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All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Developing Glassy Magnets from Simulated Composition of Martian Soil for Exploration Applications

The long-term exploration goals of NASA include developing human habitation on Mars and conducting scientific investigations on Mars and other planetary bodies. In situ resource processing is a key objective in this area. We focus on the possibility of making magnetic glasses in situ for potential applications development. The paper will focus on ongoing work at NASA Marshall Space Flight Center on making magnetic glass from Mars soil simulants and its characterization. Analysis of the glass morphology, strength, chemistry and resulting magnetic properties will provide a fundamental understanding of the synthesized material that can be used for potential applications development. in an effort to characterize the magnetic properties of the Mars glasses, a series of tests were performed at NASA MSFC. Preliminary tests indicated that the glasses were attracted to a magnet and also had a small amount of residual magnetism. They were opaque (almost black in color). As the first step, a sample of Mars 1 glass (approx.1 mm x 1 mm x 5 mm length) was machined, weighed and its hysteresis curve was measured using a Vibration Sample Magnetometer (VSM). Next, a small furnace was designed and built and the sample was baked in a graphite (reducing agent) crucible at 800 C in an Argon atmosphere for 3 hours in the presence of a uniform, transverse (transverse to the 5mm length of the sample) magnetic field of 0.37 Tesla. The treated sample showed reddening on the outside and showed substantially increased residual magnetism. This sample was again analyzed in the VSM. The data clearly showed that some chemical change occurred during the heat treatment (color change) and that both the glasses have useful magnetic properties. Although no orientation effects of the magnetic field were considered, the data showed the following: 1. Both glass samples are primarily soft magnets and display ferromagnetic behavior (hysteresis, saturation, etc.) 2. The treated glass has improved saturation magnetism (order of magnitude increase), retentivity (factor of 6 increase) and susceptibility (order of magnitude increase) compared to the untreated glass 3. The untreated sample has higher coercivity (approx.50% that of Nickel) than the treated sample 4. Both samples have similar energy density. Results from a systematic study to quantify the effects of processing conditions such as heat treatment, atmosphere, containerless processing (by electrostatic levitation), and applications of external magnetic fields of different strengths will be discussed. Efforts on optimizing the magnetic properties of the product and the feasibility of using it for a couple of specific magnetic applications such as heat generation using an ac field and for electro forming will also be covered. The latter is an in situ manufacturing technique being studied for in-space fabrication applications at MSFC.

Ramachandran, N.↗
NASA NTRS2024

Advanced Low Gravity Characterization and Liquid-phase Synthesis of Non-equilibrium and Glassy Oxides

Materials processing in space and the investigation, development and commercialization of non-equilibrium materials and glasses are key aspects of NASA’s BPS mission. The MATRICES project recommended by the Decadal Survey panels calls out key aspects that support development of new materials in space. These areas directly serve NASA space exploration mission and lay the basis to commercialize high value or enabling materials that can be produced in low gravity.

Chris Benmore↗
NASA NTRS1985

Hypervelocity impacts on Skylab 4/Apollo windows

The three largest Skylab 4 Command Module windows that were exposed for 84 days to space were optically scanned for impact features as small as 30 microns in diameter. This scanning effort which was carried out at an opptical magnification of 35x, detected features approximately three times smaller than were found in the original 5x scanning effort over the entire window surface. Some 289 features were recorded from the 35x scan for later detailed analyses. Sixty of the largest and most promising features were cored from the windows for SEM and energy-dispersive X-ray spectrometer (EDS) analysis. Twenty-six of the cores contained craters with glassy pits, and of these, fourteen were found to contain strikingly obvious liners coating the interior of the glassy pit. The six largest features cored from the windows do not have a central glassy pit which leaves their previously reported hypervelocity origin in some doubt. The remaining twenty-eight features that were cored from the windows show no clear evidence for a hypervelocity origin and evidence available at this time is insufficient to identify an origin in Earth orbit or as ground damage. The EDS analysis of six of the seven liners that were examined show detectable aluminum in the liner or lip of the glassy pit. The source of aluminum is most probably an Earth orbiting population of aluminum oxide spherules, exhaust from solid rocket motors.

