  Cook et al. (2021) found that iron meteorites have an initial abundance ratio
of the short-lived isotope $^{60}$Fe to the stable isotope $^{56}$Fe of
$^{60}$Fe/$^{56}$Fe $\sim$ $(6.4 \pm 2.0) \times 10^{-7}$. This appears to
require the injection of live $^{60}$Fe from a Type II supernova (SN II) into
the presolar molecular cloud core, as the observed ratio is over a factor of
ten times higher than would be expected to be found in the ambient interstellar
medium (ISM) as a result of galactic chemical evolution. The supernova
triggering and injection scenario offers a ready explanation for an elevated
initial $^{60}$Fe level, and in addition provides a physical mechanism for
explaining the non-carbonaceous -- carbonaceous (NC-CC) dichotomy of
meteorites. The NC-CC scenario hypothesizes the solar nebula first accreted
material that was enriched in supernova-derived nuclides, and then later
accreted material depleted in supernova-derived nuclides. While the NC-CC
dichotomy refers to stable nuclides, not short-lived isotopes like $^{60}$Fe,
the SN II triggering hypothesis provides an explanation for the otherwise
unexplained change in nuclides being accreted by the solar nebula. Three
dimensional hydrodynamical models of SN II shock-triggered collapse show that
after triggering collapse of the presolar cloud core, the shock front sweeps
away the local ISM while accelerating the resulting protostar/disk to a speed
of several km/s, sufficient for the protostar/disk system to encounter within
$\sim$ 1 Myr the more distant regions of a giant molecular cloud complex that
might be expected to have a depleted inventory of supernova-derived nuclides.
