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托福阅读材料推荐:距离土星第七远的土星卫星

2016-07-18 15:36:25来源：网络

　　本文是托福听力/阅读背景知识拓展：Excitement Builds for the Possibility of Life on Enceladus(距离土星第七远的土星卫星)。托福阅读材料推荐:距离土星第七远的土星卫星是很好的托福阅读背景知识补充阅读材料。希望对大家托福备考有所帮助。更多精彩尽请关注新东方在线托福网!

Excitement Builds for the Possibility of Life on Enceladus

Scientists tackle the question of how to search for life on Saturn’s sixth-largest moon

　　By Annie Sneed on June 28, 2016

　　Saturn's icy moon Enceladus is thought to host a liquid ocean beneath its frozen surface that could be hospitable to life. Credit: NASA

　　Saturn’s frozen moon Enceladus is a tantalizing world—many scientists are increasingly convinced it may be the best place in our solar system to search for life. NASA’s Cassini spacecraft, currently orbiting Saturn, has made intriguing observations of icy jets spewing from a suspected underground liquid ocean on the mysterious world that might be hospitable to alien life.

　　Cassini’s tour is due to wind down in 2017, and scientists badly want to send a dedicated mission to Enceladus to look for signs of life. In fact, some have already started seriously thinking about exactly how they might do this—including planetary scientist Carolyn Porco, who is the imaging team leader for Cassini. Earlier this month, she gathered a group of researchers including oceanographers, organic chemists and astrobiologists at the University of California, Berkeley, to strategize how to search for extraterrestrials on Enceladus—which, according to Porco, “is a total bitch of a problem to solve.”

　　Although Enceladus is small in size and shrouded in a thick shell of ice, it appears to be a habitable world: It has a source of energy from friction created by its orbit around Saturn, organic compounds that are building blocks for life and a liquid water ocean underneath all that ice. But just because Enceladus may be hospitable to life does not mean life exists there; it will take much more work to definitively prove it. At the Berkeley meeting, scientists laid out the data Cassini has collected for Enceladus—they discussed analyses of its geysers, measurements of its ice shell, ideas on what its ocean chemistry might be like, and more. Yet even with all the newest data and models scientists have, they are not even close to detecting organisms on Enceladus—hence the need for a space mission.

　　Finding life there would be a profound revelation that we are not alone in the cosmos. Furthermore, the discovery of organisms—or the lack thereof—could answer the subtler mystery of how life started on Earth. Researchers at the meeting presented two major opposing theories about how life here originated (in the ocean versus on land), and the group discussed how exploring Enceladus would inform this debate. “It would be a test of one of the ideas about the origin of life,” Porco says—specifically, the proposition that Earth’s species sprang in the sea. For example, if organisms exist in Enceladus’s ocean and presumably arose there, it would support the theory that life began on Earth in hydrothermal vents (hot, nutrient-rich, deep-sea vents on the ocean floor) rather than in patches of water on land.

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