GRAIN SORTING IN COMETARY DUST FROM THE OUTER SOLAR NEBULA
GRAIN SORTING IN COMETARY DUST FROM THE OUTER SOLAR NEBULA
复制标题
太阳系外星云彗星尘埃中的颗粒分选
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
M. Price
中科院分区：
文献类型：
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作者：
P. Wozniakiewicz;J. P. Bradley;H. Ishii;D. Brownlee;A. Kearsley;M. Burchell;M. Price
大多数年轻恒星都被气体和尘埃组成的圆盘包围着。在靠近热星的地方，来自母分子云的无定形尘埃颗粒被再加工成晶体，然后分布在整个吸积盘中。在一些圆盘中，随着离恒星的日心距离的增加，晶体颗粒尺寸变小。我们研究了球粒状多孔(CP)行星际尘埃粒子(IDP)中的晶体粒度分布，这些尘埃粒子被认为来自于太阳星云外部区域聚集的小冰体。颗粒为富镁硅酸盐和富铁硫化物，这是CP IDPs中最丰富的两种矿物。我们发现，它们的半径主要为-lt；0.25μm，平均粒度随CP IdP的不同而不同。我们报道了硅酸盐和硫化物之间的尺寸-密度关系。小行星带陨石中大得多的硅酸盐和硫化物颗粒之间的大小-密度关系被归因于空气动力学分选。由于CP IDP中的硅酸盐和硫化物颗粒理论上太小，不适合空气动力分选，它们的尺寸-密度关系可能是由于另一种能够分选小颗粒的过程。
Most young stars are surrounded by a disk of gas and dust. Close to the hot stars, amorphous dust grains from the parent molecular cloud are reprocessed into crystals that are then distributed throughout the accretion disk. In some disks, there is a reduction in crystalline grain size with heliocentric distance from the star. We investigated crystalline grain size distributions in chondritic porous (CP) interplanetary dust particles (IDPs) believed to be from small, icy bodies that accreted in outer regions of the solar nebula. The grains are Mg-rich silicates and Fe-rich sulfides, the two most abundant minerals in CP IDPs. We find that they are predominantly <0.25 μm in radius with a mean grain size that varies from one CP IDP to another. We report a size–density relationship between the silicates and sulfides. A similar size–density relationship between much larger silicate and sulfide grains in meteorites from the asteroid belt is ascribed to aerodynamic sorting. Since the silicate and sulfide grains in CP IDPs are theoretically too small for aerodynamic sorting, their size–density relationship may be due to another process capable of sorting small grains.