Martian One of the Martian SNC meteorites, nakhlites are basaltic cumulate clinopyroxenite rocks, and most all are comprised mainly of sub-calcic augite with approximately 10% Fe-rich olivine (giving the augite a green color) that are set in a very fine-grained matrix (mesostasis) comprised of plagioclase, K-feldspar, clinopyroxene, Fe-Ti oxide (Ti-magnetite), sulfide, Click on Term to Read More
Found Spring 2009
no coordinates recorded Two moderately weathered friable stones having a combined weight of 145 g were found by nomads in Mauritania and subsequently sold to A. Habibi in Erfoud, Morocco. A portion of the Work in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and Click on Term to Read More was submitted for analysis and classification to the Université Pierre & Marie Curie in France (A. Jambon, O. Boudouma, D. Badia) and the Université de Bretagne Occidentale in France (J-A. Barrat). Oxygen-isotopic values were determined at the Open University in the UK (R. Greenwood and I. Franchi) to be consistent with a martian origin, and NWA 5790 was classified as a unique unpaired member of the nakhlite meteorite suite. During the same time period, two more conjoint stones weighing together 270 g were found and sold in Erfoud, Morocco to A. Aaronson. Analysis of these stones was conducted at Northern Arizona University (T. Bunch and J. Wittke), and NWA 6148 was determined to be paired with NWA 5790.
Diagram credit: © J. Dottin III, Master of Science Thesis (2016)
Geology and Earth Definable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with Sciences Interdisciplinary Center, University of Maryland, College Park
‘Assessing the Oxidative History of Miller Range Martian Meteorites’
(https://drum.lib.umd.edu/bitstream/handle/1903/18769/DottinIII_umd_0117N_17502.pdf) It is notable that NWA 5790/6148 is the most evolved nakhlite known, containing the highest Th, U and Often abbreviated as “REE”, these 16 elements include (preceded by their atomic numbers): 21 scandium (Sc), 39 Yttrium (Y) and the 14 elements that comprise the lanthanides excluding 61 Promethium, an extremely rare and radioactive element. These elements show closely related geochemical behaviors associated with their filled 4f atomic orbital. Click on Term to Read More concentrations reported thus far in a nakhlite as well as a having a strong LREE enrichment. The enrichment of Fe and LREE in the alteration phase of NWA 817 has been attributed to the infiltration of fluids, which had incorporated a dissolved Also referred to as the plagioclase feldspar series. Plagioclase is a common rock-forming series of feldspar minerals containing a continuous solid solution of calcium and sodium: (Na1-x,Cax)(Alx+1,Si1-x)Si2O8 where x = 0 to 1. The Ca-rich end-member is called anorthite (pure anorthite has formula: CaAl2Si2O8) and the Na-rich end-member is albite Click on Term to Read More component, into the local pre-existing rock. By the same token, since NWA 998 has the lowest REE abundance of any nakhlite, it might be attributed to its low retention of intercumulus melt reflected in its relatively small volume of mesostasis (~2%). Although this same process which affected the NWA 817 REE concentration has been considered as a possible explaination for the high REE concentration in NWA 5790/6148, the lack of ‘iddingsite’ in most studies of this meteorite suggests that fluid infiltration was not prevalent at its location, or alternatively, the scarcity of olivine in this meteorite was not conducive to the development of significant permeability (Tomkinson et al. 2015). Studies have revealed that NWA 5790/6148 contains a very low abundance of water (1–19 ppm in select pyroxene grains; A. Peslier, 2013). Through comparisons with nakhlites derived from other locations within the pile, it was determined that water abundances are not correlated with either the location or the cooling rate. McKay et al. (2006) observed that complex correlations exist between the Al content and the cooling rate among the nakhlites. For instance, those containing the most rapidly cooled pyroxenes contain both the highest content of Al in augite cores and the greatest homogeneity, while those that experienced slower cooling rates exhibit complex Al zoning and a In the context of planetary formation, the core is the central region of a large differentiated asteroid, planet or moon and made up of denser materials than the surrounding mantle and crust. For example, the cores of the Earth, the terrestrial planets and differentiated asteroids are rich in metallic iron-nickel. Click on Term to Read More Al content with a pronounced bimodal distribution. NWA 5790/6148 clearly has the highest Al value among the nakhlites and is inferred to have crystallized closest to the