Engineering topics

Ross, D. K.

Publications and source records attributed to Ross, D. K..

At least 19 records

NASA NTRS2020

Identification of Anomalous Eucrites and Diogenites by Multivariable Discriminant Analysis

Howardite, eucrite and diogenite clan (HED) is the largest magmatic achondrite group and has been suggested to be derived from asteroid (4) Vesta (e.g., [1]). Previous geochemical studies have suggested HEDs were generated by asteroid melting followed by crystallization, metamorphism, and impact [1-6]. However, numerous eucrites and diogenites have anomalous compositional, isotopic or petrological characteristics compared to the norm. This diversity might indicate more complex magma processes on the parent asteroid, or they could be linked to different parental asteroids (e.g., [5]). The former case would imply that the parent asteroid is more heterogenous than currently thought, and that our petrologic models are too simple. The latter case would increase the number of asteroids known to have formed mafic crusts, and would allow for petrological comparisons across numerous bodies. We apply multivariable discrimination analysis (MDA) to a large database of HED pyroxene analyses. This technique allows all elemental information to be considered simultaneously to facilitate identification of groupings, trends, and outliers within the dataset.

Peng, Z. X.↗

NASA NTRS2020

Oxygen Isotopic Imaging of Refractory Inclusions from the Miller Range (MIL) 090019 CO3 Chondrite: A Perovskite Perspective

Calcium-Aluminum-rich Inclusions (CAIs) in primitive meteorites are the first solids to condense in the Solar System. The oxygen isotopic compositions recorded in various mineral components of CAIs provide clues about their origins and post-formation histories, recording processes such as condensation, melting, nebular alteration, and fluidrock reactions on the parent body. MIL 090019 is similar to some rare carbonaceous chondrites such as Acfer 094, DOM 08004/6 and ALH 77303 that contain high abundances of a variety of refractory inclusions. This provides an opportunity to study the oxygen isotopic record of different types of refractory inclusions within the same meteorite. We analyzed CAIs specifically targeting primary minerals that are direct nebular condensates, such as corundum and perovskite, with the goal of gaining insights into the O isotopic composition of the nebular gas(es) from which these CAIs condensed. As MIL 090019 is a classified as CO3.1, it shows some signs of thermal metamorphism, compared to the more primitive CO3 meteorites (e.g., DOM 08004/06). A second goal of this study is to search for evidence of nebular processes in phases such as perovskite and melilite that are susceptible to parent body alteration to varying degrees. We analyzed the oxygen isotopic compositions of various CAIs from the MIL 090019 CO3 carbonaceous chondrite by ion imaging using the NanoSIMS 50L (Nano Secondary Ion Mass Spectrometer) at JSC following methods described in. An advantage of ion imaging over traditional spot analyses is that it provides spatial context to the oxygen isotopic data. This work builds on previously reported oxygen isotopic composition of two other CAIs (CAI-44 and CAI-E2) from the same meteorite thin section.

Mane, P.↗

NASA NTRS2020

Capturing an Evolving Nebular Environment: A Petrographic and Geochemical Study of a Type A, B & C CAI

Calcium, Aluminum-rich Inclusions (CAIs) were the first formed solids in our Solar System, with mineral assemblages reflecting the first phases predicted to condense out of a hot nebular gas of Solar composition. Geochemical, textural and crystallographic information in CAIs can be used to constrain the temperature, pressure, and composition (e.g., oxygen fugacity) of the gaseous reservoir(s) from which they formed, as well as any secondary (nebular and parent body) processes they underwent. Coordinated geochemical and textural analyses provide information on nebular conditions (i.e., astrophysical environments and dynamics of nebular gas reservoirs) in which these CAIs formed. In order to better understand the evolution of nebular reservoirs at the time of CAI formation, we analyzed a Type A, B and C CAI using Electron Probe Micro-Analyzer (EPMA) and Electron BackScatter Diffraction (EBSD) at NASA Johnson Space Center (JSC).

