Abstract
Two interplanetary dust particles (IDPs) investigated by NanoSIMS reveal diverse oxygen isotope compositions at the micrometre-scale. The oxygen isotope values recorded at different locations across the single IDP fragments cover a wider range than the bulk values available from all IDPs and bulk meteorites measured to date. Measurement of H, C, and N isotopes by NanoSIMS, and the use of scanning and transmission electron microscopy (SEM and TEM) to determine elemental compositions and textural information allows for a better understanding of the lithologies and organic signatures associated with the oxygen isotope features.IDP Balmoral, a ∼15μm-sized fragment with a chondritic porous (CP)-IDP-like texture, contains a region a few micrometres in size characterised by 16O-depleted isotope signatures in the range δ17O, δ18O=+80‰ to +200‰. The remainder of the fragment has a more 16O-rich composition (δ18O=0–20‰), similar to many other IDPs and bulk meteorites. Other than in discrete pre-solar grains, such extreme 16O-depletions have only been observed previously in rare components within the matrix of the Acfer 094 meteorite. However, TEM imaging and FeO/MgO/Si ion ratios indicate that the 16O-depleted regions in Balmoral did not form by the same mechanism as that proposed for the 16O-depleted phases in Acfer 094. As the level of 16O depletion is consistent with that expected from isotope selective self-shielding, it is likely that the 16O-depleted reservoir was located close to that where oxygen self-shielding effects were most pronounced (i.e., the outer solar nebula or even interstellar medium).Individual regions within IDP Lumley cover a range in δ18O from −30‰ to +19‰, with the oxygen isotope values broadly co-varying with δD, δ13C, δ15N, light-element ratios and texture. The relationships observed in Lumley indicate that the parent body incorporated material at the micrometre-scale from discrete diverse isotopic reservoirs, some of which are represented by inner Solar System material but others which must have formed in the outer Solar System.The IDP fragments support a model whereby primary dust from the early solar nebula initially formed a variety of reservoirs in the outer solar nebula, with those at lower AU incorporating a higher proportion of inner Solar System chondritic dust than those at larger AU. These reservoirs were subsequently disrupted into micrometre-sized clasts that were re-incorporated into IDP parent bodies, presumably at large AU. These results reveal that any models accounting for mixing processes in the early solar nebula must also account for the presence of an extremely 16O-depleted reservoir in the comet-forming region.
Highlights
IntroductionLaboratory analysis of Interplanetary dust particles (IDPs) has revealed their primitive nature, such as high abundances of presolar grains (Messenger et al, 2003; Floss et al, 2006; Busemann et al, 2009; Davidson et al, 2012), the presence of GEMS (Glass with Embedded Metal and Sulphides; Bradley, 1994; Keller and Messenger, 2011) and an abundance of primitive carbonaceous material (Messenger, 2000; Floss et al, 2006; Busemann et al, 2009; Matrajt et al, 2012; Starkey et al, 2013)
Laboratory analysis of Interplanetary dust particles (IDPs) has revealed their primitive nature, such as high abundances of presolar grains (Messenger et al, 2003; Floss et al, 2006; Busemann et al, 2009; Davidson et al, 2012), the presence of GEMS (Glass with Embedded Metal and Sulphides; Bradley, 1994; Keller and Messenger, 2011) and an abundance of primitive carbonaceous material (Messenger, 2000; Floss et al, 2006; Busemann et al, 2009; Matrajt et al, 2012; Starkey et al, 2013). These primitive features suggest it is likely that IDPs provide access to samples of the early Solar System from bodies that are otherwise hard to access from Earth, and which may never have been sampled by meteorites, or survived the aqueous and/or thermal alteration processes experienced by meteoritic material on parent asteroids
The results of this study confirm that IDPs are important samples for preserving information about early Solar System reservoirs that are not readily available from, or preserved in, samples originating from asteroids
Summary
Laboratory analysis of IDPs has revealed their primitive nature, such as high abundances of presolar grains (Messenger et al, 2003; Floss et al, 2006; Busemann et al, 2009; Davidson et al, 2012), the presence of GEMS (Glass with Embedded Metal and Sulphides; Bradley, 1994; Keller and Messenger, 2011) and an abundance of primitive carbonaceous material (Messenger, 2000; Floss et al, 2006; Busemann et al, 2009; Matrajt et al, 2012; Starkey et al, 2013) These primitive features suggest it is likely that IDPs provide access to samples of the early Solar System from bodies that are otherwise hard to access from Earth, and which may never have been sampled by meteorites, or survived the aqueous and/or thermal alteration processes experienced by meteoritic material on parent asteroids
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