top or margins of the pile or lava flow(s); curiously, NWA 998 does not follow this trend. Mikouchi et al. (2014) conducted an examination of all known nakhlites (with the exception of the most recently recognized nakhlites) and have identified major Substance composed of atoms, each of which has the same atomic number (Z) and chemical properties. The chemical properties of an element are determined by the arrangement of the electrons in the various shells (specified by their quantum number) that surround the nucleus. In a neutral atom, the number of Click on Term to Read More chemical zoning in the olivine grains of each member indicative of rapid cooling. Across the respective zoning profiles, they found that the range of variation decreased in the following order: MIL pairing group and NWA 817 (Fa54–93) ⇒ Y-000593 pairing group (Fa58–85) ⇒ Nakhla and Governador Valadares (Fa58–72) ⇒ Lafayette and NWA 998, the latter two approaching homogeneity (Fa66–67 and Fa61–62, respectively). The fact that this chemical zoning in olivine reflects differences in cooling rates, as opposed to the possibility that the gradients were inherited from the magma, was demonstrated by Sio et al. (2014). They measured core to rim Mg-isotopic Movement of particles from higher chemical potential to lower chemical potential (chemical potential can in most cases of diffusion be represented by a change in concentration). Diffusion, the spontaneous spreading of matter (particles), heat, or momentum, is one type of transport phenomena. Because diffusion is thermally activated, coefficients for diffusion Click on Term to Read More profiles in the olivine grains of certain members of the nakhlite suite, and concluded that the existence of such isotopic fractionation was consistent with chemical diffusion during an extended cooling period. The fact that NWA 5790/6148 is the sole member of the nakhlite group which has retained complex primary zoning features on augite grains indicates that it cooled the fastest among the nakhlites, and this is consistent with a position at the top of the nakhlite pile or specific lava flow. Based on calculations of the growth rate of oscillatory zoning profiles in olivine and augite, A. Jambon (2014) concluded that simultaneous crystallization of both minerals occurred over a period of ~1 hour. Further evidence for rapid cooling at this upper-most (or margin) location can be seen in the Cl contamination previously identified in the MIL pairing group, in the high proportion of evolved mesostasis, and in the lack of Term used to describe physical or chemical stasis. Physical equilibrium may be divided into two types: static and dynamic. Static equilibrium occurs when the components of forces and torques acting in one direction are balanced by components of forces and torques acting in the opposite direction. A system in static Click on Term to Read More among the Inorganic substance that is (1) naturally occurring (but does not have a biologic or man-made origin) and formed by physical (not biological) forces with a (2) defined chemical composition of limited variation, has a (3) distinctive set of of physical properties including being a solid, and has a (4) homogeneous Click on Term to Read More phases. Based on textural and mineralogical characteristics, including mesostasis (REE) abundance, plagioclase size, olivine Fa composition, intercumulus The volume percentage of a rock that consists of void space. Vesicular porosity is a type of porosity resulting from the presence of vesicles, or gas bubbles, in igneous rock such as the pumice presented here. Vesicular porosity is very rare in meteorites and is often associated with slag, one Click on Term to Read More, closure temperature, Used to express the idealized partial pressure of a gas, in this case oxygen, in a nonideal mixture. Oxygen fugacity (ƒO2) is a measure of the partial pressure of gaseous oxygen that is available to react in a particular environment (e.g. protoplanetary disk, Earth's magma, an asteroid's regolith, etc.) and Click on Term to Read More, pyroxene composition (Mg#), Fe–Mg and Ca-zoning profiles in olivine and pyroxene, Li zoning profiles in augite, Al-content in pyroxene cores (see diagram below), crystal size distribution analysis, and Substances which have a tendency to enter the gas phase relatively easily (by evaporation, addition of heat, etc.). history, a comparative burial depth within the ~100 m nakhlite pile (magma chamber and/or lava flow) for each of the nakhlites and the chassignites is inferred as follows (Mikouchi et al., 2003, 2005, 2006, 2012, 2014; Lentz and McSween, 2003; Macrì et al., 2004; Imae et al., 2005; Day et al., 2006; McKay et al., 2006; Treiman and Irving, 2008; Jambon et al., 2010; Szymanski et al., 2010; McCubbin et al., 2013; Corrigan et al., 2014; Richter et al., 2015; Hewins et al., 2015; Giesting et al., (2015); Richter et al., 2016; Mikouchi et al., 2017):
