Engineering topics

Flynn, G. J.

Publications and source records attributed to Flynn, G. J..

At least 19 records

NASA NTRS2019

A Kuiper Belt Source for Solar Flare Track-Rich Interplanetary Dust Particles

The presence of solar flare particle tracks in mineral grains within interplanetary dust particles (IDPs) has long been accepted as proof of their extraterrestrial origin [e.g. 1]. The 10-20 micrometers diameter IDPs released by dust producing objects in the solar system (mainly comets and asteroids) spiral in towards the Sun under the influence of Poynting-Robertson (PR) drag forces [2] and accumulate solar flare energetic particle tracks during their journey. The number of IDPs with well-constrained track density measurements is small, owing to the difficulty in the measurements and the lack of appropriatelysized crystals in which to image them. In order to use track densities as a chronometer of space exposure, the track production rate must be known. All previous work relied on track production rates determined by chemical etching techniques [e.g. 3], but tracks in IDPs are measured using TEM imaging. Here we report measurements of track densities in IDPs from both the anhydrous and hydrated IDP groups. Using the track production calibration determined from TEM observations of anorthite and olivine in lunar rock 64455 [4] we estimate space exposure times for these IDPs to constrain their parent body sources.

Keller, L. P.↗

NASA NTRS2014

Comparison of Nickel XANES Spectra and Elemental Maps from a Ureilite, a LL3.8 Ordinary Chondrite, Two Carbonaceous Chondrites and Two Large Cluster IDPs

Nickel in the extraterrestrial world is commonly found in both Fe-Ni sulfide and Fe-Ni met-al forms [1] and in the pure metal state in the interior of iron meteorites where it is not easily oxidized. Ni is also found in olivine, pyroxene and glasses and in some melts the partitioning of Ni between the olivines and glass is controlled by the amount of S in the melt [2]. Its most common valence state is Ni(2+) but Ni also occurs as Ni(0), Ni(+), and Ni(3+) and rarely as Ni(2-), Ni(1-) and Ni(4+) [3]. It's valence state in olivines is Ni(2+) in octa-hedral coordination on the M1 site and rarely on the M2 site.[4]. The chemical sensitivity of X-ray absorp-tion near-edge structure (XANES) spectroscopy is well established and can be used to determine not only va-lence states but also coordination sites [5]. We report here Ni XANES spectroscopy and elemental maps collected from 2 carbonaceous chondrites, 2 large clus-ter IDPs, 1 ureilite and 1 LL3 orginary chondrite.Using XANES it may be possible to find a common trait in the large cluster IDPs that will also be found in mete-orite samples.

Wirick, S.↗

NASA NTRS2013

C/N and other Elemental Ratios of Chondritic Porous IDPS and a Fluffy Concordia Micrometeorite

Chondritic porous interplanetary dust particles (CP-IDPs) may be cometary in origin [1], as may ultracarbona-ceous (UCAMMs) [2] and 'fluffy' [3] micrometeorites from the Concordia collection. They are all rich in organics, which can rim grains and may have helped glue grains together during accretion [4]. The organics also contain nitrogen the input of which to Earth has potential biological importance. We report C/N ratios, and other properties of CP-IDPs and a Concordia fluffy microme-teorite.

Smith, T.↗

NASA NTRS2013

Mid-Infrared Study of Samples from Multiple Stones from the Sutters Mill Meteorite

