Injection of isotopic anomalies into the early solar nebula

Detailed hydrodynamic calculations are used to constrain models of the early solar system which rely on external injection of isotopically anomalous matter to explain meteorite anomalies. The conditions studied resemble a supernova remnant shell impacting on the outside of an interstellar H I cloud. For injection of either grains or gas, the essential physics of any such injection process is determined before the impinging material can penetrate beyond a skin layer, so that the results for an H I edge should be valid for any configuration which joins the interstellar medium with an H I boundary zone. The effects of initial injection velocity, gas cooling, and magnetic fields are considered. It is shown that grain penetration is limited to a layer with column density on the order of the grain mass/area ratio. Rayleigh-Taylor instabilities of the gas contribute negligibly to penetrate in the early stages, but do lead to the formation of bubbles (diameter approx.1011 cm) of anomalous matter, which may be dispersed in later evolution. In the cases studied, the anomalous matter accumulates in the outer regions of the target cloud. The detailed hydrodynamics of these regions indicates that shock heating at impact, differential penetration by grains, and the observed compositions of meteorites can be combined into a consistent scenario in which grain injection by a supernova remnant leads to the formation of anomalous meteorite parent bodies in the outer regions of the early solar nebula. Some considerations regarding turbulence are discussed in relation to these results