- NWA 5790/6148: cooling 0.35 to 4.5 °C/hr; 34% mesostasis; olivine Fa94; top of the nakhlite pile, <2 m deep
- MIL 03346 pairing group: cooling 0.04 to 11.0 °C/hr; 22% mesostasis; olivine Fa92; near top, <2 m deep
- NWA 817: cooling 0.5 to 2.2 °C/hr; 24% mesostasis; olivine Fa90; near top, <2 m deep
- Y-000593/749/802: cooling 0.015 to 0.03 °C/hr; 10% mesostasis; olivine Fa85; 7 m deep
- Nakhla: cooling 0.01 to 0.04 °C/hr; 8% mesostasis; olivine Fa72; ~10 m deep
- Governador Valadares: cooling 0.01 to 0.085 °C/hr; 7% mesostasis; olivine Fa70; ~10 m deep
- NWA 10153: cooling ~0.01 °C/hr; ~25% mesostasis; ~10 m deep
- Lafayette: cooling <0.001 to <0.015 °C/hr; 7% mesostasis; olivine Fa67; up to >30 m deep
- NWA 998: cooling <0.0009 to <0.015 °C/hr; 7–10% mesostasis; olivine Fa62; up to >30 m deep
- unsampled olivine–Low-Ca clinopyroxene, (Ca,Mg,Fe)SiO3, found as a major mineral in eucrites and shergottites. In order to be considered pigeonite, the clinopyroxene must contain 5 to 20 mol % of calcium (Wo5 - 20). Chondrites of petrologic types 4 and below contain significant low-Ca clinopyroxene. During metamorphism to higher temperatures, all existing horizon
- NWA 8694: cooling 0.003 to 0.1 °C/hr; olivine Fa46
- Chassigny: cooling 0.003 to 0.1 °C/hr; 7% mesostasis; olivine Fa31
- NWA 2737: cooling 0.003 to 0.1 °C/hr; 6% mesostasis; olivine Fa21; greatest depth (<200 m)
Diagram credit: McKay et al., LPSC 37, #2435 (2006) To account for the difference in trace element ratios that is observed between the chassignites and the nakhlites, McCubbin et al. (2013) suggested that an exogenous Cl-rich, LREE-enriched fluid was introduced during initial crystallization and accumulation of olivine and Brownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups. Click on Term to Read More, as sampled by the chassignites, and prior to crystallization of clinopyroxene and olivine (±Orthorhombic, low-Ca pyroxene common in chondrites. Its compositional range runs from all Mg-rich enstatite, MgSiO3 to Fe-rich ferrosilite, FeSiO3. These end-members form an almost complete solid solution where Mg2+ substitutes for Fe2+ up to about 90 mol. % and Ca substitutes no more than ~5 mol. % (higher Ca2+ contents occur Click on Term to Read More), as sampled by the nakhlites. Subsequent draining/degassing of this Cl-rich fluid from the accumulating nakhlite pile was accompanied by preferential removal of Fe+2 over Fe+3 from the residual magma, which concurrently increased the Oxidation and reduction together are called redox (reduction and oxidation) and generally characterized by the transfer of electrons between chemical species, like molecules, atoms or ions, where one species undergoes oxidation, a loss of electrons, while another species undergoes reduction, a gain of electrons. This transfer of electrons between reactants Click on Term to Read More of the system. McCubbin et al. (2013) also reasoned that such an infiltration of metasomatic fluid into the chassignite–nakhlite cumulate pile would produce an olivine–pigeonite layer between the The group is part of the SNC martian trio and named after the meteorite seen to fall in Chassigny, France, in 1815. Its subsequent recovery led to it being one of the first meteorites to be recognized as a genuine rock from space. Chassigny resembles a terrestrial dunite - a Click on Term to Read More and nakhlite horizons, although such a lithology is not yet represented in our meteorite collections. Interestingly however, Krzesińska et al. (2017) have identified cumulate pigeonite grains in two small pyroxene-bearing fragments in Chassigny which they infer were derived from this hypothesized olivine–pigeonite layer prior to its final crystallization. Moreover, they found unique µm-scale aggregates associated with these pyroxene-bearing fragments that consist primarily of sulfide phases incorporating µm-sized metallic grains of Pb, Hg, Ag, The astronomical unit for length is described as the "mean" distance (average of aphelion and perihelion distances) between the Earth and the Sun. Though most references state the value for 1 AU to be approximately 150 million kilometers, the currently accepted precise value for the AU is 149,597,870.66 km. The Click on Term to Read More, and Sn. It is considered likely that these Element that readily forms cations and has metallic bonds; sometimes said to be similar to a cation in a cloud of electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. A diagonal line drawn Click on Term to Read More grains were introduced to the cumulate pile through the Cl-rich metasomatic fluid.
