Accretion and compaction of chondrule dust rims

目前关于太阳系起源的理论认为，大量的尘埃和气体在重力作用下坍缩，形成一颗星星，恒星嵌入由物质组成的原行星盘中，行星、卫星、小行星和彗星就是从原行星盘中形成的。 陨石可以提供这些尘埃和气体如何在原行星盘中形成岩石物体的证据。 这一实验室和理论研究方案将解决石质陨石中的球粒周围的细粒尘埃边缘是否会导致它们形成更大的物体，从而成为小行星的组成部分。 贝勒大学和得克萨斯大学奥斯汀分校的本科生将接受现代实验室技术的培训，这项研究将确定陨石球粒堆积的尘埃边缘的初始结构特性。一个数值粉尘凝聚代码与增强处理椭球和带电颗粒将被用来确定压实前的孔隙度，形态，和颗粒排列的球粒在尘埃颗粒水平。碰撞对细粒尘埃边缘（FGRs）压实的影响将使用修改后的冲击物理代码iSALE 2D来计算，以代表多孔FGRs作为边缘球粒或星子之间碰撞的结果。将对冲击波通过含有镶边球粒的材料进行数值模拟。将测量CO、CR和CV试样中FGR的形态、晶粒排列和孔隙率。本实验工作将使用X射线计算机断层扫描、电子背散射衍射和电子探针显微分析来研究FGR如何形成最小改变的碳质方解石。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The present theory of our solar system’s origin involves a massive concentration of dust and gas collapsing under gravity, forming a star that is embedded in a protoplanetary disk of material from which planets, moons, asteroids, and comets form. Meteorites can provide evidence of how this dust and gas formed rocky objects in this protoplanetary disk. This laboratory and theoretical research program will address whether fine-grained-dust rims around chrondrules in stony meteorites can cause them to form larger objects, which become the building blocks of asteroids. Undergraduate students at Baylor University and at the University of Texas at Austin will be trained in modern laboratory techniques.This research will determine the initial structural properties of dust rims accreted by chondrules. A numerical dust coagulation code with enhancements with to treat ellipsoidal and charged grains will be used to determine the pre-compaction porosity, morphology, and grain alignment of chondrule at the dust grain level. The effect of collisions on fine-grained dust rims (FGRs) compaction will be calculated using the shock physics code iSALE2D modified to represent porous FGRs as a result of collisions between rimmed-chondrule or planetesimals. Numerical simulations of the passage of shock waves through material containing rimmed chondrules will be performed. The morphology, grain alignment, and porosity of FGRs in CO, CR, and CV chondrites will be measured. This experimental work will examine how FGRs form minimally altered carbonaceous chondrites using X-ray computed tomography, electron backscatter diffraction and electron Probe microanalysis. These results will be compared to the structural properties obtained in the models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.