[揽瓜阁精读] 276. 陨石和星云

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276陨石和星云 又臭又长 30’
P1: NEAR study the asteroid
P2: NEAR spiral round the asteroid and reveal what it is made of and help to solve a problem: connection between asteroids and meteorites（陨石）
P3: scientists suspect meteorites spawn from asteroids but there are few clues. Hope NEAR can resolve the conundrum（难题，谜语）
P4:asteroid belt contains thousands of minor planets that are remnants（残余）of innumerable small bodies condensed（凝结，压缩）when Solar S formed and never merge into a single large one
P5:reach earth的asteroid escape from the belt and head to Sun to cross earth’s orbit(evidence 1932) MP&KP: asteroids approaching the earth is normal
P6: asteroids supply continually replenished, asteroids come from main asteroid belt
P7: how to escape? Asteroid fragments perturbed（扰乱 v.）by gravity propelled（推进）out of the belt and cross Earth’s orbit or fall into atmosphere as burning meteors（流星）
P8: 造成meteor showers的comets小 而且容易在地球大气层就燃烧殆尽， 但是asteroid的碎片能扛过fiery plunge and hit the earth and be displayed in the museum.
P9:most common meteorites made from the same stuff as the Sun, so chondritic meteorites maybe also formed from Earth and other terrestrial planets.
P10: earth, moon, and other planets evolved（进化，演变）dramatically.