Analysis of interplanetary dust particles by soft and hard x-ray microscopy

Interplanetary dust particles (IDPs), fragments from asteroids and comets, contain important clues to the conditions in the solar nebula when dust was forming, provide evidence of the chemical and physical properties of their parent bodies, and may have been an important source of pre-biotic organic matter on the early Earth. We mapped the spatial distributions in IDPs of C, O, K, and Ca using a scanning transmission x-ray microscope and of Fe, Ni, Zn, Sr and Br using fluorescence microtomography. In addition, we obtained carbon and oxygen x-ray absorption near-edge structure (XANES) spectra of the C-rich regions, identifying the C-ring and C=O functional groups, and Fourier Transform InfraRed (FTIR) spectra, identifying the aliphatic C-H₂ and C-H₃ functional groups. The C-mapping indicates that IDPs contain anywhere from a few wt-% up to 90 wt-% carbon, much more carbon than is found in the most carbon-rich meteorites, and C- and O-XANES demonstrate that a significant fraction of this carbon is organic. The Ca, K, Fe, Ni, Zn, Sr, and Br maps allow inference of the host phases of these elements and place constraints on surface contamination.