  There is a wealth of data on live, undecayed 60Fe ($t_{1/2} = 2.6 \ \rm Myr$)
in deep-sea deposits, the lunar regolith, cosmic rays, and Antarctic snow,
which is interpreted as originating from the recent explosions of at least two
near-Earth supernovae. We use the 60Fe profiles in deep-sea sediments to
estimate the timescale of supernova debris deposition beginning $\sim 3$ Myr
ago. The available data admits a variety of different profile functions, but in
all cases the best-fit 60Fe pulse durations are $>1.6$ Myr when all the data is
combined. This timescale far exceeds the $\lesssim 0.1$ Myr pulse that would be
expected if 60Fe was entrained in the supernova blast wave plasma. We interpret
the long signal duration as evidence that 60Fe arrives in the form of supernova
dust, whose dynamics are separate from but coupled to the evolution of the
blast plasma. In this framework, the $>1.6$ Myr is that for dust stopping due
to drag forces. This scenario is consistent with the simulations in Fry et. al
(2020), where the dust is magnetically trapped in supernova remnants and
thereby confined around regions of the remnant dominated by supernova ejects,
where magnetic fields are low. This picture fits naturally with models of
cosmic-ray injection of refractory elements as sputtered supernova dust grains
and implies that the recent 60Fe detections in cosmic rays complement the
fragments of grains that survived to arrive on the Earth and Moon. Finally, we
present possible tests for this scenario.
