Why is it called Mars? You might have asked yourself this before. Well, Mars is the name of the Roman god of war. People have seen the planet as a symbol of war for thousands of years. The ancient Greeks called the planet Ares after their god of war. Chinese people called it the“fire star" for the same reason.

Scientists have been interested in the planet since long before any space tasks. Egyptian scientists first saw Mars in the sky more than 4,000 years ago. Since then, people from all over the world have studied the planet.

Over the years, scientists have continued to study the planet and learned some basic things about it.

Mars is 10 times lighter and about 6 times smaller than Earth. Earth is 93 million miles (about 150 million km) from the sun, while Mars is 142 million miles away. That means it is much colder on Mars. In fact, the average temperature on Mars is - 62℃. Scientists found water on Mars long ago, but because of the low temperatures there, it is frozen. One day on Mars is called a sol and is about 40 minutes longer than one Earth day. The Red Planet's surface gravity is only 37% as strong as Earth's, meaning you would be able to jump nearly two times higher on Mars.

A． Earth               Mars

B． Earth             Mars

C． Earth               Mars

D． Earth               Mars

【推荐3】① Man has known more and more about space today. Space is not only wonderful but also dangerous. While working in space, astronauts are facing danger.

② Scientists have found out that radiation (辐射) is the greatest danger to astronauts in space. When astronauts are working in space, they are in danger of radiation from the sun and other stars, which is bad for their health. The damage of radiation is difficult to discover until their children or even grandchildren are born. Some special medicine may work a little, but there isn’t really helpful medicine.

③ Space rubbish is also a great danger to astronauts. There are 9000 man-made (人造) things flying in space. About 30% of these are man-made satellites (卫星), 10% are spaceships, and others are space rubbish. Even a small piece of these knocked against a spaceship window and did some damage. Scientists are watching and telling any possible danger all the time. They are working on helpful ways to do with space rubbish.

④ Although space is really dangerous, everyone on the earth is interested in it. In the near future, it may become usual for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space for a few years. So we should care for space and do something to help improve the space environment.

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【推荐2】All living things on Earth need water to live, so water is very important. In fact, the water on Earth is moving around all the time. The water cycle (循环) is a natural course that takes water from the ground and the sky and brings it back to Earth again. This course allows water to move from one part of Earth to another. It is a cycle that happens the whole year and is most active in summer at the mouth of the Yangtze River. In this article, we will explore (探索) the water cycle and discuss its importance for Earth.

The water cycle always begins with water vapour (蒸汽). When it’s hot outside, you can see clouds forming in the sky. These clouds are made of water vapour that comes from the ground, plants and rivers. As water vapour rises into the sky, it cools down and becomes clouds. After that, clouds travel through the sky and fall back to Earth as rain or snow. Then, water runs through rivers and oceans and finally return s to Earth again in different forms like rainwater or snow.

The water cycle plays an important part in protecting our Earth’s climate (气候). It keeps our climate healthy. On top of that, it takes water from rivers and oceans and brings it to the areas that don’t have enough water. Without the cycle, we would face many problems. When there is too much water in one place, it becomes a flood. When water is badly in need, it becomes a drought (旱灾). Besides, water vapour can take heat from the sun and keep our Earth cool.

The water cycle is also an important natural course that keeps our planet alive because it’s important for plants and animals to drink water and for our rivers to stay flowing with water. Understanding the water cycle can help us enjoy the beauty of nature, know how our planet works and develop better ways to protect our Earth. And that is a duty we should take on.

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【推荐3】How can you change negative thoughts? Many people suggest changing your attitude by thinking of something bright and happy.

However, scientists from Queen’s University in Canada said that there might be another way: by walking like a happy person.

“It is not surprising that our mood and the way we feel affects（影响）how we walk, but we want to see whether the way we move also affects how we feel,” explained Nikolaus Troje, the lead scientist, to The Independent.

Scientists believed that the way we remember emotional（令人动情的）messages is affected by our mood. Those who feel sad remember negative information far more easily than active messages, especially when the information is about them.

In order to prove this, Troje and his team used cameras to observe 47 people walking on the treadmill（跑步机）. Half of the people were encouraged to mimic（模仿）a depressive walking style, while the other half moved like a happy person. Walking speed was kept equal for both groups.

During the time on the treadmill, the scientists read out a list of active and negative words, asking people to decide whether or not each word described them well. Afterwards, people were asked to recite as many of the words as they could remember.

As expected, those who had been mimicking a depressed walk remembered more negative words than those that had been walking in a happy manner.

This finding means that our walk influences the way we treat information. And the scientists believe that using a happy walking style could help with treatment for depression.