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托福写作-综合-TPO50 谢谢老师

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发表于 2017-8-17 20:00 |显示全部楼层
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Scientists are considering the possibility of sending humans to Mars in the coming decades. Although there have been successful manned missions to the Moon in the 1960s and 1970s, Mars is 150 times further away from Earth than the Moon is. Thus the project of sending humans to Mars would require solving an array of problems the Moon missions did not have to face.One problem is that a round-trip to Mars and back is likely to take at least two years. The trip to the Moon lasted only a few days, and it was easy to bring enough supplies of food, water, and oxygen; but the cargo capacity of space vehicles is too limited to put on board the food, water, and oxygen required by a crew for a period of two years. Without those essentials, though, a Mars mission is impossible.A second problem is that astronauts on the Mars mission would be in the zero-gravity environment of space for many months at a time. Spending a long time in the zero-gravity environment has negative effects on the human body, such as decreased muscle mass and lower bone density. Over the course of a two-year mission, the effects would be so severe, they would make it impossible for humans to make the trip without experiencing grave medical problems.Finally, astronauts on a mission to Mars would be exposed to dangerous levels of space radiation, much of which comes in the form of charged particles emitted by the Sun. Earth's magnetic field, which normally protects us from dangerous solar radiation, would not be able to protect a spaceship traveling in interplanetary space. Constructing a shield that would protect the whole spaceship from space radiation is at present impossible because it would add too much weight to the ship.      Summarize the points made in the lecture, being sure to explain how they respond to the specific concerns presented in the reading passage.


In the reading, the writer contends that there are many problems should be solved when we send humans to Mars and it seems impossible.  However, the professor in the lecture believes the scientists have found the solutions. The professor's lecture casts doubt on the reading.

To begin with, the author claims that there is no space to carry so much food and water for two years. However, the lecturer refutes that the scientist created the technique which uses much less  space than before. What's more, we have the technique to cultivate plants in the spacecraft and produce clean water and fresh air.

Moreover, the author believes that the astronauts will not stay in the zero-gravity environment for long time. On the contrary, the lecturer rebuts that we have the space station now and the astronauts live there for many months. We also have the training system to keep the astronauts health. For example,
the astronauts do exercise everyday in order to get far away from low bone density.

Finally, the author puts forward that the space radiation would be harmful to the spaceship. Instead, the lecturer retorts that the radiation is not dangerous all the time. It's occasionally. We also have the instrument which can make a small shelter and  protect the spacecraft from space radiation. The instrument will not add too much weight.


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