Surface analysis of stratospheric dust particles

A controversially discussed and yet central question in interplanetary dust particle (IDP) research is the degree of alteration of these particles dur ing their residence in the stratosphere. Especially, the typical enrichment of Br in chondritic IDPs (on the average similar to 21 x CI) has been infe rred to be a result of contamination processes, probably invoking aerosol d roplets. With time-of-flight secondary ion mass spectrometry (TOF-SIMS), we examined the surfaces of 13 stratospheric particles from the dust collecto r U2071. Six particles had severe, surface-bound, silicone oil residues pre venting 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 partic le, 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 e vidence for a surface correlation of halogens. This evidence, taken togethe r with that from previous studies, proves a general stratospheric contamina tion process which has to be considered in IDP research.