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美国国家航空和宇宙航行局(NASA)针对天外星体撞击地球的危险,作出了一项称为《太空保卫调查》的研究报告,报告将近地物体依据大小和对地球的威胁分为三类,以甄别它们对地球构成威胁和造成破坏的程度。
The United States National Aeronautics and Astronautics Agency (NASA) made a study called the “Space Guard Survey” on the danger of extraterrestrial collisions with the Earth. The report classified three types of near-Earth objects according to their size and threat to the Earth. Identify the extent to which they pose a threat to the Earth and cause damage.