Clanton, U. S.↗
NASA NTRS2012

Rb-Sr and Sm-Nd Isotopic Studies of Lunar Green and Orange Glasses

Lunar volcanic glassy beads have been considered as quenched basaltic magmas derived directly from deep lunar mantle during fire-fountaining eruptions [1]. Since these sub-mm size glassy melt droplets were cooled in a hot gaseous medium during free flight [2], they have not been subject to mineral fractionations. Thus, they represent primary magmas and are the best samples for the investigation of the lunar mantle. Previously, we presented preliminary Rb- Sr and Sm-Nd isotopic results for green and orange glassy samples from green glass clod 15426,63 and orange soil 74220,44, respectively [3]. Using these isotopic data, initial Sr-87/Sr-86 and Nd ratios for these pristine mare glass sources can be calculated from their respective crystallization ages previously determined by other age-dating techniques. These isotopic data were used to evaluate the mineralogy of the mantle sources. In this report, we analyzed additional glassy samples in order to further characterize isotopic signatures of their source regions. Also, we'll postulate a relationship between these two major mare basalt source mineralogies in the context of lunar magma ocean dynamics.

Shih, C.-Y.↗
NASA NTRS1972

Mineralogy and origin of Fra Mauro fines and breccias.

Textural features, glassy spherule and glassy aggregate contents, and size-frequency distributions of lithic components of the regolith fines indicate that the Fra Mauro regolith of the smooth terrain is a highly reworked accumulation of debris derived primarily by impact comminution of annealed breccias. Analyses of the glassy spherules suggest that mare-derived debris must amount to less than 5% of the regolith, but exotic materials having the composition of the Fra Mauro breccias (highland-like) cannot be recognized. Breccia samples from the Fra Mauro site include (1) regolith breccias derived by lithification of local regolith material, (2) texturally and compositionally unique white rock breccias that may have been derived from ancient ejecta buried beneath the Fra Mauro formation, and (3) annealed breccias that are excavated samples of the Fra Mauro formation. The latter were deposited as heated impact ejecta, probably by avalanches produced by the Imbrian event and were annealed in situ in a thermal regime perhaps equivalent to that responsible for the pyroxene-hornfels facies of metamorphism in terrestrial rocks.

Quaide, W.↗
NASA NTRS1980

Hypervelocity impacts on Skylab IV/Apollo windows

A description is presented of some new observations of crater morphology on the Skylab IV/Apollo windows. Aluminum is detected as the only foreign component in six of the seven lined glassy pit craters so far examined by EDS analysis. The most probable source is from aluminum oxide spherules, exhaust effluent of solid fuel rocket motors. The seventh crater contains titanium which may have been derived from an impact of a chip of thermal paint. The size distribution of the lined glassy pit craters appears to be compatible with an origin by hypervelocity impacts of aluminum spherules. If the aluminum oxide spherules are in earth orbit, impact velocities largely in the range of 7 to 10 km/s should be expected. Thus, the impact velocities are well below those expected for most impacts by micrometeorites and these lower velocities may be significant in the development of the lined glassy pit craters. The results indicate that there is a significant population of man-induced micro-debris in earth orbit.

Clanton, U. S.↗
NASA NTRS1983

High temperature deformation of hot-pressed polycrystalline orthoenstatite

Artificial hot pressed polycrystalline samples were prepared from purified powder of Bamble, Norway, orthoenstatite, (Mg0.86Fe0.14)SiO3. The uniaxial creep behavior of the polycrystalline orthoenstatite was studied over stress ranges of 10-180 MPa and temperatures of 1500-1700 K (0.82-0.93 T sub m) under two different oxygen fugacities, namely equilibrium (Mo-MoO2 buffer) and a reducing (graphite heating element) atmosphere, respectively. An intergranular glassy phase of different compositions with a cavitational creep deformation were observed. In the Mo-MoO2 buffer atmosphere with PO2 approx. 10 to the minus 11 power - 10 to the minus 13 power atmospheres, the results of an analytical electron microscopy analysis indicate that the glassy phases are richer in Ca and Al due to the residual impurities after hot pressing. In the reducing atmosphere with an oxygen fugacity of PO2 approx. 10 to the minus 3 power - 10 to the minus 25 power atmospheres, the results of analytical electron microscopy analysis indicate that the glassy phase is almost pure silica with the presence of free iron precipitate on grain facets and at triple junctions due to the reduction of bulk materials.