Comins, M. B.↗

NASA NTRS2020

Condensation, Partial Melting and Evaporation Processes Influence the Bulk Compositions of Spinel-Cored Spherules in the CO3.1 Chondrite Miller Range 90019

Here we focus on spinel-cored spherule calcium-aluminum rich inclusions (CAI), dominantly ~75-80 microns in diameter in the CO3.1 chondrite Miller Range 90019, which make up ~ 12 % of the fine-grained CAIs in one thin section. Their mineralogical content ranges from rare grossite- and hibonite-bearing varieties, through perovskite-melilitebearing, to fassaite-bearing and finally anorthitebearing. Non-spherical CAIs have been divided into 4 other groups, defined based on mineralogical abundances. We also characterized a group of AOAs from this sample. No glass has been recognized in any inclusions. Some relatively evolved members (anorthite-, spinel- + fassaite-bearing) among the spherules are found engulfed in AOAs. We characterized the bulk compositions of ~145 CAIs and AOAs in this meteorite, derived from EDS-x-ray mapping of the inclusions. We determined bulk compositions both with and without Wark-Lovering rims (when present), which are largely composed of diopside  forsterite. The balance of the inclusions appear to have not been melted or partially melted, but rather they have textures that indicate they are condensates, often modified by extensive reaction with nebular gases. This presents the opportunity to examine effects on the bulk compositions of spherules resulting potentially from melting plus evaporation. Other aspects of this suite of refractory inclusions have been discussed in these abstracts. Oxygen isotope variations in one spherule were presented in [4]. The latter study showed a complex history of reaction with nebular gases possessing a variety of Oisotope compositions. Additional O isotopic studies of inclusions in this work are included in Mane et al.

Ross, D. K.↗

NASA NTRS2019

Analysis of WFPC-2 Core Samples for MMOD Discrimination

An examination of the Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC-2) radiator assembly was conducted at NASA Goddard Space Flight Center during the summer of 2009. Immediately apparent was the predominance of impact features, identified as simple or complex craters, resident only in the thermal paint layer; similar features were observed during a prior survey of the WFPC-1 radiator. Larger impact features displayed spallation zones, darkened areas, and other features not observed in impacts onto bare surfaces. Craters were extracted by coring the radiator in the NASA Johnson Space Center’s Space Exposed Hardware cleanroom and were subsequently examined using scanning electron microscopy/energy dispersive X-ray spectroscopy to determine the likely origin, e.g., micrometeoritic or orbital debris, of the impacting projectile. Recently, a selection of large cores was re-examined using a new technique developed to overcome some limitations of traditional crater imaging and analysis. This technique, motivated by thin section analysis, examines a polished, lateral surface area revealed by cross-sectioning the core sample. This paper reviews the technique, the classification rubric as extended by this technique, and results to date.

Anz-Meador, P.↗

NASA NTRS2019

Electron Beam Damage in Apatite: Limitations for SKα Measurements of S6+/∑S

In magmatic systems, the availabil- ity of excess oxygen that can react with multivalent elements such as Fe and S to change their charge (oxi- dation of Fe2+ to Fe3+ or reduction of S6+ to S2-) is characterized by a parameter called the oxygen fugacity (ƒO2). The ƒO2 controls the availability of these ions and consequently the minerals—and the chemistry of those minerals—that crystallize from a melt. Mineral mode and chemistry control how magmas evolve, and given that ƒO2 varies by many orders of magnitude on different planets [2], understanding the ƒO2 of a mag- ma is critical to relating observations about a magma to the body on which it forms. The mineral apatite was long thought to only incor- porate S6+ in a coupled substitution for P5+, but recently natural apatites with S2- were identified in lunar mare basalts that crystallized at low ƒO2 [3]. This suggests that apatite can be used as a monitor of ƒO2 assuming that one can 1) measure S6+/∑S (S6+ over total sulfur), and 2) determine some partitioning relationship be- tween apatite and melt for S6+ and S2-. The most common method for measuring S6+/∑S is X-ray Absorption Near-Edge Spectroscopy (XANES), but given the limited access to synchrotron facilities, it is wise to explore the potential of other methods for measuring S6+/∑S. One such possible method relies upon the shift in energy of the sulfur K-α peak on the electron microprobe. However, apatite is subject to well-documented beam damage [4, 5], so it is neces- sary to evaluate under what conditions can reliable S6+ ethod.

de Chizelle, J. Kuhn↗

NASA NTRS2019

Acid-Sulfate Weathering Environment at Shergottite Provenance on Mars

In some impact melt (IM) glasses in the shergottites such as EET79001, Shergotty and Tissint, recently showed that secondary mineral assemblages having large sulfur excesses cannot be produced in-situ by impact shock melting of the host rock constituents. Instead, these putative secondary minerals inferred to be present in IM glasses were produced somewhere else in the shergottite source region and were subsequently mobilized into the host rock voids (by lava erosion or aolian activity) prior to impact ejection. In this abstract, we examine the aqueous conditions (pH and water/rock ratios) under which the acid sulfate solutions could have interacted with the primary minerals in the basaltic rocks and precipitated the secondary minerals such as Fe-sulfates in some cases and Ca- and Al-sulfates in other cases under favorable conditions at the shergottite provenance on Mars.