The Sutter's Mill meteorite fell in N. California on April 22, 2012 and numerous pieces have been recovered and studied. We present Fourier transform infrared (FTIR) spectra of fragments from several stones of the meteorite. Methods and analysis: Infrared spectra of the samples were recorded with a Nicolet iN10 MX FTIR microscope in the mid-IR range (4000-675/cm; spectral resolution 4/cm). All samples were deposited on a clean glass slide, crushed with a stainless steel roller tool, and placed directly on the focal plane of the microscope. IR spectra were collected by averaging 128 scans. Results: Preliminary IR spectra of the non-fusion crust samples show mineral compositions that are dominated by phyllosilicates, carbonates, or mixtures of both [2]. The carbonates display a dominant, broad band centered at 1433/cm, with additional bands at 2515/cm, 1797/cm, 882/cm, and 715/cm). Features associated with phyllosilicates include a symmetric Si-O stretching mode band centered at 1011/cm and several O-H stretching mode bands. The O-H shows up in two forms (1) a broadband centered at 3415/cm that is probably largely due to adsorbed H2O and (2) a much weaker, narrower feature centered near 3680/cm due to structural -OH. Features observed in the 2985-2855/cm range suggest the presence of aliphatic -CH3 and -CH2- groups. The relative intensities of the bands in this range are somewhat unusual. Typically, the asymmetric aliphatic CH stretching bands are stronger than the symmetric stretching bands, but in this case the reverse is true. This unusual pattern is well matched by the aliphatic features seen in the spectrum of a terrestrial calcite (CaCO3) standard. This observation, and the fact that the strength of the carbonate and aliphatic bands seem to correlate, suggest the organics are associated with the carbonates. Conclusions: IR spectra of samples from the Sutter's Mill meteorite show absorption features associated with carbonates, phyllosilicates, and organics. Both the unusual band profile of the aliphatic C-H stretching mode bands and their correlation with the strength of the carbonate bands suggests the organics and the carbonates are associated in some manner.

Sutter's mill↗

NASA NTRS2013

Chemical Heterogeneity of a Large Cluster IDP: Clues to its Formation History Using X-ray Fluorescence Mapping and XANES Spectroscopy

Chondritic porous IDPs may be among the most primitive objects found in our solar system [1]. They consist of many micron to submicron minerals, glasses and carbonaceous matter [2,3,4,5,6,7] with > 10(exp 4) grains in a 10 micron cluster [8]. Speculation on the environment where these fine grained, porous IDPs formed varies with possible sources being presolar dusty plasma clouds, protostellar condensation, solar asteroids or comets [4,6,9]. Also, fine grained dust forms in our solar system today [10,11]. Isotopic anomalies in some particles in IDPs suggest an interstellar source[4,7,12]. IDPs contain relic particles left from the dusty plasma that existed before the protostellar disk formed and other grains in the IDPs formed later after the cold dense nebula cloud collapsed to form our protostar and other grains formed more recently. Fe and CR XANES spectroscopy is used here to investigate the oxygen environment in a large (>50 10 micron or larger sub-units) IDP. Conclusions: Analyzing large (>50 10 micron or larger sub-units) CP IDPs gives one a view on the environments where these fine dust grains formed which is different from that found by only analyzing the small, 10 micron IDPs. As with cluster IDP L2008#5 [3], L2009R2 cluster #13 appears to be an aggregate of grains that sample a diversity of solar and perhaps presolar environments. Sub-micron, grain by grain measurement of trace element contents and elemental oxidation states determined by XANES spectroscopy offers the possibility of understanding the environments in which these grains formed when compared to standard spectra. By comparing thermodynamic modeling of condensates with analytical data an understanding of transport mechanisms operating in the early solar system may be attained.

Wirick, S.↗

NASA NTRS2012

Coordinated Analyses of Mineral-organic Matter Associations in Interplanetary Dust Particles

Little is known about the timing and processes involved in the incorporation of organic matter with inorganic materials in early Solar System bodies. Recently, X-ray absorption near-edge spectroscopy (XANES) studies showed carbon-rich rims surrounding individual mineral grains in anhydrous IDPs [1,2]. These carbonaceous rims are believed to have formed prior to parent body formation and likely served to bond mineral grains during accretion into larger aggregates. We are exploring the nature of these carbonaceous rims through coordinated analyses of their chemistry, mineralogy, spectroscopy and isotopic characteristics. Here we report our preliminary mineralogical observations.

Nakamura-Messenger, K.↗

NASA NTRS2012

Characterization of 81P/Wild 2 Particles C2067,1,111,6.0 and C2067,1,111,8.0

The concentrations of C and N in cometary particles are of interest in characterizing the regions where comets formed. One aim of this work is to analyze enough Stardust particles to draw meaningful statistical conclusions about their inventories of C and N. Toward that end we report recent studies of Stardust particles and related materials.

