Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “HED”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Dawn and the Vesta-HED Connection

Although it is difficult to explain exactly how eucrites and diogenites are related through simple magmatic processes, their shared oxygen isotopic compositions and the common occurrence of clasts of both lithologies in howardite breccias support derivation from a common parent body. For decades, HED meteorites have been linked to asteroid 4 Vesta, based on spectral similarities [1] and the discovery of a dynamical family (Vestoids) that provides a bridge between Vesta and nearby resonance escape hatches [2]. Although recently derived constraints on the rapidity of HED parent body differentiation, based on measurements of Al-26 in diogenites, have been used to argue against the Vesta-HED connection [3], new thermal evolution models [e.g., 4] appear to be heated and melted fast enough to account for this constraint. Data from the Dawn orbiter strengthen the Vesta - HED linkage and provide new insights into petrogenetic interpretations of these meteorites.

McSween, H. Y.↗
NASA NTRS2016

The Diversity of Anomalous HEDs: Isotopic Constraints on the Connection of EET 92023, GRA 98098, and Dhofar 700 With Vesta

The possibility for multiple parent bodies, instead of a common parent body of Vesta, for eucrites has been suggested based on the variable oxygen isotopic composition observed in some eucrites.. Recently, we added an extra dimension to the discussion based on the (epsilon)54Cr composition of the same eucrites with known (delta)17O to compare with the normal eucrites. The combined (delta)17O and (epsilon)54Cr isotope systematics for Pasamonte, PCA 91007, A-881394, and Ibitira indicate their likely origin from multiple different parent bodies than the normal eucrites. Often the qualifier anomalous is used to identify HEDs with (delta)17O values that deviate significantly (>3(sigma)) from the mean HED (delta)17O. However, variations in eucrites and diogenites also include unique geochemical characteristics such as bulk composition, trace element abundances, or volatile concentrations, in addition to (delta)17O. Here, we investigate three such geochemically anomalous HEDs: Elephant Moraine (EET) 92023, Graves Nunataks (GRA) 98098, and Dhofar 700. In addition, to verify the homogeneity of (epsilon)54Cr observed for normal HEDs thus far, a set of seven eucrites and diogenites considered normal samples were also investigated.

Sanborn, M. E.↗
NASA NTRS2019

The Sariçiçek Howardite Fall in Turkey: Source Crater of HED Meteorites on Vesta and Impact Risk of Vestoids

The Sariçiçek howardite meteorite shower consisting of 343 documented stones occurred on September 2, 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sariçiçek experienced a complex cosmic‐ray exposure history, exposed during ~12–14 Ma in a regolith near the surface of a parent asteroid, and that an ~1 m sized meteoroid was launched by an impact 22 ± 2 Ma ago to Earth (as did one‐third of all HED meteorites). SIMS dating of zircon and baddeleyite yielded 4550.4 ± 2.5 Ma and 4553 ± 8.8 Ma crystallization ages for the basaltic magma clasts. The apatite U‐Pb age of 4525 ± 17 Ma, K‐Ar age of ~3.9 Ga, and the U,Th‐He ages of 1.8 ± 0.7 and 2.6 ± 0.3 Ga are interpreted to represent thermal metamorphic and impact‐related resetting ages, respectively. Petrographic; geochemical; and O‐, Cr‐, and Ti‐isotopic studies confirm that Sariçiçek belongs to the normal clan of HED meteorites. Petrographic observations and analysis of organic material indicate a small portion of carbonaceous chondrite material in the Sariçiçek regolith and organic contamination of the meteorite after a few days on soil. Video observations of the fall show an atmospheric entry at 17.3 ± 0.8 km/s from NW; fragmentations at 37, 33, 31, and 27 km altitude; and provide a pre‐atmospheric orbit that is the first dynamical link between the normal HED meteorite clan and the inner Main Belt. Spectral data indicate the similarity of Sariçiçek with the Vesta asteroid family (V‐class) spectra, a group of asteroids stretching to delivery resonances, which includes (4) Vesta. Dynamical modeling of meteoroid delivery to Earth shows that the complete disruption of a ~1 km sized Vesta family asteroid or a ~10 km sized impact crater on Vesta is required to provide sufficient meteoroids ≤4 m in size to account for the influx of meteorites from this HED clan. The 16.7 km diameter Antionia impact crater on Vesta was formed on terrain of the same age as given by the 4He retention age of Sariçiçek. Lunar scaling for crater production to crater counts of its ejecta blanketshow it was formed ~22 Ma ago.

