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A rock comet is a rare type of small Solar System body that exhibits features of both a comet and an asteroid, mainly in that it outgasses material primarily made up of grains of rock. ==Description== Rock comets, unlike regular comets, which outgas primarily ice, have comas made of rock. As a result, they can 'outgas' fairly unpredictably, not just when within the frostline. The reason this happens is thought to be similar to how mud cracks at the bottom of a dry lake bed, leaving small chunks loose on the surface of the body, which later get pushed off of it due to radiation pressure sweeping. Sometimes, an object can be mistakenly identified as a rock comet, such as P/2010 A2, an asteroid in the asteroid belt that collided with another object, causing it to have a field of debris trailing it for a short time. Rock comets are rare because a rocky small Solar System body must come very close to the Sun, close enough for both the solid ground to crack, and for there to be enough energy for the separate pieces to be pushed off of the asteroid. However if the asteroid is close enough to the Sun for the former to happen, the latter will also happen. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rock comet」の詳細全文を読む スポンサード リンク
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