Mechanical Modification of Chondrule Fine-grained Rims by Dusty Nebular ShocksOPEN ACCESS 

Augusto Carballido, Lorin S. Matthews, Romy D. Hanna and Truell W. Hyde

The Planetary Science Journal, Volume 4, Number 6


“The mechanical processes that convert an initially fluffy chondrule fine-grained rim (FGR) into a more compact structure remain poorly characterized. Given the presence of shocks in protoplanetary disks, we use numerical simulations to test the hypothesis that dust-laden shocks in the solar nebula contributed to FGR modification. We use the iSALE2D shock physics code to model the collision of dusty nebular shock fronts (which we term “dust clouds”) into chondrule surfaces that host a porous FGR. In our simulations, dust particles are modeled as dunite disks. The dust radii follow the Mathis–Rumpl–Nordsieck distribution of interstellar grains. Chondrules are modeled as rectangular dunite slabs. We vary the impact speed vimp, the fractional abundance fcloud of dust grains in the impacting shock, and the fractional abundance fFGR of dust grains in the pre-existing FGR. We thus compute dust temperatures and pressures resulting from the collisions, as well as the net mass accretion of dust by the FGRs. Dust temperatures increase upon impact, depending on the kinetic energy of the dust cloud and on fFGR. Dust rims with a higher fFGR heat up more than those with a lower fFGR, with possibly important implications for the composition and structure of FGRs. Maximum impact pressures increase with fcloud. Fine-grained rims can experience mass gain from the impacting cloud, but in some instances, mass is lost from the rim. We find qualitative similarities in the topography of the FGR–chondrule interface between our simulations and petrographic analyses of the Paris CM chondrite by other authors.”