  Iron-60 (t1/2=2.62 Myr) is a short-lived nuclide that can help constrain the
astrophysical context of solar system formation and date early solar system
events. A high abundance of 60Fe (60Fe/56Fe= 4x10-7) was reported by in situ
techniques in some chondrules from the LL3.00 Semarkona meteorite, which was
taken as evidence that a supernova exploded in the vicinity of the birthplace
of the Sun. However, our previous MC-ICPMS measurements of a wide range of
meteoritic materials, including chondrules, showed that 60Fe was present in the
early solar system at a much lower level (60Fe/56Fe=10-8). The reason for the
discrepancy is unknown but only two Semarkona chondrules were measured by
MC-ICPMS and these had Fe/Ni ratios below ~2x chondritic. Here, we show that
the initial 60Fe/56Fe ratio in Semarkona chondrules with Fe/Ni ratios up to
~24x chondritic is 5.4x10-9. We also establish the initial 60Fe/56Fe ratio at
the time of crystallization of the Sahara 99555 angrite, a chronological
anchor, to be 1.97x10-9. These results demonstrate that the initial abundance
of 60Fe at solar system birth was low, corresponding to an initial 60Fe/56Fe
ratio of 1.01x10-8.
