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We've all heard of mermaids. They are the beautiful half-human, half-fish creatures(生物). They have the head and body of a human and the tail of a fish. We also know that mermaids only exist in fairy tales. But where did all the stories about these creatures come from? If you have ever seen a manatee, then you might have an idea.
Manatees, which are also called sea cows, are mammals(哺乳动物) that live in the sea. Since they are mammals, they have to swim up to the surface to breathe air. Many people believe that the story of the mermaid began with the ancient sailors who saw the manatees putting their heads out of the water to breathe. Because manatees are upright when they do this, it looks like they are standing. If a sailor saw a manatee doing this from far away across the sea, it is possible that the sailor would mistake the manatee for a creature that is half-human, half-fish.
Mermaids are described as having very long hair. This is probably because manatees like to swim up to the surface of the water in areas where there is sea grass. Manatees eat all kinds of plants in the sea, including sea grass. The sea grass around the manatee's head when they eat could create a picture of long hair.

Manatees also have powerful tails that are very similar to the fish-like tail of a mermaid. The sailors probably watched manatees come up for air and then swim back below the surface, using their paddle-shaped tails. This would explain why the sailors thought mermaids had fish-like tails.

      Do you know how many pandas there are in the world? World Wildlife Fund (WWF) has spent four yours counting pandas in the world. It says there are 1,590 now. In the 1980s, there were only 1,100.

So we may say that pandas are lucky because people around the world love them and are trying their best to help them. However, we also say that pandas are unlucky because they are still facing a lot of problems now.

Pandas are not good at making babies. Even in the wild, scientists have found that female pandas give birth only every 28 months. That's why the number of pandas goes up so slowly.

Pandas need bamboos for food, but bamboo dies every 10 to 100 years. It can take up to 20 years to provide(提供) food for pandas. When bamboo dies, pandas have to move to other areas. In the past, this was easy. However, the number of people keeps growing, people cut down more forests and built more villages. It's more difficult for pandas to find bamboos and homes than before.

In the past years, WWF made great efforts to protect pandas. And some Chinese scientists are also always trying to find ways to help pandas.

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    Jupiter(土星) is the fifth planet from the sun and it is the largest one in the solar system. It is about 11 times bigger than the earth. Jupiter's strangest thing is its huge red spot. Pictures taken from space tell us that the red spot is probably a hurricane(飓风). It is so big that the earth would fit right in the middle of it. Sometimes the hurricane looks like a huge oven with orange-red waves (波浪). Some other time the color almost disappears.

    On the earth, hurricanes move. We can watch them travel across water to land. Jupiter's red spot also moves. Scientists say it “walks”. It is carried along by air in Jupiter's atmosphere(大气层).

    So far, Jupiter has been visited by four spacecrafts. All of them flew by Jupiter very quickly. On the next trip to Jupiter, a spacecraft will stay near the planet much longer. New information will be sent back to the earth. Soon scientists will know much more about this strange red spot in the atmosphere.

    Every living thing on Earth is either a plant or an animal, right? Wrong! Many organisms（有机体）in our world are neither. Some of them float through the air, and some lie hidden in the ground. They do not need sunlight to survive, and if the weather becomes too cold, they can become inactive until conditions improve.

    What are these? They are called fungi(菌类), and you see them almost every day. Many kinds of fungi seem disgusting, such as the green black things that appear on the food which are left too long in the refrigerator. But other kinds are not so bad. For example, the yeast that is used to make bread and mushrooms (蘑菇) are both fungi.

    What makes fungi different from plants and animals? An animal can move around by itself. Fungi get around too, but they don't have feet, wings, or tails. They have to wait for wind or some other outside force to move them. Plants are different from fungi because they have chlorophyll（叶绿素）. It helps them make food from the energy in sunlight. Fungi do not have chlorophyll.

    Some fungi are bad, while others are not. Some fungi cause diseases, such as athlete's foot, which makes feet uncomfortable. Other kinds of fungi can be used to make medicines, which have saved many lives.

    Fungi clean up more than wounds, though. They are the world's first recyclers. Without fungi, our world would be a mess. Since fungi cannot make their own food as plants do, they must get their food elsewhere. Many fungi get their food from dead plants. They break them down and turn them into soil. The fungi get a meal, and the world gets a housecleaning.

    The movie The Martian (《火星救援》) is very popular among space lovers. It shows an astronaut trying to live on Mars.

    Although the idea of living on Mars is great, the reality does not look so good. Mars does not have a friendly atmosphere (大气层) for humans. There is very little oxygen there. And because it is too far away from the sun, it is also very cold there. Sometimes the temperature on Mars can be -133℃. This is much too cold for humans.

    However, scientists say it might be possible to live there even without a good atmosphere. Daytime on Mars is almost the same as Earth's. It means there's enough sunlight to grow plants inside safe buildings. However, they would have to grow in soil from Earth. Mars does not have a strong enough atmosphere to stop the radiation (福射) coming from space, which makes it dangerous to grow things in the soil.

    The radiation also causes problems for our health. One way to live there is to build homes underground or in the rocks on the planet. This can help humans keep away from the radiation and keep warm.

    When could we live on Mars? Scientists are hoping to make it possible to live on Mars. Let's wait and see.