- Augite crystallized from an evolved Main silicate-rich zone within a planet between the crust and metallic core. The mantle accounts for 82% of Earth's volume and is composed of silicate minerals rich in Mg. The temperature of the mantle can be as high as 3,700 °C. Heat generated in the core causes convection currents in Click on Term to Read More melt and accumulated at the bottom of a sub-surface magma chamber. Multiple melt batches involving variable degrees of fractionation produced the compositional variation observed among the nakhlites.
- Subsequently these augite cumulus crystals (glomerocrysts) were disrupted and entrained by a more evolved magma flow. As a consequence the augites sustained crystal damage and partial resorption.
- This ascending magma erupted to the surface where lower pressures promoted crystallization of olivine, incorporating the augite cores as xenocrysts.
- Growth of olivine continued for a time followed by a final overgrowth of augite, all of which halted when the melt drained away and a rapid cooling stage ensued.
- Multiple successive lava flows ultimately formed a layered cumulate pile with nakhlites within different Originally horizontal layers of rock. exhibiting compositional variability, as illustrated by Jambon et al. (2016) in the diagram below:
Diagram credit: Jambon et al., GCA, vol. 190, p. 209 (2016)
‘Northwest Africa 5790: Revisiting nakhlite petrogenesis’ (http://dx.doi.org/10.1016/j.gca.2016.06.032) In their scenario, Jambon et al. (2016) envision NWA 5790/6148 at the top of the earliest lava flow where the rock experienced very rapid cooling, thereby limiting compaction (reflected in the lowest degree of preferred orientation of augite crystals among nakhlites) and equilibration through diffusion, and enabling the retention of a relatively large volume of mesostasis. They argue that the final position of NWA 5790/6148 was at the bottom of a stratified cumulate pile, a location which prevented the occurrence of secondary low-temperature hydrous alteration consistent with the observed absence of ‘iddingsite’ in their study of this nakhlite. In their diagram of the nakhlite cumulate pile, NWA 998 and NWA 817 are located within the intermediate flow zone based on several features they have in common; e.g., they have similar augite core compositions which are distinct from all other nakhlites, they have high incompatible element abundances (similar also to NWA 5790/6148), and they have similar Fe oxide, Fe2+Fe3+2O4, containing oxidized iron (Fe3+) found in the matrix of carbonaceous chondrites and as diagnostic component in CK chondrites. In CK chondrites, magnetite is typically chromian, containing several wt. % Cr2O3. Click on Term to Read More abundances. The top flow contains those nakhlites with similar augite core compositions as well as those with a high abundance of secondary aqueous alteration minerals; Nakhla is considered to have resided near the bottom of this stratum.
