  The fragile structure of chondritic-porous interplanetary dust particles (CP-
IDPs) and their minimal parent-body alteration have led researchers to believe
these particles originate in comets rather than asteroids where aqueous and
thermal alteration have occurred. The solar elemental abundances and
atmospheric entry speed of CP-IDPs also suggest a cometary origin. With the
return of the Stardust samples from Jupiter-family comet 81P/Wild 2, this
hypothesis can be tested. We have measured the Fe oxidation state of 15 CP-IDPs
and 194 Stardust fragments using a synchrotron-based x-ray microprobe. We
analyzed ~300 nanograms of Wild 2 material - three orders of magnitude more
material than other analyses comparing Wild 2 and CP-IDPs. The Fe oxidation
state of these two samples of material are >2{\sigma} different: the CP-IDPs
are more oxidized than the Wild 2 grains. We conclude that comet Wild 2
contains material that formed at a lower oxygen fugacity than the parent body,
or parent bodies, of CP-IDPs. If all Jupiter-family comets are similar, they do
not appear to be consistent with the origin of CP-IDPs. However, comets that
formed from a different mix of nebular material and are more oxidized than Wild
2 could be the source of CP-IDPs.

Earth and Planetary Astrophysics