Unsalan, Ozan↗
NASA NTRS1994

Grain size of the surface regolith of asteroid 4 Vesta estimated from its reflectance spectrum in comparison with HED meteorites

The grain-size distribution of the regolith of asteroid 4 Vesta has been estimated by comparing its reflectance spectra (0.3-2.6 microns) with those of HED meteorites. The finest grain-size separate (less than 25 micrometers) of a particular howardite has a reflectance spectrum most similar to Vesta's. In order to better simulate Vesta's surface mineralogy, reflectance spectra of those finest HED meteorite powders were linearly combined, and Vesta's spectrum was scaled for the best fit between them. Both the albedo and the shape of reflectance spectrum of Vesta were well reproduced by regional mixtures of the finest (less than 25 micrometers) powders of HED meteorites. The result suggests the heterogeneity of Vesta's surface and provides an estimate of the visible reflectance of Vesta that is close to its Infrared Astronomical Satellite (IRAS) albedo. Thus, this suggests that fine grains can be generated and retained by relatively small bodies (Vesta is approximately 500 km in diameter).

Hiroi, Takahiro↗
NASA NTRS1998

HEDS-UP Mars Exploration Forum

In the early 1990s, Duke and Budden convened a series of workshops addressing mission rationale, exploration objectives, and key constraints and issues facing human crews on Mars. The focal point was "why" the U.S. should fly humans to Mars. In the mid-1990s, strategies for a Mars mission matured and evolved, driven formally by NASA Johnson Space Center's Office of Exploration. In 1997, NASA published a report capturing the current thinking: the NASA Mars Reference Mission. In the 1997-1998 school year, HEDS-UP sponsored six universities to conduct design studies on Mars exploration, using the Reference Mission as a basis for their work. The 1998 Mars Exploration Forum presents the results of these university studies, suggesting "how" we might explore Mars, in terms of specific technical components that would enable human missions to Mars. A primary objective of the HEDS-UP Mars Exploration Forum was to provide a forum for active interaction among NASA, industry, and the university community on the subject of human missions to Mars. NASA scientists and engineers were asked to present the state of exploration for Mars mission options currently under study. This status "snapshot" of current Mars strategies set the stage for the six HEDS-UP universities to present their final design study results. Finally, a panel of industry experts discussed readiness for human missions to Mars as it pertains to the aerospace industries and technologies. A robust poster session provided the backdrop for government-industry-university discussions and allowed for feedback to NASA on the Mars Reference Mission. The common thread woven through the two days was discussion of technologies, proven and emerging, that will be required to launch, land, and sustain human crews on the Red Planet. As this decade (and indeed this millenium) draws to a close, Mars will continue to loom in our sights as the next target for human space exploration. It is our hope that the efforts of the Mars Exploration Forum will serve as one small contribution toward the ultimate goal of humans exploring Mars.

Budden, Nancy Ann↗
NASA NTRS2010

Petrology and Composition of HED Polymict Breccias

The howardite, eucrite and diogenite (HED) clan of meteorites forms the largest suite of achondrites with over 900 named members. The HEDs are igneous rocks and breccias of igneous rocks from a differentiated asteroid [1]. The consensus view is that these rocks hail from the asteroid 4 Vesta, which will be the first target of NASA's Dawn mission. When Dawn arrives at Vesta, she will begin remote imagery and spectroscopy of the surface. The surface she will observe will be dominated by rocks and soils mixed through impact gardening. To help with the interpretation of the remotely sensed data, we have begun a project on the petrologic and compositional study of a suite of HED polymict breccias. Here we report on the preliminary findings of this project.

Mittlefehldt, David W.↗
NASA NTRS2014

Vesta in the Light of Dawn, But Without HEDS?

