Laser probe noble gas studies of individual interplanetary dust particles collected in the Earth's stratosphere

Combined noble gas and trace element measurements were performed on 32 chondritic interplanetary dust particles (IDPs) collected in the Earth's stratosphere. The motivations for these analyses were to identify atmospheric entry heating trends and to delineate IDP space exposure lifetimes in an effort to determine their sources. Trace element compositions were determined non-destructively by synchrotron X-ray fluorescence using the X-ray microprobe at the National Synchrotron Light Source, Brookhaven National Lab. Noble gases in each particle were subsequently measured at the Washington University noble gas lab using a laser microprobe.; All but one of the IDPs contained detectable He, and most contained observable quantities of Ne and Ar. The isotopic and elemental compositions of these gases confirm their solar origin, providing evidence that the IDPs were exposed to the solar wind in space.; The Fe-normalized trace element abundances in the IDPs are similar to carbonaceous chondrite meteorite (CI) values with occasional depletions in the more volatile elements, especially Zn. Previous work has suggested a link between Zn losses and instances of severe atmospheric entry heating. Roughly a third of the IDPs in this study have Fe-normalized Zn contents less than ⅓ the CI value. The He concentrations among the Zn-depleted IDPs are significantly lower than in the Zn-normal particles. Correlated losses of Zn and solar wind He proves that most of the Zn-poor particles did indeed experience relatively severe entry heating.; A range of space exposure ages is suggested by the noble gas data. Three particles have gas compositions consistent with brief solar wind exposure (<100 years) implying recent parent body ejection. More lengthy exposure times are indicated by the large concentrations of solar energetic particle (SEP) noble gases present in a subset of the unheated IDPs. Origin at initial orbital distances of greater than 2 AU is suggested for these particles. The presence of cosmogenic 21Ne in two IDPs implies extended exposure to galactic cosmic rays (GCR) and/or solar cosmic rays (SCR). Plausibly these two IDPs record long term (∼200 Ma) exposure to GCRs near the surface of an inactive parent body regolith.