Is there life on Mars? We don’t know.

We’re sure that people on the earth are not able to live on Mars. People need oxygen to breathe. There is almost no oxygen on Mars.

Living on Mars would be like living on a very high mountain. There would be little air.

The temperature might be 50 degrees above zero at noon and 140 degrees below zero at night. Many people think there may be plants on Mars. We know that on Mars there is carbon. This is a kind of material found in all plants and animals on the earth. Through a telescope, Mars looks red. In some places, it seems gray. At times the gray color turns gray-green, then brown, then gray again. The gray-green color may be a kind of plant life changing color with the seasons.

Will men go to Mars one day? If they do, they must take their own oxygen, food and clothing with them.

In the universe, there is the sun, the moon, the earth and many stars. Through our geography lessons, we know the earth goes around the sun, and the moon goes around the earth. We have day and night because the earth keeps turning all the time. When our part of the earth turns to the sun, it is day. When our part of the earth turns away from the sun, it is night.

Just because the moon is closer to the earth than the sun, it looks much bigger than the sun. Big things will look smaller when they are further, and small things also look bigger when they are nearer.

The sun is big enough to give out very strong light. The moon can’t give any light at all, but it looks quite bright, too. Why? In fact, the light from the moon comes from the sun.

The moon looks much bigger and brighter than the stars. But actually（事实上）the stars are much bigger and brighter than the moon. They look smaller than the moon also because they are further away from the earth.

There are many other planets in the universe. But of all the planets, only on the earth there are living things and people can only live on the earth, too. But at 9:00 a. m. on October 15th, 2003, Chinese pilot Yang Liwei was sent up to space. He stayed there for 21 hours. It was the first time for Chinese to get into space.

①Students enjoy the science class given by astronauts on board China’s Tiangong space station on March 23rd. Wang Yaping, Zhai Zhigang and Ye Guangfu appeared on television screens watched by students across China at 4 p.m. During the 41-minute class, the “teachers”, did four experiments (实验). Let’s take a look at two of them.

②In the first experiment of the class, Wang used a bag of supersaturated sodium acetate solution (过饱和乙酸钠溶液) to show its crystallization (结晶化) in space.

③After Wang pushed the solution hard from the bag, it became a water ball moving slowly in the air, Wang used a small stick cover with crystal nuclei (晶体粉末) to touch the water ball and it quickly became crystallized. “It looks like an ice ball, but as I touch it, I can fell that it is warm.” Wang said.

④Another experiment showed how to separate (分离) oil from water in space. Wang prepared a small bottle of oil and water, which were separated at the beginning, while the students on the earth also had such bottles, allowing them to follow the steps.

⑤The teachers and students shook the bottles to mix oil and water into a mixture (混合物). They found the mixture separated into water and oil again on the earth, but in space water and oil stayed the same as a mixture.

⑥The astronauts said they were so happy to share scientific facts about spaceflight with students. These experiments made young people show greater interest in space and science. Wang Yihan, a ninth grader, said, “It was an eye-opening experience. These experiments really amazed me. I want to be an astronaut too!”

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