The derivation of HEDs from Vesta is strongly supported by Dawn data [1], and these meterorites have made interpretations of Dawn spectra much more rigorous. Compared to the Moon, where samples became available after geologic mapping, the exploration of Vesta has been backwards. But what if HEDs had not been available or identified as vestan samples? What petrologic and geochemical predictions would have been possible using Dawn data, without the benefit of HEDs?

McSween, H. Y.↗
NASA NTRS2016

Catching Constrains on the Parent Body Genesis of Mesosiderites and a Possible Link to HED (Howardite-Eucrite-Diogenite) Meteorites - A New Hope?

Mesosiderites (MES) are a group of enigmatic stony-iron meteorites exhibiting fragmental matrix breccias and irregular textures; e.g. [1-3]. Mesosiderites contain roughly equal volumes metal (Fe-Ni) and silicates often intimately mixed together (Fig.1). The silicates mostly consist of basaltic, gabbroic, and pyroxenitic components, and appear similar to eucrites and howardites; [4-8]. But unlike HEDs - and other differentiated parent body meteorite groups e.g. ureilites - mesosiderites contain high metal abundances. Several studies have been published to reveal the processes leading to the formation of mesosiderites and attempt to classifiy them [1], [2], [10-15]. Because the silicate inclusions in mesosiderites are often strongly metamorphosed after formation, it is difficult to assess the origin of the silicates and implications for the differentiation process of their parent body [15-17]. Several workers have advanced a formation hypothesis for the mesosiderites where an impact between differentiated bodies occurred prior to 4.47 Ga ago (e.g. [13,18], which could explain the possible incomplete dispersal of the colliding bodies due to their low cosmic ray exposure ages and their special thermal history. However, [13] discuss and favor the model for formation of mesosiderites with the collision of two differentiated bodies, along with disruption events and gravitational re-assembly. The mesosiderites have numerous gabbroid melt clasts with anomalous rare-earth- element (REE) - especially positive Eu - values [19, 20]. HEDs do not show the same. However, the heating mechanisms of both mesosiderites and HED's are puzzling. Mesosiderites are remarkable, they consist of a mix of basalts, which are only found on or near planetary surfaces and undifferentiated metal [1,2]. The probable model is that an asteroid containing a metallic magma impacted onto a second asteroid covered with basalt [18,21]. The mix was then buried under an insulating regolith, and cooled slowly. During cooling and at low temperatures the redox reactions continued to occur and proceed (J.T. Wasson; in pers. comm. 2015).

Eucrite↗
NASA NTRS1994

Mineralogy and Ar-39 - Ar-40 of an old pristine basalt: Thermal history of the HED parent body

Previous investigations of mineral chemistry and Rb-Sr and Sm-Nd ages indicated that clast,84 from eucrite Yamato 75011 had preserved the pristine nature of its initial crystallization during an early stage of the HED parent body. Microscale mineralogy and Ar-39-Ar-40 ages of this clast, however, revealed local disturbance of microtextures and partially reset ages. This evidence suggests that, in addition to initial crystallization and rapid cooling, the Y75011,84 clast experienced shock deformation, reheating of short duration at higher temperature, and brecciation. These characteristics suggest two or more impact events. Fe-rich olivine filling fractures in pyroxene may have been introduced during the accompanying shock fracturing. The inferred Ar-39-Ar-40 degassing ages for Y75011 matrix and clast, 84 are 3.94 +/- 0.04 Ga and 3.98 +/- 0.03 Ga, respectively. The suggested degassing age for a clast from Y790020, believed to be paired with Y75011, is approximately 4.03 Ga, but could be younger. We consider it likely that all three samples experienced a common degassing event 3.95 +/- 0.05 Ga ago, but we cannot rule out two or more events spaced over a approximately 0.1 Ga interval. Higher temperature extractions of the two clast samples show significantly older apparent ages up to approximately 4.5 Ga and suggest that the time/temperature regime of this event was not sufficient to degas Ar totally. Most likely, the K-Ar ages were reset by thermal metamorphism associated with one or more impact events associated with shock fracturing, formation of Fe-rich olivine veins, and/or meteorite brecciation. The pyroxene annealing that commonly occurs in many eucrites is likely to be a much earlier process than the impact-produced textural changes and reset K-Ar ages observed in these meteorites. The existence of mineralogical and chronological evidence for metamorphism in an otherwise pristine eucrite suggests that the HED parent body experienced an extensive degree of early cratering.

