ThankslargelytotheKeplerspacetelescope,astronomershaved...

问题详情：

Thanks largely to the Kepler space telescope, astronomers have discovered more than 2,000 planets in the universe. Kepler’s final goal is to find worlds similar to Earth-places where there’s a chance that alien life might exist.

But the search for life will still not be easy. It will be important to choose the best possible targets. That’s the reasoning behind two new rating systems (评估体系)proposed by Washington State University environmental scientist Dirk Schulze-Makuch, along with nine other colleagues.

The first rating system is called the Earth Similarity Index, or ESI. That’s just what it sounds like: it’s a measure of how closely an alien world matches Earth in terms of size and temperature. The temperature is important because liquid water is an important part for life.

The size of the planet seems important too. If a planet is too small, like Mars, it might not have enough gravity (引力) to hold on to its atmosphere. If the planet is too big, gravity might have pulled in too much atmosphere, which would create too much pressure at the surface. A world four or five times as large as Earth might be able to support life. But anything bigger than that could cause problems.

This second system is called the Planetary Habitability Index, or PHI. It includes planets that have a solid surface of some kind, protected by an atmosphere of some kind. Other things necessary under the PHI system are some sort of energy source (sunlight); some sort of chemical environment that allows the formation of complex molecules (分子); and the presence of liquid-but not necessarily water.

The search will get easier as technology improves. Still, these new ways of looking for alien life give us our best chance of learning if somewhere out we have galactic (银河的)relatives.

66. Kepler is         .

   A. a scientist          B. an organization         C. a system         D. a telescope

67. According to the 5th paragraph, to support life, the following are necessary EXCEPT         .

   A. a solid surface       B. water      C. a protective atmosphere      D. an energy source

68. Why is there no life in Mars?

   A. Because the Mars is too hot to keep the water.   B. Because the sun is far away from the Mars.

  C. Because the Mars can’t keep the atmosphere.  D. Because there is not any other energy in Mars.

69. We can infer that the text is         .

   A. a description of natural resources        B. a research report    

  C. a book review                       D. an introduction to space science 

70. What does the text mainly talk about?

   A. New ways to look for alien life.            B. Goals to find worlds similar to Earth.

  C. Systems to search for more planets.         D. Reports made by Dirk Schulze-Makuch.

【回答】

   DBCDA

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