陨石、流星体与小行星及彗星的演化关系

小行星、彗星和流星体(meteoroid)都是绕太阳公转的小天体,它们只是在轨道特性和物理-化学性质方面有所不同,流星体泛指在行星际空间运行的、质量从10~(-16)克微流星体或微尘到10~8克的所有小天体,当它们闯入地球大气时与大气剧烈碰撞而产生发光的流星(meteor)现象,落到地面的流星体残余则称为陨石或陨星(meteorite)。

EVOLUTIONARY RELATION BETWEEN METEORITES,METEOROIDS AND ASTEROIDS OR COMETS

In this paper,the evolutionary relation between meteorites,meteonoids and asteroids or comets is discussed in our viewpoint on the origin of asteroids and comets.Both asteroids and comets are the'halffinished product' of the planets evolved from the primitive nebula,i.e.surviving planetesimals.They show differences in their evolutions,in their orbital characters and their physics-chemical properties only because they form in different places,under different environmental conditions.When volatile-rich comets moved into inner portion of the solar system,they could easily disintegrate into a great number of meteoroids.The surviving planetesimals in the asteroid region could be broken into fragments by collision.Those fragments and crumbs could turn into smaller asteroids or meteoroids.In fact,there is no strict limits between smaller asteroids and bigger meteoroids.Some fragments of planetesimals in the asteroid region would evolve into meteoroids and enter into the atmosphere of the earth,they could then ablaze out as meteors.Cosmic dust,which failed into the solar system from interstellar space,could also become meteoroids