题型：阅读理解 题类：常考题 难易度：普通
内蒙古赤峰市2018-2019学年高二上学期英语期末考试试卷
However exciting space exploration sounds, there's a necessary and important point about it that needs to be considered: food supplies. Right now, astronauts typically rely on dry food in airtight bags and cans, since there are strict weight limits on items taken into space. Foods that we take for granted, such as fresh fruits and vegetables, are out of the question for space explorers.
For those who've made an effort to try to grow food during space flights, they've faced many difficulties, including the absence of gravity, and a lack of soil, air and humidity (湿度). However, growing food to add and minimize (最小化) the food that must be carried to space will be increasingly important on long-duration flights into space. Great efforts have been made to explore the concept (idea) of space farming. Recently, a team led by Federico Maggi at the University of Sydney in Australia have worked out how plants can absorb nutrients from human urine (尿), as was reported by New Scientist on March 27.
After over 20 years of experiments, the results suggested that human urine could supply three to four out of the six nutrients that plants need. The researchers also found out that urine-fertilized plants produce no harmful by-products, such as carbon dioxide or ammonia.
According to New Scientist, human urine is 95 percent water, with the other 5 percent made from nutrients which are harmful to the human body but not to plants. The advantage of this urine-fueled life support system is obvious: By recycling liquid waste and producing food, an efficient cycle will be created.
And most importantly, said New Scientist，the duration of space flights will be greatly extended to “20 years of flight”, meaning we may be soon sending astronauts on flights to Mars, or even beyond.
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