Mass Spectum Imaging of Organics Injected into Stardust Aerogel by Cometary Impacts

Comets have largely escaped the hydrothermal processing that has affected the chemistry and mineralogy of even the most primitive meteorites. Consequently, they are expected to better preserve nebular and interstellar organic materials. Organic matter constitutes roughly 20-30% by weight of vol-atile and refractory cometary materials [1,2]. Yet organic matter identified in Stardust aerogel samples is only a minor component [3-5]. The dearth of intact organic matter, fine-grained and pre-solar materials led to suggestions that comet 81P/Wild-2 is com-posed largely of altered materials, and is more similar to meteorites than the primitive view of comets [6]. However, fine-grained materials are particularly susceptible to alteration and destruction during the hypervelocity impact. While hypervelocity capture can cause thermal pyrolysis of organic phases, some of the impacting organic component appears to have been explosively dispersed into surrounding aerogel [7]. We used a two-step laser mass spectrometer to map the distribution of organic matter within and sur-rounding a bulbous Stardust track to constrain the dispersion of organic matter during the impact

NM-Scale Anatomy of an Entire Stardust Carrot Track

Comet Wild-2 samples collected by NASA s Stardust mission are extremely complex, heterogeneous, and have experienced wide ranges of alteration during the capture process. There are two major types of track morphologies: "carrot" and "bulbous," that reflect different structural/compositional properties of the impactors. Carrot type tracks are typically produced by compact or single mineral grains which survive essentially intact as a single large terminal particle. Bulbous tracks are likely produced by fine-grained or organic-rich impactors [1]. Owing to their challenging nature and especially high value of Stardust samples, we have invested considerable effort in developing both sample preparation and analytical techniques tailored for Stardust sample analyses. Our report focuses on our systematic disassembly and coordinated analysis of Stardust carrot track #112 from the mm to nm-scale

Coordinated Analysis of Organic Matter in Primitive Meteorites

Carbonaceous chondrites (CC) preserve a diverse range of organic matter formed within cold interstellar environments, the solar nebula, and during subsequent parent body asteroidal processing. This organic matter maintains a unique geochemical and istopic record of organic evolution [1-4]. Bulk studies of organics within CC have revealed a complex array of organic species. However, bulk studies invariably involve solvent extraction, resulting in a loss of spatial context of the host mineral matrix [3, 5]. Correlated in situ chemical and isotopic studies suggest preservation of interstellar organics in the form of spherical, often hollow, micrometer sized organic nano-globules. Nanoglobules often exhibit significant delta 15N and delta D enrichments that imply formation through fractionation of ion-molecule reactions within cold molecular clouds and/or the outer protoplanetary disk [5]. In situ studies such as 6-8 are necessary to understand the organic evolutionary stages of nanoglobules and other components in the nebula and parent body [7]. We carried out coordinated in situ micrometer-scale chemical, mineralogical and isotopic studies of the Murchison (CM2), QUE 99177 (CR3), and Tagish Lake (C2 Ung) CC. These studies were performed using fluorescent microscopy, two-step laser mass spectrometry (microL2MS), NanoSIMS, and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Spectroscopy (EDX). Comparative analysis of three different meteorites will help reveal the effects of parent body processes on the chemistry and isotopic composition of organic matter

Pristine Stratospheric Collections of Cosmic Dust

Since 1981, NASA has routinely collected interplanetary dust particles (IDPs) in the stratosphere by inertial impact onto silicone oil-coated flat plate collectors deployed on the wings of high-altitude aircraft [1]. The highly viscous oil traps and localizes the particles, which can fragment during collection. Particles are removed from the collectors with a micromanipulator and washed of the oil using organic solvents, typically hexane or xylene. While silicone oil is an efficient collection medium, its use is problematic. All IDPs are initially coated with this material (polydimethylsiloxane, n(CH3)2SiO) and traces of oil may remain after cleaning. The solvent rinse itself is also a concern as it likely removes indigenous organics from the particles. To avoid these issues, we used a polyurethane foam substrate for the oil-free stratospheric collection of IDPs

Chemical Evolution of Presolar Organics in Astromaterials

Sub-micron, hollow organic globules reported from several carbonaceous chondrites, interplanetary dust particles, and comet Wild-2 samples returned by NASA?s Stardust mission are enriched in N-15/N-14 and D/H compared with terrestrial materials and the parent materials [1-4]. These anomalies are ascribed to the preservation of presolar cold molecular cloud material from where H, C, and N isotopic constraints point to chemical fractionation near 10 K [5]. An origin well beyond the planet forming region and their survival in meteorites suggests submicrometer organic globules were once prevalent throughout the solar nebula. The survival of the membrane structures indicates primitive meteorites and cometary dust particles would have delivered these organic precursors to the early Earth as well as other planets and satellites. The physical, chemical, and isotopic properties of the organic globules varies to its meteorite types and its lithologies. For example, organic globules in the Tagish Lake meteorite are always embedded in fined grained (poorly crystallized) saponite, and hardly encapsulated in coarse grained serpentine, even though saponite and serpentine are both main components of phyllosilicate matrix of the Tagish Lake meteorite. The organic globules are commonly observed in the carbonate-poor lithology but not in the carbonate-rich one. In Tagish Lake, isolated single globules are common, but in the Bells (CM2) meteorite, globules are mostly aggregated. We will review the evolutions of the organic globules from its birth to alteration in the parent bodies in terms of its own physical and chemical properties as well as its associated minerals