Takeda, Hiroshi↗
NASA NTRS2002

Systems Integration, Analysis and Modeling Support to the HEDS Technology/Commercialization Initiative (HTCI)

In response to a recommendation from OMB, NASA's Fiscal Year 2001 budget included a new program within the HEDS (Human Exploration and Development of Space) Enterprise called HEDS Technology/ Commercialization Initiative (HTCI). HTCI had three overarching goals: to support REDS analysis and planning for safe, affordable and effective future programs and projects that advance human exploration, scientific discovery, and the commercial development of space; to pursue research, development, and validation of breakthrough technologies and highly innovative systems concepts; and to advance die creation of strong partnerships within NASA, with U.S. industry and universities, and internationally. As part of its contracted effort, SAIC was to write a report contribution, describing die results of its task activities, to a final HTCI report prepared by MSFC. Unfortunately, government cancellation of the HTCI program in the summer of 2001 curtailed all efforts on the program including die Final HTCI report. In the absence of that report, SAIC has issued this final report in an attempt to document some of the technical material it produced. The report contains SAIC presentations for both HTCI workshops; a set of roadmap charts for the Systems Analysis, Integration and Modeling; and charts showing the evolution of the current TITAN modeling architecture.

Feingold, Harvey↗
NASA NTRS2009

Chemical Mixing Model and K-Th-Ti Systematics and HED Meteorites for the Dawn Mission

The Dawn mission will explore 4 Vesta, a large differentiated asteroid believed to be the parent body of the howardite, eucrite and diogenite (HED) meteorite suite. The Dawn spacecraft carries a gamma-ray and neutron detector (GRaND), which will measure the abundances of selected elements on the surface of Vesta. This study provides ways to leverage the large geochemical database on HED meteorites as a tool for interpreting chemical analyses by GRaND of mapped units on the surface of Vesta.

Usui, T.↗
NASA NTRS2010

A Cabonaceous Chondrite Dominated Lithology from the HED Parent; PRA 04401

The paired howardite breccias Mt. Pratt (PRA) 04401 and PRA 04402 are notable for their high proportion of carbonaceous chondrite clasts [1]. They consist predominantly of coarse (0.1-7 mm) diogenite (orthopyroxene), eucrite (plagioclase + pyroxene), and carbonaceous chondrite clasts set in a finer grained matrix of these same materials. Coarse C-chondrite clasts up to 7 mm are composed mainly of fine-grained phyllosilicates with lesser sulfides and high-mg# anhydrous magnesian silicates. Most of these clasts appear to be texturally consistent with CM2 classification [1] and some contain relict chondrules. The clasts are angular and reaction or alteration textures are not apparent in the surrounding matrix. PRA 04401 contains about 70 modal% C-chondrite clasts while PRA 04402 contains about 7%. Although many howardites are known to contain abundant C-chondrite clasts [2,3,4], PRA 04401 is, to our knowledge, the most chondrite-rich howardite lithology identified to date. Low EPMA totals from CM2-type clasts in other howardites suggest that they frequently contain 10 wt% or more water [2], a figure consistent with their mineralogy. PRA 04401, therefore, demonstrates the potential for hydrous lithologies with greater than 5 wt% water to occur locally within the nominally anhydrous HED parent body. Since the origin of this water is xenogenic, it might therefore be concentrated in portions of the asteroid surface where it would be more readily observable by remote sensing techniques. We plan to further examine C-chondrite clasts in PRA 04401/2 with the intent of establishing firm chemical classification, estimating water content, and evaluating their relationship with the host breccia. To help place them in context of the HED parent, we will also compare these breccias with other howardites to evaluate which lithologies are likely to be more prevalent on the asteroid surface.