Dehghan-Banadaki, A.↗
NASA NTRS1992

Heat shield erosion in a dusty Martian atmosphere

The study calculates the effects of dust particle impacts on the erosion of the forebody heat shield for a 26-m diameter aerobraking vehicle entering the Martian atmosphere at 8.6 km/s. An explicit thin-layer Navier-Stokes code is used to compute the dustless flowfield about the vehicle for the actual Martian atmospheric composition. The deceleration and melting of the dust particles within the forebody shock layer was computed for dust spherules having initial diameters from 1 to 19 microns. All the particles began vaporizing shortly after entering the shock layer, but most survived to hit the heat shield surface. The two different heat shield materials considered were Shuttle ceramic tiles with glassy surfaces and a moderate-density ablator. For a vehicle with a ballistic coefficient of 200 kg/sq m, a glassy heat shield surface experienced an average of 7 mm of surface erosion, or 20 times the thickness of the glassy layer on ceramic tiles.

Papadopoulos, Periklis↗
NASA NTRS1992

Research core drilling in the Manson impact structure, Iowa

The Manson impact structure (MIS) has a diameter of 35 km and is the largest confirmed impact structure in the United States. The MIS has yielded a Ar-40/Ar-39 age of 65.7 Ma on microcline from its central peak, an age that is indistinguishable from the age of the Cretaceous-Tertiary boundary. In the summer of 1991 the Iowa Geological Survey Bureau and U.S. Geological Survey initiated a research core drilling project on the MIS. The first core was beneath 55 m of glacial drift. The core penetrated a 6-m layered sequence of shale and siltstone and 42 m of Cretaceous shale-dominated sedimentary clast breccia. Below this breccia, the core encountered two crystalline rock clast breccia units. The upper unit is 53 m thick, with a glassy matrix displaying various degrees of devitrification. The upper half of this unit is dominated by the glassy matrix, with shock-deformed mineral grains (especially quartz) the most common clast. The glassy-matrix unit grades downward into the basal unit in the core, a crystalline rock breccia with a sandy matrix, the matrix dominated by igneous and metamorphic rock fragments or disaggregated grains from those rocks. The unit is about 45 m thick, and grains display abundant shock deformation features. Preliminary interpretations suggest that the crystalline rock breccias are the transient crater floor, lifted up with the central peak. The sedimentary clast breccia probably represents a postimpact debris flow from the crater rim, and the uppermost layered unit probably represents a large block associated with the flow. The second core (M-2) was drilled near the center of the crater moat in an area where an early crater model suggested the presence of postimpact lake sediments. The core encountered 39 m of sedimentary clast breccia, similar to that in the M-1 core. Beneath the breccia, 120 m of poorly consolidated, mildly deformed, and sheared siltstone, shale, and sandstone was encountered. The basal unit in the core was another sequence of sedimentary clast breccia. The two sedimentary clast units, like the lithologically similar unit in the M-1 core, probably formed as debris flows from the crater rim. The middle, nonbrecciated interval is probably a large, intact block of Upper Cretaceous strata transported from the crater rim with the debris flow. Alternatively, the sequence may represent the elusive postimpact lake sequence.

Anderson, R. R.↗
NASA NTRS1993

Crosslinked polyimides prepared from N-(3-ethynylphenyl)maleimide

The compound N-(3-ethynylphenyl)maleimide (NEPMI) was used to prepare thermally stable, glassy polyimides which did not exhibit glass transition temperatures below 500 C. NEPMI was blended with the maleimide of methylene dianiline (BMI) and heated to form the polyimide. NEPMI was also mixed with Thermid 600 R, a commercially available bisethynyl oligomeric material, and heated to form a thermally stable, glassy polyimide. Lastly, NEPMI was blended with both BMI and Thermid 600 R to form thermally stable, glassy polyimides.

Gerber, Margaret K.↗
NASA NTRS1999

Lateral and Vertical Heterogeneity of Thorium in the Procellarum KREEP Terrane: As Reflected in the Ejecta Deposits of Post-Imbrium Craters

