Dynamics of high-temperature materials delivered by jets to the outer solar nebula

Abstract

The presence of high-temperature materials in the Stardust collection that are isotopically similar to those seen in chondritic meteorites argues for the outward transport of materials from the hot, inner region of the solar nebula to the region where comets formed. A number of mechanisms have been proposed to be responsible for this transport, with a number of models being developed to show that such outward transport is possible. However, these models have not examined in detail how these grains are transported after they have been delivered to the comet formation region or how they may be distributed in the cometary nuclei that form. Here, the dynamical evolution of crystalline silicates injected onto the surface of the solar nebula as proposed by jet models for radial transport is considered. It is generally found that crystalline grains should be heterogeneously distributed within the population of comets and within individual cometary nuclei. In order to achieve a homogeneous distribution of such grains, turbulence must be effective at mixing the crystalline silicates with native, amorphous grains on fine scales. However, this turbulent mixing would serve to dilute the crystalline silicates as it would redistribute them over large radial distances. These results suggest that it is difficult to infer the bulk properties of Wild 2 from the Stardust samples, and that the abundance of crystalline grains in these samples cannot alone be used to rule out or in favor of any of the different radial transport models that have been proposed.