【推荐1】Billions of dollars have already been spent in planning how to set foot on Mars. So why do we want to go there so badly?     1    　

Dutch organization Mars One wants to put people on Mars by 2027. The researchers say it is just the next step in human curiosity (好奇心). “Why did Columbus travel west? Why did Marco Polo head east?     2     ” their website says. Mars One also thinks Mars exploration will improve the development of recycling, solar energy (太阳能), food production and even medical technology.

Billionaire businessman Elon Musk runs a company in the United States. Its name is Space X.     3     Musk, who was born in South Africa but is now a US-Canadian citizen, agrees that curiosity plays a part. But his main reason for going to Mars is the survival (生存) of the human race. To survive, we must learn to live somewhere other than Earth.

    4     In 2011, along with Russia, China planned to send a probe (探测器) to the planet. Another probe will reach Mars by 2021.

US space agency NASA is also excited to get to Mars.     5     “Future exploration will find evidence (证据) of life, answering one of the biggest mysteries of the universe (宇宙): Does life exist beyond Earth?” the NASA website says. According to it, Mars and Earth have lots of things alike. Exploring Mars also helps us learn more about our own planet’s history and future.

【推荐2】①Every now and then you may see news of satellites sent into space. On Feb 21, for example, US company Space X took 46 satellites into orbit. On Feb 27, China sent 22 satellites into space. Why do we need so many satellites? What do they do out there?

②At present, there are more than 3,000 satellites moving around the Earth, according to Germany. Satellites are very helpful to humans. They do all kinds of work, from transmitting (传送) TV signals to giving you directions on the road to helping scientists do research.

③For example, the 22 satellites China just sent up are part of the Beidou Navigation Satellite System. Shared bikes that use BeiDou chips can be easier to find. Drones (无人机) can also use BeiDou to fly.

④Before satellites, TV signals didn’t go very far. Mountains or tall buildings would stop them. Phone calls to faraway places were also a problem. With satellites, TV signals and phone calls can be sent directly to a satellite and back down to different places on Earth.

⑤Satellites can also provide information about clouds, oceans, land and ice. They help scientists predict changes in weather. By monitoring (监测) wildfires and volcanoes, satellites help people deal with natural disasters. Farmers can use satellite pictures to decide the best time to water their fields.

⑥Some satellites fly near other planets. They may look for water on Mars or take close-up pictures of Saturn’s rings (土星环). In 2020, Bilibili sent a satellite into space. Its job is to look at other planets and share the pictures and videos with Bilibili’s users.

【推荐3】The world is a beautiful place in our eyes. But does it look the same through the eyes of animals?

Dogs

They can’t see as many colors as we can. They can see blues, browns and yellows. They have fewer color-detecting cells（色彩感知细胞）than humans do.

Jumping Spiders

They have eight pairs of eyes. They can see more colors than humans. They can see ultraviolet light（紫外线）. So they see things clearer than we do.

Rats

They can move one eye in different directions while keeping the other eye stop moving. It is to see their enemies better. They can’t see many colors. It’s not necessary because they mostly come out at night. They are good at seeing bright light.

Horses

They have eyes on either side of their head. So they see wider（视野更宽阔）than humans. They have a blind spot（盲点）in front of their nose. They can’t see as many colors as humans do. They can see greens and blues; but most of the time they see grays.

【推荐2】Are you a shy person？Do you expect to become outgoing？Being outgoing can help a lot in your life. In fact, being outgoing is not so hard as you think. Here is some advice on how to become outgoing.

You can start to try becoming outgoing when you stay with your friends. But the real challenge (挑战) comes when you meet strangers or new friends.

Smile at them, and usually they will smile at you, too. You may find it easy to start talking in this way.

Start a talk positively (积极地).Try to speak first. Simple greetings such as “Hello！”“How is it going？” and “It's a little cloudy today, isn't it？”are a good start. After that, you can talk more. For example, you can talk about the latest news. But you'd better read some news in newspapers and have your own ideas first. Or you may find that you won't have much to say. The best way to become outgoing is to go out. It is also a very important step. Usually those who like to do the same things can communicate (交流) better. If you like playing sports, go to a sports club. You may make many new friends there if you get over your shyness.

【推荐3】Your brain controls everything you do. It makes it possible for you to think, learn, create and feel; to blink(眨眼)and breathe and for your heart to beat--this fantastic control center is your brain. It is so amazing that a famous scientist once called it “the most complex (复杂) thing we have yet discovered in our universe.”

Can this small grey organ (器官) , which weighs less than one and a half kilos, really do so much? Amazingly, your brain contains about 100 billion neurons (神经元) --it would take you over 3,000 years to count them all. Believe it or not, the activity in your brain never stops. Your neurons create and send more messages than all the phones in the world. And although one neuron create only a little electricity, all your neurons together can produce enough electricity to power a light bulb (灯泡).

So exactly how fast does your brain work? Well, imagine this: a bee lands on your foot. Neurons in your skin send this information to your brain at a speed of more than 240 kilometers per hour, Your brain then uses other neurons to send the message back to your foot to shake the bee off quickly. These neurons can send this information at more than 320 kilometers per hour. No computer has your brain's unbelievable ability to deal with the amount of information coming from your eyes, ears and other sensory organs.

But how does your brain allow you to learn things that you will use in the future? The structure(结构)of your brain changes every time you have a new thought, remember or learn something. For example, riding a bike seems impossible at first, but soon you are able to do it. How? As you practice, your brain sends “bike riding” messages again and again. Soon, the actions are learnt and you are able to ride a bike easily from then on.