Two 10-μm interplanetary dust particles collected in the stratosphere, have been analyzed with X-ray fluorescence excited by white synchrotron radiation (SYXFA) at the HASYLAB (DESY) in Hamburg. The measured abundances of the minor and trace elements with 16 < Z < 76 are in good agreement with abundances determined by PIXE analysis [1] of the same particles.
The results demonstrate that SYXFA is indeed a powerful
non-destructive technique for multi-element analysis of
micron-sized samples. Moreover we find that the combined
application of two such techniques, SYXFA and PIXE, to the same valuable particle lends high credibility to the results.
Cometary dust grains as measured by the Halley space missions show a silicate- and a light element component. The latter most likely represents an organic material. The densities of the grains are mostly below 1 g/cm^2. The organic component slowly decays at higher temperatures during subsequent perihelion passages. Therefore the "older” cometary grains are different from the "young" cometary grains: they show higher albedos, higher densities and orbit finally within the inner solar system.
Comets and asteroids are thought to be the main sources of interplanetary dust particles (IDPs). IDPs with a diameter < 50 um are able to survive the entry into the Earth's atmosphere, where they can be collected without destruction. Because of their small size and mass, typically <10 um and <10~^9 g, their chemical analysis iscdifficult. We introduce the proton microprobe for the
non-destructive detection of trace elemente in IDPs. Using the Heidelberg proton microprobe which provides a beam spot of < 2x3 um^2, four IDPs have been analyzed and up to 26 elements were detected. To quantitatively evaluate the proton-induced X-ray spectra we calculated ab initio Xray yields for the samples. Most elemental abundance ratios in three IDPs agree within a factor of two with those of cosmic abundance but with the notable exception of some volatile elements (P, Cu, Ga, Br, and Zn) which are strongly enriched. This is contrasting one IDP in which Ca and the volatile elemente K, Zn and S are depleted.