My understanding is that metallic spherules from iron meteorites would be expected to include nickel. The absence of nickel in iron containing spherules like these would usually indicate a non-natural source i.e. human technology. The speed and trajectory of the meteor which may be the source, however, indicates an interstellar origin.

I believe that initial analyses of these spherules has revealed an absence of nickel.

The spherules were recovered from areas in the expected debris zone; none were recovered from the surrounding, control zones.