Herrin, Jason S.↗
NASA NTRS2016

Using VSWIR Microimaging Spectroscopy to Explore the Mineralogical Diversity of HED Meteorites

We use VSWIR microimaging spectroscopy to survey the spectral diversity of HED meteorites at 80-µm/pixel spatial scale. Our goal in this work is both to explore the emerging capabilities of microimaging VSWIR spectroscopy, and to contribute to understanding the petrologic diversity of the HED suite and the evolution of Vesta. Using a combination of manual and automated hyperspectral classification techniques, we identify four major classes of materials based on VSWIR absorptions that include pyroxene, olivine, Fe-bearing feldspars, and glass-bearing/featureless materials. Results show microimaging spectroscopy is an effective method for rapidly and non-destructively characterizing small compositional variations of meteorite samples and for locating rare phases for possible follow-up investigation. Future work will include incorporating SEM/EDS results to quantify sources of spectral variability and placing observations within a broader geologic framework of the differentiation and evolution of Vesta.

Fraeman, Abigail A↗
NASA NTRS1983

Mineralogical comparison of antarctic and non-antarctic HED (howardites-eucrites-diogenites) achondrites

Mineralogical examination of thin sections of non-Antarctic and Antarctic HED (howardite, eucrite, diogenite) achondrites indicates that they contain a variety of lithic components. Some of these components occur both as monomict meteorites and as clasts in polymict meteorites, whereas others occur only as clasts in some polymict breccias. The components may be classified by the degree of homogenization of the pyroxene present. In order of increasing homogeneity these are: (1) Y-75011-type basalt clasts; (2) Pasamonte; (3) Y-790266-type clasts; (4) Stannern and Nuevo Laredo; (5) Juvinas and Haraiya; and (6) Ibitira. Type 1 has been least modified by post-igneous thermal annealing, while types 5 and 6 were thoroughly metamorphosed. Three types of cumulate eucrites are recognized and are believed to represent (a) cumulates from thick lava flows or layered intrusions; (b) lunar highlands type crust; and (c) differentiation products of diogenitic magmas.

Takeda, H.↗
NASA NTRS1993

An improbable concentration of basaltic meteorite falls (HED and mesosiderite) in the mid-20th century

The present examination of the historical record of HED and mesosiderite basaltic meteorite falls attempts to determine whether that record is consistent with completely random fall times. Strong evidence for nonrandomness emerges, in view of a significant cluster of falls for the 1924-1939 period. The causes of the cluster appear to have acted only on basaltic meteorites, and in a way that was of only 15-year-duration.

Treiman, Allan H.↗
NASA NTRS1993

The EET87513 clast N: A CM2 fragment in an HED polymict breccia

Xenoliths of material resembling carbonaceous chondrites have been found in several HED polymict breccias. Most workers concluded that these clasts are related to CM2 meteorites on the basis of texture, bulk composition, and mineralogy. Data on clast N, a carbonaceous chondrite fragment from the howardite EET87513 large enough (approximately 4x5mm on the surface of the slab from which it was separated) to extract bulk samples for INAA and oxygen isotope analysis and to provide a thin section for electron microprobe, SEM, and TEM analysis is reported. Preliminary data for this clast were previously reported. INAA was performed at Oregon State University and bulk oxygen isotopic composition was determined at the University of Chicago. These data confirm that EET87513 clast N is a fragment of CM2 material.

Buchanan, P. C.↗
NASA NTRS1993

The thickness of eucritic crust in the HED parent body

Because cumulate eucrites are generally thought to be located at the lower part in eucritic crust on a diogenitic mantle in the HED parent body, the burial depth of cumulate eucrites gives information on the thickness of the eucritic crust. We estimated the burial depth and cooling rate of cumulate eucrites, Serra de Mage and Moore County on the basis of the width of augite lamellae and compositional gradients of Ca in pyroxenes by numerically solving the diffusion equation. We obtained the burial depth of the eucrites of 7-8 km and cooling rate of 0.00016-0.0002 degrees C/yr.

Miyamoto, M.↗
NASA NTRS1996

Workshop on Evolution of Igneous Asteroids: Focus on Vesta and the HED Meteorites

This volume contains papers that have been accepted for presentation at the Workshop. Topics considered include: On the sample return from Vesta by low-thrust spacecraft; Astronomical evidence linking Vesta to the HED meteorites; Geologic mapping of Vesta with the Hubble Space Telescope; A space mission to Vesta; Asteroid spectroscopy; The thermal history of asteroid 4 Vesta, based on radionuclide and collision heating; Mineralogical records of early planetary processes on Vesta.

Mittlefehldt, D. W.↗