Smith, T.↗

NASA NTRS2011

Soft X-Ray Photoionizing Organic Matter from Comet Wild 2: Evidence for the Production of Organic Matter by Impact Processes

The Stardust mission collected both mineral and organic matter from Comet Wild 2 [1,2,3,4]. The organic matter discovered in Comet Wild 2 ranges from aromatic hydrocarbons to simple aliphatic chains and is as diverse and complex as organic matter found in carbonaceous chondrites and interplanetary dust particles.[3,5,6,7,8,9]. Compared to insoluble organic matter from carbonaceous chondrites the organic matter in Comet Wild 2 more closely resembles organic matter found in the IDPS both hydrous and anhydrous. Common processes for the formation of organic matter in space include: Fischer-Tropsch, included with this aqueous large body and moderate heating alterations; UV irradiation of ices; and; plasma formation and collisions. The Fischer-Tropsch could only occur on large bodies processes, and the production of organic matter by UV radiation is limited by the penetration depth of UV photons, on the order of a few microns or less for most organic matter, so once organic matter coats the ices it is formed from, the organic production process would stop. Also, the organic matter formed by UV irradiation would, by the nature of the process, be in-sensitive to photodissocation from UV light. The energy of soft X-rays, 280-300 eV occur within the range of extreme ultraviolet photons. During the preliminary examination period we found a particle that nearly completely photoionized when exposed to photons in the energy range 280-310eV. This particle experienced a long exposure time to the soft x-ray beam which caused almost complete mass loss so little chemical information was obtain. During the analysis of our second allocation we have discovered another particle that photoionized at these energies but the exposure time was limited and more chemical information was obtained.

Zolensky, Michael E.↗

NASA NTRS2011

Stardust Interstellar Foils I1061N,1 and I1031N, 1: First Results from Automated Crater Searches and Future Analytical Possibilities

In addition to samples from comet 81P/Wild 2, NASA's Stardust mission may have returned the first samples of contemporary interstellar dust. The interstellar tray collected particles for 229 days during two exposures prior to the spacecraft encounter with Wild 2 and tracked the interstellar dust stream for all but 34 days of that time. In addition to aerogel capture cells, the tray contains Al foils that make up approx.15% of the total exposed collection surface . Interstellar dust fluxes are poorly constrained, but suggest that on the order of 12-15 particles may have impacted the total exposed foil area of 15,300 sq mm; 2/3 of these are estimated to be less than approx.1 micrometer in size . Examination of the interstellar foils to locate the small rare craters expected from these impacts is proceeding under the auspices of the Stardust Interstellar Preliminary Examination (ISPE) plan. Below we outline the automated high-resolution imaging protocol we have established for this work and report results obtained from two interstellar foils.

Zolensky, M. E.↗

NASA NTRS2011

Identification of Impact Craters in Foils from the Stardust Interstellar Dust Collector

The Stardust Interstellar Dust Collection tray provides the first opportunity for the direct laboratory-based measurement of contemporary interstellar dust. The total exposed surface of the tray was approximately 0.1 square meters, including 153 square centimeters of Al foil in addition to the silica aerogel tiles that are the primary collection medium. Preliminary examination of aerogel tiles has already revealed 16 tracks from particle impacts with an orientation consistent with an interstellar origin, and to date four of the particles associated with these tracks have a composition consistent with an extraterrestrial origin. Tentative identification of impact craters on three foil samples was also reported previously. Here we present the definitive identification of 20 impact craters on five foils.

Stroud, R. M.↗

NASA NTRS2011

A New View on Interstellar Dust - High Fidelity Studies of Interstellar Dust Analogue Tracks in Stardust Flight Spare Aerogel

In 2000 and 2002 the Stardust Mission exposed aerogel collector panels for a total of about 200 days to the stream of interstellar grains sweeping through the solar system. The material was brought back to Earth in 2006. The goal of this work is the laboratory calibration of the collection process by shooting high speed [5 - 30km/s] interstellar dust (ISD) analogues onto Stardust aerogel flight spares. This enables an investigation into both the morphology of impact tracks as well as any structural and chemical modification of projectile and collector material. First results indicate a different ISD flux than previously assumed for the Stardust collection period.