The Procellarum KREEP Terrane displays the highest concentrations of Th on the Moon. However, locations of elevated Th in this region appear to be random. As observed in the 5 deg per pixel equal-area Th data, and made more evident in the preliminary 2 deg data, Th is enhanced around the craters Aristillus, Aristarchus, Kepler, Mairan, the Apennine Bench formation, and the Fra Mauro region, while noticeably and unexpectedly lower in other locations (e.g., Archimedes, Copernicus, Eratosthenes, and Plato). We have examined the composition of the materials present in these regions with the goal of understanding the patchy nature to the distribution of Th and ultimately to decipher the geologic processes that have concentrated the Th. At present time, the published resolution of the Lunar Prospector Th gamma-ray data is low (5 deg per pixel), but this will soon be superceded by significantly higher-resolution data (2 deg per pixel). Even at this improved resolution, however, it is difficult to resolve the units that are the major source of Th. In an attempt to circumvent this problem, we employ the higher-resolution Clementine multispectral data for those regions mentioned above. We use the UV-VIS-derived compositional information and the spectral properties of craters, and their ejecta as drill holes through the mare-basalt surface to investigate the thickness and composition of underlying material. With this information we attempt to piece together the stratigraphy and geologic history of the Imbrium-Procellanim region. We processed the five-band multispectral data from the Clementine Mission (415, 750,900,950, and 1000nm) using ISIS software and calibration parameters developed by the USGS, Flagstaff, Arizona. Final image mosaics are in equal-area sinusoidal projection, and have a resolution of 250 m/pixel. Using the method of we produced maps of FeO and Ti02 composition. Here we examine the Th, FeO, and Ti02 composition and spectral properties of the craters discussed above and their ejecta, with the goal of describing the materials they excavate. One interpretation for the origin of the high-Th material is that subsurface KREEPy materials have been excavated by impact craters. The material excavated may be either volcanic KREEP (e,g., Apennine Bench Formation), KREEPy impact-melt breccia formed by the Imbrium impact (e.g., Fra Mauro Formation), or other KREEP-rich crustal material. Determining which type of material is responsible for the elevated Th and its extent is important to understanding the premare and possibly the prebasin stratigraphy of the Imbrium-Procellarum Region. Merging the 5 deg. Th data with the shaded relief map, we observe that the highest Th concentrations are not related to pre-Imbrium upper crustal materials. The Apennines, Alpes, and Caucasus Mountains represent the pre-Imbrian highlands material and do not express concentrations of Th, FeO, and TiO2 as high as the most Th-fich materials exposed within the Procellarum KREEP Terrane. We observe that, in general, these massifs contain 10-14 wt% FeO and 4-7 ppm Th. Determining whether the Th signal is from KREEP basalts or KREEPy impact-melt breccias cannot be done with the Clementine data because the two rock types are compositionally and mineralogically too similar (e.g., the Th-rich, mafic impact-melt breccias in the Apollo sample collection are dominated by a KREEP-basalt like component. Mapping-the distribution and sizes of craters and whether they display elevated Th concentrations or not, should reveal the depth and thickness of the KREEP-rich materials, and whether they are ubiquitous (i.e., impact-melt breccia) or more randomly distributed; this might be taken as an indicator of localized KREEP-basalt flows. Within the southeastern region of the Imbrium basin, there are two Th hot spots. The first is associated with the crater Aristillus, and the latter with the Apennine Bench Formation. Adjacent to these two hot spots are craters with a lower Th signature: Archimedes and Autolycus. We observe in the ejecta of Aristillus, a region of significantly lower FeO (10-14 wt%) relative to the surrounding mare basalt. The crater Autolycus, 50 km to the south, did not excavate similar low-FeO material. We suggest that the lower-FeO material in the ejecta of Aristillus corresponds to Th-rich material; the FeO content observed in Aristillus ejecta is comparable to that of KREEP basalt or mafic impact melt breccia (10-12 wt% FeO). We determine that this low FeO, Th-rich material is volcanic KREEP, as opposed to Imbrium impact melt, on the basis that the low-Fe material is exposed more prominently in ejecta in the northern portion of Aristillus. Our assumption is that if the layer underlying Aristillus was continuous, a more widespread and uniform low-Fe signature wouldbe observed in the ejecta deposit. Archimedes, 110 km southwest of Aristillus, impacted the northern portion of the Apennine Bench prior to the eruption of KREEP basalt. Archimedes rim material is not as enriched in Th as the Apennine Bench, and there are differences between the two in FeO concentration and in their continuum slope. Archimedes exhibits a much steeperor "redder" continuum slope than the Apennine Bench. This steepslope suggests the presence of glassy material. The glassy material is concentrated around an unnamed crater on the southern rim of Archimedes (4.5W, 28.2N) and along the northern rim of Archimedes. We suggest two possibilities, or a combination of the two, to explain the low-Th signal from Archimedes: (1) The Apennine Bench prior to KREEP basalt eruption was lower in Th (4-7 ppm, e.g., similar to the Apennine massifs) and KREEP basalts are absent in the rim of Archimedes; or (2) the glassy (possibly pyroclastic) material layering the rim of the Archimedes, dilutes any high-Th material present with low-Th material. (Additional information is contained in the original)