Rao, M. N.↗

NASA NTRS2019

Elemental Variation and Petrogenesis of Pyroxenes in HED Meteorites by Multivariable Discriminant Analysis Method

HED (Howardite, Eucrite and Diogenite) are meteorites with mafic and ultramafic igneous composition. Previous studies suggested HED came from asteroid (4) Vesta and they were generated by magmatic melting followed by differentiation crystallization, metamorphic, and impact. Uniform oxygen isotopic composition of HED samples favors global magma ocean for (4) Vesta. However, the petrological diversity of HED may indicate more complex magma processes in the meteorites. In general, most of the geochemical studies are using traditional methods (e.g. element to element or ratio to ratio plots) to classify the different rock type and groups. With the traditional methods, only limited elements can be shown in a figure. As such, some meteorites may have been identified as HED by a traditional method but found different either in isotopic composition or other elemental characteristic. These anomalous HED meteorites may or may not come from asteroid (4) Vesta. In fact, magma is a unit system where any elemental change should affect to all other elements as a whole, it would be reasonable to consider all elements together to look for the systematical changes. Using multivariable discriminant analysis (MDA) method is one of such testing for their geochemical variation. The method may be able to help us to better understand the petrologic processes and the relationship among elements. This study is to test the MDA method by focus mainly on pyroxene composition of eucrite and diogenite.

Peng, Z. X.↗

NASA NTRS2018

Outer Solar System Material in Inner Solar System Regolith Breccias

There is excellent evidence that a dynamical instability in the early solar system led to gravitational interactions between the giant planets and trans-Neptunian objects (TNOs). Giant planetary migration triggered by the instability dispersed a disk of primordial TNOs and created a number of small body reservoirs (e.g. the Kuiper Belt, scattered disk, irregular satellites, and the Jupiter/Neptune Trojan populations). It also injected numerous bodies into the main asteroid belt, where modeling shows they can successfully reproduce the observed P and D-type asteroid populations. During the injection era and after implantation, some of these “main belt TNOs” would have collided with S-class asteroids. Some of this material may have survived as a component of asteroid regolith breccias. Thus, we have been searching for evidence of these impact events in the form of carbonaceous xenoliths in brecciated ordinary chondrites. These xenoliths would have experienced a wide range of impact velocities, and therefore we should expect to see everything between relatively unaltered material to completely shock-melted lithologies. This material might also be different from the carbonaceous chondrites that represent standard C-complex asteroids. A goal of this research is to define useful criteria for distinguishing between these two classes of materials, including O, Cr, N and C isotopes, petrographic characteristics, and chronology.

Zolensky, M.↗

NASA NTRS2018

Effect of Silicon on Activity Coefficients of P, Bi, Cd, Sn, and Ag in Liquid Fe-Si, and Implications for Core Formation

Cores of differentiated bodies (Earth, Mars, Mercury, Moon, Vesta) contain light elements such as S, C, Si, and O. We have previously measured small effects of Si on Ni and Co, and larger effects on Mo, Ge, Sb, As metal/silicate partitioning. The effect of Si on metal-silicate partitioning has been quantified for many siderophile elements, but there are a few key elements for which the effects are not yet quantified. Here we report new experiments designed to quantify the effect of Si on the partitioning of Bi, Cd, Sn, Ag, and P between metal and silicate melt. The results will be applied to Earth, Mars, Moon, and Vesta, for which we have good constraints on the mantle Bi, Cd, Sn, Ag, and P concentrations from mantle and/or basalt samples.

