Scientists say there are more than three hundred thousand small objects or pieces of debris (碎片) that are larger than one centimeter in orbit round the earth. Any one of these could cause damage to a spacecraft. This is because orbital debris travels very fast― about thirtytwo thou?sand kilometers an hour or more. Even a very small object can be a major threat.

  Space debris made horrible news on March 20th when a part of an old rocket motor about ten centimeters in size threatened the International Space Station (ISS) . NASA warned the three astronauts inside before the object was to reach the area of the station. The three astronauts quickly moved into the Soyuz emergency escape vehicle as a safety measure. They spent about 11 tense minutes in the capsule. Millions of people were watching the news in front of the televi?sion.

  A more costly incident took place on February 10th. An old Russian military satellite and a United States communications satellite crashed into each other eight hundred kilometers above Siberia in Russia. The collision of the two satellites was the first of its kind in over fifty years of space travel. It spread hundreds of pieces of debris that are larger than one centimeter. Russia launched the Kosmos satellite in1993. But it had not operated for ten years. It was one of hundreds of inactive satellites that remain in orbit. The American Iridium 33 satellite was used for telephone communications. It was owned by Iridium Satellite,a company based in Bethesda,Maryland. The collision was really a loss to the company. But it quickly used another satel?lite as a substitute of Iridium 33 so the collision caused little influence to its service.

  But some even bigger debriscausing events take place sometimes. For example in January,2007,one country tested an antisatellite missile by destroying one of its weather satellites. The test broke the satellites apart into at least two thousand eight hundred identifiable pieces. The debris now circles the earth in orbit from two hundred kilometers to over three thousand eight hundred kilometers.

  Currently,there is no treaty to control the spread of space debris.  Scientists have propounded many ways of cleaning up space,such as using nets,giant collecting arms and powerful laser beams that would move or destroy space junk. But for now,these are just ideas. And,as more nations launch spacecraft,the risk of debris strikes will only grow.

(   ) 5. What makes space debris so destructive?

   A. Its great population. B. Its particular shape.

   C. Its travel speed. D. Its inside structure.

(   ) 6. From the second paragraph we can know that         .

   A. the old rocket motor caused great damage to ISS on March 20th

   B. the news that the old rocker motor made drew great attention from the world

   C. the three astronauts lost their lives in the collision on March 20th

   D. the earth couldn't get in touch with the three astronauts on March 20th

(   ) 7. The last two paragraphs imply that         ,

   A. few rules about protecting the environment of space are being carried out

   B. the development of science will make space a more dangerous place

   C. many countries have agreed on the idea of removing space debris together

   D. using giant collecting arms is the best way of treating space debris

(   ) 8. The underlined word "propounded" in the last paragraph means        .

   A. brought up   B. tried out   C. heard of   D. brought in

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