The Spatial Distribution of Organic Matter and Mineralogical Relationships in Carbonaceous Chondrites

Organic matter present within primitive carbonaceous meteorites represents the complex conglomeration of species formed in a variety of physically and temporally distinct environments including circumstellar space, the interstellar medium, the Solar Nebula & Jovian sub-nebulae and asteroids. In each case, multiple chemical pathways would have been available for the synthesis of organic molecules. Consequently these meteorites constitute a unique record of organic chemical evolution in the Universe and one of the biggest challenges in organic cosmochemistry has been in deciphering this record. While bulk chemical analysis has provided a detailed description of the range and diversity of organic species present in carbonaceous chondrites, there is virtually no hard experimental data as to how these species are spatially distributed and their relationship to the host mineral matrix, (with one exception). The distribution of organic phases is nevertheless critical to understanding parent body processes. The CM and CI chondrites all display evidence of low temperature (< 350K) interaction with aqueous fluids, which based on O isotope data, flowed along thermal gradients within the respective parent bodies. This pervasive aqueous alteration may have led to aqueous geochromatographic separation of organics and synthesis of new organics coupled to aqueous mineral alteration. To address such issues we have applied the technique of microprobe two-step laser desorption / photoionization mass spectrometry (L2MS) to map in situ the spatial distribution of a broad range of organic species at the micron scale in the freshly exposed matrices of the Bells, Tagish Lake and Murchison (CM2) carbonaceous chondrites

The Spatial Distribution and Mineralogical Association of Organics in the Tagish Lake and Bells Carbonaceous Chondrites

Chondritic meteorites represent some of the most primitive Solar System materials available for laboratory analysis. While the presence of simple organic molecules has been well documented in such materials [1], little is known about their spatial distribution and to what extent, if any, they exhibit specific mineralogical associations. This dichotomy arises since organic analysis typically involves solvent extraction as a preliminary step. To address these issues we have used two-step laser mass spectrometry (L 2MS) to map in situ the spatial distribution of aromatic and conjugated organics at the micron scale in freshly exposed surfaces of the Tagish Lake and Bells carbonaceous chondrites. Our specific goals are two-fold; firstly to investigate if and how abundance of organic species varies within the meteorite matrix both as an ensemble, and with respect to functional group (e.g., R-OH vs. RCH3) and between members of the same homologous series (e.g., R-H vs. R-(CH2)H). Secondly, to determine whether observed spatial variations can be related to specific mineralogical and/or physical characteristics of the host matrix. In regard to the latter we are particularly interested in the role that carbonaceous nanoglobules [2] play as reservoirs of organic matter. Such globules, which are believed to have formed by photochemical processing of organic-rich ices in the presolar cold molecular cloud or the outermost reaches of the early protosolar disk, are abundant in both the Bells and Tagish Lake chondrites and are noteworthy for having particularly high enrichments in 2H and 15N [3,4]

Coordinated Chemical and Isotopic Imaging of Bells (CM2) Meteorite Matrix

Meteoritic organic matter is a complex conglomeration of species formed in distinct environments and processes in circumstellar space, the interstellar medium, the Solar Nebula and asteroids. Consequently meteorites constitute a unique record of primordial organic chemical evolution. While bulk chemical analysis has provided a detailed description of the range and diversity of organic species present in carbonaceous chondrites, there is little information as to how these species are spatially distributed and their relationship to the host mineral matrix. The distribution of organic phases is nevertheless critical to understanding parent body processes. The CM and CI chondrites all display evidence of low temperature (< 350K) aqueous alteration that may have led to aqueous geochromatographic separation of organics and synthesis of new organics coupled to aqueous mineral alteration. Here we present the results of the first coordinated in situ isotopic and chemical mapping study of the Bells meteorite using a newly developed two-step laser mass spectrometer (mu-L(sup 2)MS) capable of measuring a broad range of organic compounds

Organic Carbon Exists in Mars Meteorites: Where is it on the Martian Surface?

The search for organic carbon on Mars has been a major challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites oil. After the discovery that the SNC meteorites were from Mars, reported C isotopic compositional information which suggested a reduced C component present in the Martian meteorites reported the presence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001. Jull et al. noted in Nakhla there was acid insoluble C component present with more than 75% of its C lacking any C-14, which is modern-day terrestrial carbon. This C fraction was believed to be either indigenous martian or ancient meteoritic carbon. Fisk et al. have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001. Westall et al. have shown the presence of a large irregular fragment of organic material completely embedded within a chip of ALH84001. Interior samples from the Naklnla SNC made available by the British Museum of Natural History, were analyzed. Petrographic examination of Nakhla showed evidence of fractures (approx.0.5 microns wide) filled with dark brown to black dendritic material with characteristics similar to those observed by. Iddingsite is also present along fractures in olivine. Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam microscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry. Observations from the first three techniques are discussed

In Situ Mapping of the Organic Matter in Carbonaceous Chondrites and Mineral Relationships

Carbonaceous chondrite organic matter represents a fossil record of reactions that occurred in a range of physically, spatially and temporally distinct environments, from the interstellar medium to asteroid parent bodies. While bulk chemical analysis has provided a detailed view of the nature and diversity of this organic matter, almost nothing is known about its spatial distribution and mineralogical relationships. Such information is nevertheless critical to deciphering its formation processes and evolutionary history