Lots of scientists believe that there’s life on other planets. Because of this, they keep doing research about the universe. They have sent astronauts to the moon. And they have     1    the answer. There’s no life on the moon. Not long ago they     2     spaceships to Mars. There, they didn’t find life, either. And they found the environment of Mars was     3     from that of the earth. Then they knew it was     4     for people to live on Mars.

    5     they haven’t received a message from other planets, they believe that their idea is right. Recently they have     6     a planet. It’s     7     Proxima Centauri. It’s very     8     to our earth. It is just over four light years away. Proxima Centauri is     9     than the earth. And there’s water on this planet. It     10     mean that life is possible there. Now scientists are studying this planet. Soon they will tell people the answer.

As space science develops, man has learned more and more about space. Space is not only     1     but also dangerous. While working in space, spacemen are facing danger as well as success.

Scientists have     2     out that the radiation (辐射) is the greatest danger to spacemen. When     3     are working in space, they are in danger of the radiation from the sun and other stars, which is bad for their health.

Space     4     is also thought to be a great danger to spacemen. It’s reported that there were 9,000 man-made things flying in space. About 30% of these are satellites, 10% are     5     , and the rest are space rubbish. A small     6     of rubbish even knocks a spaceship window and     7     some damage (损坏).

Scientist are watching and reporting any possible danger all the time. They are working to deal     8     space rubbish.     9     space is really dangerous, it interests many people on the earth. In the near future, it may become     10     for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space in a few years. So we should do something to help improve the space environment.

The moon     1     around the earth. It is quite near to us in     2    . It is only 380,000 kilometres away and man has     3     visited it. So far, no man has travelled     4     than the moon, but spaceships without people have     5     other planets of the universe.

Many countries have     6     up satellites(卫星) into space.

These satellites go     7     the earth and help us to learn more about the earth, the weather and other things. Many countries use these satellites to send and receive     8    . For example,     9     their help, China can send its TV and radio programmes to other countries. We can also use satellites to     10     us make telephone calls to foreign countries.