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Scientists are considering the possibility of nding 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 nding 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 tho esntials, though, a Mars mission is impossible.
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A cond problem is that astronauts on the Mars mission would be in the zero-gravity envir家给我
onment 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 decread muscle mass and lower bone density. Over the cour of a two-year mission, the effects would be so vere, they would make it impossible for humans to make the trip without experiencing grave medical problems.
6朵玫瑰代表什么意思Finally, astronauts on a mission to Mars would be expod 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 prent impossible becau it would add too much weight to the ship.
听力原文：
First of all, food, water and oxygen. Well astronauts can u hydroponics. Hydroponics is a technique for growing plants with their roots in water rather than in soil. It requires relati
vely little space. Using hydroponics, the astronauts should be able to cultivate food crops in the spacecraft. In addition, the hydroponic will grow plants with recycle waste water and relea it as clean water vapor, which can be collected as drinking water. And of cour, all plants absorb carbon dioxide and relea oxygen. So thanks to hydroponics the astronauts will also have fresh air to breathe.
Second, the effects of zero gravity. Over the last few decades, we have launched veral space stations orbiting the earth. And a number of astronauts have spent many months on them in a zero gravity environment. The astronauts have learned to u veral techniques to safely manage the effects of zero gravity. For example, regular exerci prevents the decrea in muscle mass. Likewi, taking vitamins and minerals like calcium slows down the decrea in astronauts’ bone density.
Third, solar radiation. Astronauts traveling to Mars will be expod to some solar radiation but this radiation will not be at dangerous levels all the time. The sun only releas dangerous amounts of radiation occasionally, during periods when it is particularly active.
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In order to avoid this threat, the spacecraft could be equipped with special instruments that monitor solar radiation and with a small shelter that shield against radiation but doesn’t add much weight to the ship. Most of the time, the astronauts will go about their normal business in unshielded areas of the spacecraft. But when their instruments detect incread radiation, they could stay in the small shielded area until the danger has pasd.
范文：
Both the reading and listening are arguing over a question whether it is possible to nd human being to Mars. The reading lists out three problems to a successful carrying out. However, the listening offers three solutions to the questions.
First, the reading rais the question that it takes too long to nd people to Mars, approximately two years and no spacecraft could take that many loads of food, water and life esntials. Instead, the listening says this is not a real problem since the astronauts could u hydroponics to grow crop plants in water and food will not be an obstacle. Also,
谈梅生津they could grow plants with recycle waste water and reu it as clean water vapor, which could be drunk. Plus, since all plants do photosynthesis, the astronauts could breathe fresh air relead by them.
Second, the reading asrts that living in a zero-gravity environment would exert a negative effect on one’s health. Nevertheless, the professor says that the astronauts have learned to u veral techniques to make up for the health issue. They will do regular exerci to prevent muscle mass from decreasing and take vitamins and minerals to slow down problem with their bone density. In another word, they’ve figured out how to cope with the potential health problem.
郑国民Third, the reading claims that radiation emitted by the sun would be dangerous to astronauts. This time professor subtly rejects by pointing out that a third solution has come out. The spaceship would be equipped with a special instrument to monitor the radiation. What’s more, the device could also shield against the radiation. When astronauts meet the period of a large amount of radiation, they could hide behind the shielded areas and come out when the danger has pasd.网名怎么取
