细粒边缘的形成--早期太阳系中的高速、动力学尘埃聚集
Fine-grained rim formation -- high speed, kinetic dust aggregation in the early Solar System
摘要:
3型陨石通常含有球粒和耐火内含物,这些内含物被增生的细粒边缘(FGR)覆盖。FGR具有低孔隙率,受到中心定向压力,可能含有高温产物如微球粒,并且在边缘厚度和封闭物体的半径之间存在线性关系。FGR被认为是由灰尘温和地粘附在中心物体上,随后在母体内压缩这个蓬松的边缘而形成的。然而,这个模型不能解释低孔隙度,微球粒和集中的压力。该模型也难以解释边缘厚度和物体尺寸之间的线性关系,包括在该线性关系中存在非零常数。我们建议,FGR形成的尘埃和物体之间的相对高速的相互作用,高初始冲击速度产生磨损,并可能,微球粒。FGR的形成发生在一个较低的速度范围内的真空粘附的碎片从冲击尘埃颗粒的帮助。该模型自然地产生边缘厚度与非零常数、低孔隙度和中心定向压力的线性关系。我们称这个过程为动力学粉尘聚集(KDA),这是工业中使用的气溶胶沉积过程的另一个名称。KDA可能是一个试探性的,部分解释如何尘埃聚集发生在原恒星盘上的路径从尘埃到行星。
英文摘要:
Type 3 chondritic meteorites often contain chondrules and refractory inclusions that are coated with accretionary, fine-grained rims (FGRs). FGRs are of low porosity, were subject to centrally directed pressure, may contain high temperature products like microchondrules and there is a linear relationship between the rim thickness and the radius of the enclosed object. FGRs are thought to have formed by the gentle adhesion of dust onto the central object with the subsequent compression of this fluffy rim within the parent body. However, this model does not explain the low porosity, micro-chondrules and centralized pressure. This model also has difficulties explaining the linear relationship between rim thickness and object size including the existence of a non-zero constant in that linear relationship. We propose that FGRs formed by the relatively high-speed interaction between dust and the object, where high initial impact speed produced abrasion and, possibly, microchondrules. FGR formation occurred over a range of lower speeds aided by vacuum adhesion of fragments from the impacting dust particles. This model naturally produces the rim thickness linear relationship with non-zero constant, low porosity and centrally directed pressure. We call this process kinetic dust aggregation (KDA), which is another name for the aerosol deposition processes used in industry. KDA may be a tentative, part explanation of how dust aggregation occurs in protostellar disks on the pathway from dust to planets.
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