Zolensky, Michael E.↗

NASA NTRS2011

FTIR Analysis of Aerogel Keystones from the Stardust Interstellar Dust Collector: Assessment of Terrestrial Organic Contamination and X-Ray Microprobe Beam Damage

The Stardust Interstellar Dust Collector (SIDC) was intended to capture and return contemporary interstellar dust. The approx.0.1 sq m collector was composed of aerogel tiles (85% of the collecting area) and aluminum foils and was exposed to the interstellar dust stream for a total exposure factor of 20 sq m day. The Stardust Interstellar Preliminary Examination (ISPE) is a consortium-based project to characterize the collection using nondestructive techniques. Sandford et al. recently assessed numerous potential sources of organic contaminants in the Stardust cometary collector. These contaminants could greatly complicate the analysis and interperetation of any organics associated with interstellar dust, particularly because signals from these particles are expected to be exceedingly small. Here, we present a summary of FTIR analyses of over 20 aerogel keystones, many of which contained candidates for interstellar dust.

Zolensky, M. E.↗

NASA NTRS2011

Four Interstellar Dust Candidates from the Stardust Interstellar Dust Collector

In January 2006, the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, Comet 81P/Wild2, and a collector dedicated to the capture and return of contemporary interstellar dust. Both collectors were approx. 0.1 sq m in area and were composed of aerogel tiles (85% of the collecting area) and aluminum foils. The Stardust Interstellar Dust Collector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 sq m/day. The Stardust Interstellar Preliminary Examination (ISPE) is a consortium-based project to characterize the collection using nondestructive techniques. The goals and restrictions of the ISPE are described . A summary of analytical techniques is described.

Westphal, A. J.↗

NASA NTRS2010

Analysis of "Midnight" Tracks in the Stardust Interstellar Dust Collector: Possible Discovery of a Contemporary Interstellar Dust Grain

In January 2006, the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, Comet 81P/Wild2, and a collector dedicated to the capture and return of contemporary interstellar dust. Both collectors were approximately 0.1m(exp 2) in area and were composed of aerogel tiles (85% of the collecting area) and aluminum foils. The Stardust Interstellar Dust Collector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 m(exp 2) day. The Stardust Interstellar Preliminary Examination (ISPE) is a three-year effort to characterize the collection using nondestructive techniques.

Westphal, A. J.↗

NASA NTRS2009

Carbon XANES Data from Six Aerogel Picokeystones Cut from the Top and Bottom Sides of the Stardust Comet Sample Tray

Great care and a large effort was made to minimize the amount of organic matter contained within the flight aerogel used to collect Comet 81P/Wild 2 samples. Even so, by the very nature of the production process and silica aerogel s affinity for volatile organics keeping silica aerogel free from organics is a monumental task. Silica aerogel from three production batches was flown on the Stardust sample return mission. All 3 types had layered densities varying from 5mg/ml to 50 mg/ml where the densest aerogel was farthest away from the collection area. A 2 step gelation process was used to make the flight aerogel and organics used in this process were tetraethylorthosilicate, ethanol and acetonitrile. Both ammonium hydroxide and nitric acid were also used in the aerogel production process. The flight aerogel was baked at JPL at 300 C for 72 hours, most of the baking was done at atmosphere but twice a day the oven was pumped to 10 torr for hour [1]. After the aerogel was baked it was stored in a nitrogen purged cabinet until flight time. One aerogel cell was located in the SRC away from any sample collection area as a witness to possible contamination from out gassing of the space craft, re-entry gases and any other organic encounter. This aerogel was aerogel used in the interstellar collection sample tray and is the least dense of the 3 batches of aerogel flown. Organics found in the witness tile include organics containing Si-CH3 bonds, amines and PAHS. Besides organic contamination, hot spots of calcium were reported in the flight aerogel. Carbonates have been detected in comet 81P/Wild2 samples . During preflight analyses, no technique was used to analyze for carbonates in aerogel. To determine if the carbonates found in 81P/Wild2 samples were from the comet, it is necessary to analyze the flight aerogel for carbonate as well as for organics.