Righter, K.↗

NASA NTRS2018

The Almahata Sitta Polymict Ureilite from the University of Khartoum Collection: Classification, Distribution of Clast Types in the Strewn Field, New Meteorite Types, and Implications for the Structure of Asteroid 2008 TC3

The Almahata Sitta (AhS) polymict ureilite fell in 2008 when asteroid 2008 TC3 impacted over Sudan]. It is the first meteorite to originate from an asteroid that had been tracked and studied in space (with spectral classification) before impact, and provides a unique opportunity to correlate properties of meteorites with those of their parent asteroid. More than 700 monolithologic stones from the AhS fall were collected. Of those previously studied, approx. 70% were ureilites and approx. 30% were chondrites. It has been inferred that 2008 TC3 was loosely aggregated and porous and disintegrated in the atmosphere, with only its most coherent clasts falling as stones. However, understanding the structure of this asteroid is limited by incomplete study of the heterogeneous stones, and the loss of most of the mass of the asteroid. The University of Khartoum (UOK) AhS collection contains over >600 AhS stones with find coordinates. We are studying this collection to determine: 1) the proportion of ureilitic to various non-ureilitic stones; 2) the distribution of types of stones in the strewn field; and 3) the compositional and physical structure of 2008 TC3. We report on 61 new stones, including a unique sample that may represent the bulk of the material lost from 2008 TC3.

Goodrich, C. A.↗

NASA NTRS2017

Oxygen Buffering in High Pressure Solid Media Assemblies: New Approach Enabling Study of fO2 from IW-4 to IW+4.5

Oxygen fugacity is an intensive parameter that controls some fundamental chemical and physical properties in planetary materials. In terrestrial magmas high fO2 promotes magnetite stability and low fO2 causes Fe-enrichment due to magnetite suppression. In lunar and asteroidal basalts, low fO2 can allow metal to be stable. Experimental studies will therefore be most useful if they are done at a specific and relevant fO2 for the samples under consideration. Control of fO2 in the solid media apparatus (piston cylinder multi-anvil) has relied on either sliding sensors or graphite capsule buffering, which are of limited application to the wide range of fO2 recorded in planetary or astromaterials. Here we describe a new approach that allows fO2 to be specified across a wide range of values relevant to natural samples.

Righter, K.↗

NASA NTRS2017

Multiple Nebular Gas Reservoirs Recorded by Oxygen Isotope Variation in a Spinel-rich CAI in CO3 MIL 090019

We conducted NanoSIMS O-isotopic imaging of a primitive spinel-rich CAI spherule (27-2) from the MIL 090019 CO3 chondrite. Inclusions such as 27-2 are proposed to record inner nebula processes during an epoch of rapid solar nebula evolution. Mineralogical and textural analyses suggest that this CAI formed by high temperature reactions, partial melting, and condensation. This CAI exhibits radial O-isotopic heterogeneity among multiple occurrences of the same mineral, reflecting interactions with distinct nebular O-isotopic reservoirs.

Simon, J. I.↗

NASA NTRS2017

NWA10758: A New CV3 Chondrite Bearing a Giant CAI with Hibonite-Rich Wark-Lovering Rim

Northwest Africa (NWA) 10758 is a newly identified carbonaceous chondrite that is a Bali-like oxidized CV3. The large Ca-Al rich inclusion (CAI) in this sample is approx. 2.4 x 1.4 cm. The CAI is transitional in composition between type A and type B, with interior mineralogy dominated by melilite, plus less abundant spinel and Al-Ti rich diopside, and only very minor anorthite (Fig. 1A). This CAI is largely free of secondary alteration in the exposed section we examined, with almost no nepheline, sodalite or Ca-Fe silicates. The Wark-Lovering (WL) rim on this CAI is dominated by hibonite, with lower abundances of spinel and perovskite, and with hibonite locally overlain by melilite plus perovskite (as in Fig. 1B). Note that the example shown in 1B is exceptional. Around most of the CAI, hibonite + spinel + perovskite form the WL rim, without overlying melilite. The WL rim can be unusually thick, ranging from approx. 20 microns up to approx. 150 microns. A well-developed, stratified accretionary rim infills embayments of the CAI, and thins over protuberances in the convoluted CAI surface.

