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关于伤感的句子
上海大学材料学院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.蜘蛛寿命>显卡维修
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土木工程包括哪些专业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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