Wirick, S.↗

NASA NTRS2009

Evidence for Changes in 81PIWild 2 Organic Matter Since Collection and Comparison of 82PIWild 2 and IDP Organic Matter to Access the Thermal Effects of Aerogel Capture

NASA s Stardust spacecraft collected cometary material during its passage through the dust coma of comet 81P/Wild 2 on January 2nd, 2004 and delivered this material to Earth on January 15th 2006. The first fragment we analyzed during the preliminary examination was partially vaporized by the X-ray beam. The carbonaceous material that survived was re-analysis approx.2 months later and the carbon spectrum for this material had significantly changed from what we first observed.. We have observed similar changes to the carbonaceous matter in some interplanetary dust particles ( IDPs). Some of the 81P/Wild 2 organic matter volatilized upon impact with the aerogel as observed using IR spectroscopy where IR spectra were collected several mms away from sample tracks [1]. The time-temperature profile experienced by any particular 81P/Wild 2 grain during aerogel capture is not known, although Brownlee, et al. suggest that fine-grained materials, <1 micron in size, fragmented and then partially vaporized during collection, while particles much larger then 1 micron in size were captured intact [2]. Nearly all organic matter is subject to thermal alteration. To assess the heating and alteration experienced by the 81P/Wild 2 organic matter during capture we are comparing 81P/Wild2 organic matter with IDP organic matter where we have evidence of heating in the IDP [3,4].

Wirick, S.↗

NASA NTRS2008

Carbonate in Comets: A Comparison of Comets 1P/Halley, 9P/Temple 1, and 81P/Wild 2

Comets are generally believed to have formed in a cold region, trapping in the cometary ices the original low-temperature condensate grains of our Solar System. These grains would have been preserved in cold-storage, at a temperature below the freezing point of CO2, for the last 4.5+ billion years. Carbonates are common in hydrous meteorites and hydrous interplanetary dust particles (IDPs), where they are believed to have formed by parent-body aqueous processing. Since simple models of cometary evolution involve no aqueous processing, carbonates were generally presumed not to occur in comets. However, Toppani et al. [1] have performed experiments that indicate carbonate can be formed by non-equilibrium condensation in circumstellar environments where water is present as a vapor, not as a liquid. This suggests carbonate might have condensed in cold regions of the Solar Nebula, and might be present in comets.

Flynn, G. J.↗

NASA NTRS2008

Comparison of Carbon XANES Spectra from an Iron Sulfide from Comet Wild 2 with an Iron Sulfide Interplanetary Dust Particle

Among one of the first particles removed from the aerogel collector from the Stardust sample return mission was an approx. 5 micron sized iron sulfide. The majority of the spectra from 5 different sections of this particle suggests the presence of aliphatic compounds. Due to the heat of capture in the aerogel we initially assumed these aliphatic compounds were not cometary but after comparing these results to a heated iron sulfide interplanetary dust particle (IDP) we believe our initial interpretation of these spectra was not correct. It has been suggested that ice coating on iron sulfides leads to aqueous alteration in IDP clusters which can then lead to the formation of complex organic compounds from unprocessed organics in the IDPs similar to unprocessed organics found in comets [1]. Iron sulfides have been demonstrated to not only transform halogenated aliphatic hydrocarbons but also enhance the bonding of rubber to steel [2,3]. Bromfield and Coville (1997) demonstrated using Xray photoelectron spectroscopy that "the surface enhancement of segregated sulfur to the surface of sulfided precipitated iron catalysts facilitates the formation of a low-dimensional structure of extraordinary properties" [4]. It may be that the iron sulfide acts in some way to protect aliphatic compounds from alteration due to heat.

Wirick, S.↗