| Abstract: | Abstract— A controversially discussed and yet central question in interplanetary dust particle (IDP) research is the degree of alteration of these particles during their residence in the stratosphere. Especially, the typical enrichment of Br in chondritic IDPs (on the average ～21 × CI) has been inferred to be a result of contamination processes, probably invoking aerosol droplets. With time-of-flight secondary ion mass spectrometry (TOF-SIMS), we examined the surfaces of 13 stratospheric particles from the dust collector U2071. Six particles had severe, surface-bound, silicone oil residues preventing a proper analysis of their surfaces. Six other particles—-according to our scanning electron microscopy, energy dispersive x-ray spectrometer (SEM-EDS) studies preclassified as one (Fe,Ni)S-rich IDP, one Ca-rich particle, and four aluminum-oxide spheres—-carry the halogens F, Cl, and Br on the surface. At least for the aluminum-oxide spheres, we provide unequivocal evidence for a surface correlation of halogens. This evidence, taken together with that from previous studies, proves a general stratospheric contamination process which has to be considered in IDP research. |