Gillis, J. J.↗
NASA NTRS2002

Iridium and Spherules in Late Eocene Impact Deposits

We have been independently examining the Ir (FTK) and spherule (SL) contents of recently discovered late Eocene impact deposits from the south Atlantic and western Indian oceans. These include ODP Sites 1090 [14,15], 709 [lo], and 699 [Liu in prep.]. Iridium abundances at these sites are within the typical range reported for late Eocene deposits, with peak concentrations between 100 and 1000 pg/g. In Table 1 we present estimated net Ir fluences (in ng Ir/cm ) for these and nine other sites. Although there are fewer sites than the K/T boundary, the average of 9 ng Ir/cm2 is probably a good estimate of the late Eocene global flux. This is enough Ir for a 6 km comet (assuming 250 ng/g Ir, p=1.5), is sufficient to produce the Popigai or Chesapeake Bay structures, and is 16% of the flux estimated for the K/T boundary (55 ng/cm2 [ 161). Figure 1 shows the relative abundances of Ir, glassy microtektites and cpx-bearing spherules in sediments from Sites 699 and 1090, which are separated by only 3100 km. Although these two sites have similar Ir anomalies, the abundances of spherules are quite different. Site 1090 has well-defined peaks for both types of spherules, with a peak of 562 cpx spheruledg, while Site 699 contains only a few glassy microtektites and no cpx spherules. While the different abundances of spherules may reflect a heterogeneous distribution of spherules on the Earth s surface, an equally likely cause of this difference may be differential preservation of spherules in the sediment. recovered are only a trace residue of the initial impact deposit. Earlier work found 0.22 ng/g Ir in glassy microtektites from Site 689 [17], an insufficient concentration to support 0.16 ng/g in the bulk sediment at this site. We measured 15 ng/g Ir in a group of 95 cpx spherules from Site 1090 with sizes from 63 to -200 pm, a set typical of the size distribution at this site. Although this is a significant concentration it also cannot support the Ir peak. We presently lack quantitative data on the mass concentration of cpx spherules in Site 1090 sediments, but it is certainly <1 mg/g in The impact record in the late Eocene is very different from that at the Cretaceous-Tertiary In contrast, the late Eocene probably experienced multiple impact events.

Kyte, F. T.↗
NASA NTRS2013

A Moderate D/H Ratio for a Surficial Water Reservoir on Mars

Martian surface morphology implies that Mars was once warm enough to maintain persistent liquid water on its surface and that water played a significant role in the formation of weathered/altered terrains [e.g., 1, 2, 3]. Volatiles exhaled by volcanic activity would have been the dominant greenhouse gases and would have significantly affected the Martian climate. The enrichment of some volatile elements in the atmosphere, which would have dissolved in surface water, could also have influenced water chemistry (e.g., acidity) and played a significant role in weathering and aqueous alteration processes. While much of this picture is qualitative, Martian meteorites contain records of major Martian volatile reservoirs. This study characterizes Martian surficial volatile reservoirs based on in situ ion microprobe analyses of volatile abundances and H-isotopes of glassy phases (groundmass glass [GG] and impact melt [IM]) in Martian basalts (shergottites). Although these meteorites are of igneous origin, some glassy phases underwent impact-induced modification that trapped surficial and atmospheric volatile components [4, 5]; e.g., inert gases contained in IMs from EETA79001 (EETA79) match the relative abundances of modern Martian atmosphere [6]. Analyses of these glassy phases demonstrate that surficial volatile reservoirs have distinct D/H ratios from their magmatic volatiles.