Ross, D. K.↗

NASA NTRS2017

Northwest Africa 10758: A New CV3 Chondrite Bearing a Giant CAI with Hibonite-Rich Wark-Lovering Rim

Northwest Africa (NWA) 10758 is a newly identified carbonaceous chondrite that is a Bali-like oxidized CV3. The large Ca-Al rich inclusion (CAI) in this sample is approx. 2.4 x 1.4 cm. The CAI is transitional in composition between type A and type B, with interior mineralogy dominated by melilite, plus less abundant spinel and Al-Ti rich diopside, and only very minor anorthite (Fig. 1A). This CAI is largely free of secondary alteration in the exposed section we examined, with almost no nepheline, sodalite or Ca-Fe silicates. The Wark-Lovering (WL) rim on this CAI is dominated by hibonite, with lower abundances of spinel and perovskite, and with hibonite locally overlain by melilite plus perovskite (as in Fig. 1B). Note that the example shown in 1B is exceptional. Around most of the CAI, hibonite + spinel + perovskite form the WL rim, without overlying melilite. The WL rim can be unusually thick, ranging from approx.20 microns up to approx. 150 microns. A well-developed, stratified accretionary rim infills embayments of the CAI, and thins over protuberances in the convoluted CAI surface.

Ross, D. K.↗

NASA NTRS2017

Effect of Silicon on Activity Coefficients of P, Bl, CD, SN, and AG in Liquid Fe-Si, and Implications for Differentiation and Core Formation

Cores of differentiated bodies (Earth, Mars, Mercury, Moon, Vesta) contain light elements such as S, C, Si, and O. We have previously measured small effects of Si on metal-silicate partitioning of Ni and Co [1,2], and larger effects for Mo, Ge, Sb, As [2]. The effect of Si on many siderophile elements could be an important, and as yet unquantified, influence on the core-mantle partitioning of SE. Here we report new experiments designed to quantify the effect of Si on the partitioning of Bi, Cd, Sn, Ag, and P between metal and silicate melt. The results will be applied to Earth, Mars, Mercury, Moon, and Vesta, for which we have excellent constraints on the mantle Bi, Cd, Sn, Ag, and P concentrations from mantle and/or basalt samples.

Righter, K.↗

NASA NTRS2017

Evolved-Lithology Clasts in Lunar Breccias: Relating Petrogenetic Diversity to Measured Water Content

Studies of the inventory and distribution of water in lunar rocks have recently begun to focus on alkali suite samples as possible water repositories, particularly the most highly evolved granitoid lithologies. Although H analyses of feldspars in these rocks have so far pointed to 'low' (less than 20 ppm) H2O contents, there is sufficient variability in the dataset (e.g., 2-20 ppm) to warrant consideration of the petrogenetic factors that may have caused some granitoid-to-intermediate rocks to be dryer or wetter than others. Given that all examples of these rocks occur as clasts in complex impact breccias, the role of impact and other factors in altering water contents established by primary igneous processes becomes a major factor. We are supporting our ongoing SIMS studies of water in evolved lunar lithologies with systematic SEM and EPMA observations. Here we report a synthesis of the observations as part of developing discriminating factors for reconstructing the thermal, crystallization and shock history of these samples as compared with their water contents.

Christoffersen, R.↗

NASA NTRS2017

Examination of Multiple Lithologies Within the Primitive Ordinary Chondrite NWA 5717

Northwest Africa 5717 is a primitive (subtype 3.05) ungrouped ordinary chondrite which contains two apparently distinct lithologies. In large cut meteorite slabs, the darker of these, lithology A, looks to host the second, much lighter in color, lithology B (upper left, Fig. 1). The nature of the boundary between the two is uncertain, ranging from abrupt to gradational and not always following particle boundaries. The distinction between the lithologies, beyond the obvious color differences, has been supported by a discrepancy in oxygen isotopes and an incongruity in the magnesium contents of chondrule olivine. Here, quantitative textural analysis and mineralogical methods have been used to investigate the two apparent lithologies within NWA 5717. Olivine grains contained in a thin section from NWA 7402, thought to be paired to 5717, were also measured to re-examine the distinct compositional range among the light and dark areas. Procedure: Particles from a high-resolution mosaic image of a roughly 13x15cm slice of NWA 5717 were traced in Adobe Photoshop. Due to the large size of the sample, visually representative regions of each lithology were chosen to be analyzed. The resulting layers of digitized particles were imported into ImageJ, which was used to measure their area, along with the axes, the angle from horizontal, and the centroid coordinates of ellipses fitted to each particle following the approach. Resulting 2D pixel areas were converted to spherical diameters employing the unfolding algorithm, which outputs a 3D particle size distribution based on digitized 2D size frequency data. Spatstat was used to create kernel density plots of the centroid coordinates for each region. X-ray compositional maps, microprobe analyses, and Mossbauer spectroscopy was conducted on a thin section of NWA 7402, tentatively paired to NWA 5717.

Cato, M. J.↗