  Meteoritic studies of solar system objects show evidence of nucleosynthetic
heterogeneities that are inherited from small presolar grains (< 10 $\mu$m)
formed in stellar environments external to our own. The initial distribution
and subsequent evolution of these grains are currently unconstrained. Using 3D,
gas-dust simulations, we find that isotopic variations on the order of those
observed in the solar system can be generated and maintained by drag and
viscosity. Small grains are dragged radially outwards without size/density
sorting by viscous expansion and backreaction, enriching the outer disc with
presolar grains. Meanwhile large aggregates composed primarily of silicates
drift radially inwards due to drag, further enriching the relative portion of
presolar grains in the outer disc and diluting the inner disc. The late
accumulation of enriched aggregates outside Jupiter could explain some of the
isotopic variations observed in solar system bodies, such as the enrichment of
supernovae derived material in carbonaceous chondrites. We also see evidence
for isotopic variations in the inner disc that may hold implications for
enstatite and ordinary chondrites that formed closer to the Sun. Initial
heterogeneities in the presolar grain distribution that are not continuously
reinforced are dispersed by diffusion, radial surface flows, and/or planetary
interactions over the entire lifetime of the disc. For younger, more massive
discs we expect turbulent diffusion to be even more homogenising, suggesting
that dust evolution played a more central role in forming the isotopic
anomalies in the solar system than originally thought.