Usui, Tomohiro↗
NASA NTRS2017

A New Type of Foreign Clast in A Polymict Ureilite: A CAI or AL-Rich Chondrule

Introduction: Polymict ureilites are breccias interpreted to represent regolith formed on a ureilitic asteroid [1-3]. They consist of approximately 90-95% clasts of various ureilite types (olivine-pyroxene rocks with Fo 75-95), a few % indigenous feldspathic clasts, and a few % foreign clasts [4-20]. The foreign clasts are diverse, including fragments of H, L, LL and R chondrites, angrites, other achondrites, and dark clasts similar to CC [6,7,9-19]. We report a new type of foreign clast in polymict ureilite DaG 999. Methods: Clast 8 in Dar al Gani (DaG) 999/1 (Museum fur Naturkunde) was discovered during a survey of feldspathic clasts in polymict ureilites [19,20]. It was studied by BEI, EMPA, and X-ray mapping on the JEOL 8530F electron microprobe at ARES, JSC. Petrography and Mineral Compositions: Clast 8 is sub-rounded to irregular in shape, approximately 85 micrometers in diameter, and consists of approximately 68% pyroxene and 32% mesostasis (by area). Part of the pyroxene (top half of clast in Fig. 1a and 2) shows a coarse dendritic morphology; the rest appears massive. Mesostasis may be glassy and contains fine needles/grains of pyroxene. The pyroxene has very high CaO (23.5 wt.%) and Al2O3 (19.7 wt.%), with the formula: (Ca(0.91)Mg(0.63)Fe(0.01)Al(sup VI) (0.38)Cr(0.01)Ti(0.05)1.99 Si2O6. The bulk mesostasis also has very high Al2O3 (approximately 26 wt.%). A bulk composition for the clast was obtained by combining modal abundances with phase compositions (Table 1, Fig. 3). Discussion: The pyroxene in clast 8 has a Ca-Al-(Ti)- rich (fassaitic) composition that is clearly distinct from compositions of pyroxenes in main group ureilites [22] or indigenous feldspathic clasts in polymict ureilites [4-8]. It also has significantly higher Al than fassaite in angrites (up to approximately 12 wt.% [23]), which occur as xenoliths in polymict ureilites. Ca-Al-Ti rich pyroxenes are most commonly found in CAIs, Al-rich chondrules and other types of refractory inclusions in chondrites [21,24-31]. However, the clast 8 pyroxene matches only the most Al-Ca-rich of these, e.g., pyroxenes in type B CAIs in CV3 chondrites [25,30,31], a pyroxene-hibonite spherule and a pyroxene-anorthitespinel fragment from unique CC Acfer 094 [29], and one Al-rich chondrule from Chainpur (LL3.4) [21]. The mineralogy of clast 8 is not consistent with the mineral assemblages of any of these objects (since it lacks hibonite, spinel and/or anorthite), which suggests that it is unrepresentatively sectioned or is a fragment of a more mineralogically diverse object. Its bulk composition (Table 1; Fig. 3) is similar to bulk compositions of some Al-rich chondrules, as well as those of Type C CAIs (which plot in the sp+An+L field in Fig. 3), although it is enriched in silica relative to type C CAIs [e.g., 31]. This suggests a more likely affinity to Al-rich chondrules, although most Al-rich chondrules have less Al-Ca-rich pyroxene [21,26,27]. These bulk compositional comparisons may not be definitive, however, if the clast is unrepresentatively sampled. One of eleven Al-rich chondrules from UOCs described by [21] has textural and compositional characteristics that make it a possible progenitor type for clast 8. This chondrule (Chainpur 1251-14-2) is anorthiteporphyritic, with an interstitial dendritic intergrowth of pyroxene (similar in composition to that in clast 8) and plagioclase [21]. Clast 8 is conceivably a fragment from the interstitial area of such an object. The occurrence of glassy mesostasis (in clast 8) rather than plagioclase may not be a significant difference; it could result from a difference only in cooling rate. Al-rich chondrules with glassy mesostasis are rare, and known occurrences are Ca-poor [26], unlike clast 8. Polymict ureilites are known to contain xenoliths of various chondrites (including OC, R and CC) as well as individual ferromagnesian and silica-pyroxene chondrules probably derived from OC or RC [6,9,15,16,18]. This is the first report of an individual chondritic refractory inclusion as a xenolith in a polymict ureilite. An RC-like sample from anomalous polymict ureilite Almahata Sitta contains CAIs, but they are spinel-rich and not similar to clast 8 [13,14]. Further studies of this clast (which, unfortunately, may not be possible), or the discovery of additional (more representative?) materials of this type would be needed to determine the exact nature of this xenolith and the type of chondrite from which it is derived.

Goodrich, C. A.↗