Dependence of the initial internal structure of chondrule rim on dust size distribution
Dependence of the initial internal structure of chondrule rim on dust size distribution
复制标题
球粒边缘初始内部结构对灰尘尺寸分布的依赖性
DOI：
10.1016/j.icarus.2021.114726
复制
发表时间：
2022
期刊：
影响因子：
3.2
通讯作者：
Nakamoto Taishi
中科院分区：
文献类型：
--
作者：
Kaneko Hiroaki;Arakawa Sota;Nakamoto Taishi
陨石中的粗糙物体，如球粒和CAIs，大多被细粒边缘（FGR）覆盖。FGR可以在湍流星云中自由漂浮的球粒表面形成，在那里也会发生尘埃聚集。以前的一项研究报告说，陨石球粒上的尘埃种群的形态影响FGR的初始结构。结果表明，如果单体颗粒增生到球粒上，较小的颗粒倾向于聚集在球粒表面附近，FGR表现出从底部到顶部的粒度变粗。然而，该研究没有考虑粉尘聚集体的时间增长对FGR形成的影响。在这项研究中，我们计算的多分散单体颗粒的聚集和它们的吸积到球粒。粉尘的聚集可分为两个不同的阶段：单体聚集阶段和类BCCA阶段。在单体聚集阶段，当平均聚集体尺寸达到单体的尺寸时，单体颗粒被并入聚集体中。在BCCA类阶段，聚集体分形演化的方式类似于单一尺寸的单体颗粒。在前人研究的基础上，我们得到了球粒获得单体增生FGR的必要条件，并在某些球粒陨石中观察到了晶粒粗化。在与星际介质（ISM）相似的粒度分布情况下，单体吸积需要大于1 μ m的最大粒度（α< 1 0− 3），而如果星云中的湍流强度非常弱（α< 1 0− 5），则需要大于10 μ m的最大粒度。与ISM相比，在大晶粒中具有更大质量分数的单体尺寸分布可能是有效的晶粒尺寸粗化所必需的。
Coarse objects in chondrites such as chondrules and CAIs are mostly coated with fine-grained rims (FGRs). FGRs can be formed on the surface of free floating chondrules in a turbulent nebula, where dust aggregation also occurs. A former study has reported that the morphology of the dust populations accreting onto chondrules affects the initial structures of FGRs. It was revealed that, if monomer grains accrete onto chondrules, the smaller grains tend to accumulate near the surface of chondrules, and FGRs exhibit grain size coarsening from the bottom to the top. However, the study did not consider the effect of temporal growth of dust aggregates on FGRs formation. In this study, we calculate the aggregation of polydisperse monomer grains and their accretion onto chondrules. The following two different stages of dust aggregation can be identified: the monomer-aggregation stage and the BCCA-like stage. In the monomer-aggregation stage, monomer grains are incorporated into aggregates when the average aggregate size reaches the size of the monomer. In the BCCA-like stage, aggregates evolve fractally in a fashion similar to that of single size monomer grains. Based on the results of the previous study, we obtain the requisite conditions for chondrules to acquire monomer-accreting FGRs with grain size coarsening observed in some chondrites. In the case of similar size distribution as that of Inter Stellar Medium (ISM), the maximum grain size of> 1 μ m is widely (α< 1 0− 3) required for monomer accretion, while if turbulent intensity in a nebula is extremely weak (α< 1 0− 5), a maximum grain size∼ 10 μ m is required. The monomer size distributions having larger mass fraction in the large grains compared to ISM might be necessary for the effective grain size coarsening.
登录
查看更多内容
影响因子：
3.2
作者：
C. Xiang;A. Carballido;R. Hanna;L. Matthews;T. Hyde
通讯作者：
T. Hyde
细粒边缘的形成——早期太阳系中高速、动态的尘埃聚集
影响因子：
5
作者：
K. Liffman
通讯作者：
K. Liffman
影响因子：
6.5
作者：
P. Umstätter;H. Urbassek
通讯作者：
H. Urbassek
CM 球粒陨石中球粒和包裹体周围深色地幔的非星云起源
影响因子：
5
作者：
J. Trigo‐Rodríguez;A. Rubin;J. Wasson
通讯作者：
J. Wasson
太阳星云中球粒和尘埃的共同吸积
DOI：
10.1086/587836
发表时间：
2008
期刊：
The Astrophysical Journal
影响因子：
--
作者：
C. Ormel;J. N. Cuzzi;A. Tielens
通讯作者：
A. Tielens