, or may be about to.
它們可能已經孕育了生命。
You may wonder if light is also needed for life to form.
你可能會想陽光是不是生命形成的必要條件。
Until recently, scientists thought that light was essential.
科學家最近對此得出肯定的結論。
But now, places have been found on earth that are in total blackness, such as caves several miles beneath the surface, and bacteria, primitive forms of life, have been seen there.
但是現在人們在地球上一些完全暗無天日的地方也發現了細菌等原始的生命形式，比如地面幾英里以下的洞穴中。
So the lack of light in Europa's subsurface ocean doesn't automatically rule out life forming.
因此，并不能僅僅因為木衛二地下海洋缺乏陽光就排除其孕育生命的可能。
Questions 16 to 18 are based on the passage you have just heard.
請根據剛剛聽到的內容回答16-18題。
Question 16. What did scientists once believe according to the passage?
問題16：科學家過去的想法是怎樣的？
Question 17. What have scientists found about Europa, a moon of Jupiter?
問題17：關于木星的衛星木衛二科學家們有什么發現？
Question 18. What scientists come to know recently about the formation of life?
問題18：科學家最近對生命的形成有什么新的認識？
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