Diagram credit: Balta et al., MAPS, vol. 52, #1, p. 56 (2017) and references therein
‘Northwest Africa 5790: A previously unsampled portion of the upper part of the nakhlite pile’
Color background adapted from Jambon et al., GCA, vol. 190, p. 209 (2016)
‘Northwest Africa 5790: Revisiting nakhlite petrogenesis’
(http://dx.doi.org/10.1016/j.gca.2016.06.032) After a precise accounting and correction for the trapped (from martian atmosphere), radiogenic (from in situ 40K), and cosmogenic (from cosmic-ray exposure; weighted mean age = 10.7 [±0.8] m.y.) Ar components in six nakhlites (Lafayette, Y-000593, Y-000749, NWA 5790, Nakhla, and MIL 03346), Cohen et al. (2017) calculated a high-resolution 40Ar/39Ar age for each different nakhlite; they consider that these ages reflect the timing of the respective source lava eruption. The data show that these nakhlites erupted over a timespan of 93 (±12) m.y.—between 1.416 (±0.007) and 1.322 (±0.010) b.y. ago. They suggest that these six nakhlites represent at least four distinct sequential lava flows from a single plume-fed volcano, and that the flows were stratigraphically ordered commensurate with the nakhlite Ar chronometry data (see diagram below). Importantly, because of the incongruent eruption ages of the two Yamato nakhlites—a separation of 70 (±10) m.y.—it can be inferred that their source lithologies on Mars were located far apart, and therefore it is improbable that they are fall-paired.
click on image for a magnified view Diagram credit: Cohen et al., Nature Communications, vol. 8, #640, pp. 1–9 (2017, open access link)
‘Taking the pulse of Mars via dating of a plume-fed volcano’
(https://doi.org/10.1038/s41467-017-00513-8) Analyses of the most recent nakhlite Meteorite not seen to fall, but recovered at some later date. For example, many finds from Antarctica fell 10,000 to 700,000 years ago. Click on Term to Read More, NWA 10153 and pairings, has been published by investigators including Mikouchi et al. (2016, 2017). They report that this nakhlite contains ~25–30% interstitial mesostasis similar to the abundances in NWA 817 and MIL 03346 which are considered to have cooled rapidly near the top of the cumulate pile. However, the coarse nature of the An alumino-silicate mineral containing a solid solution of calcium, sodium and potassium. Over half the Earth’s crust is composed of feldspars and due to their abundance, feldspars are used in the classification of igneous rocks. A more complete explanation can be found on the feldspar group page. Click on Term to Read More in NWA 10153 (0.2–0.3 mm laths) is similar to that in NWA 998 (0.5 mm laths) which is considered to have cooled slowly near the bottom of the pile. Augite core compositions in NWA 10153 are similar to those of all other nakhlites, consistent with their crystallization from a common parental melt. This nakhlite exhibits complex chemical zoning in olivine and augite—the augite zoning is unlike that in any other nakhlite. Based on the Ca-Fe-Mg zoning profile, the cooling rate was determined to be 0.01–0.05 °C/hr; this is similar to that for Nakhla, GV, and Y-000593, which are considered to have crystallized at an intermediate depth within the pile. While Nakhla and other nakhlites from intermediate depths contain carbonates and halides, these are absent in NWA 10153. Low-temperature secondary aqueous alteration products (silicate gel phase) have been observed in both mesostasis and olivine fractures, a mineralogy common to the nakhlites near the top of the pile (Hicks et al., 2016). Another unique feature of this nakhlite is its significantly higher initial Nd-isotopic values and lower initial Hf-isotopic values compared to other nakhlites (Righter et al., 2016). Because of the ambiguous nature of NWA 10153, its position within a specific stratum in the nakhlite cumulate pile or lava flow(s) has not yet been determined; however, the combined data suggest a separate flow or lobe. A crystal size distribution analysis of nakhlites conducted by Udry and Day (2018) also shows that the NWA 10153 pairing group differs from other nakhlites; pyroxene is texturally much coarser and plagioclase is more abundant, and therefore a separate source lava flow or sill is indicated. In addition, a trace-element analysis conducted by Udry and Day (2018) demonstrates a division of nakhlites into two distinct groups—high trace-element abundance and low trace-element abundance (see diagram below). Grouping By Trace-Element Abundance
Diagram credit: Udry and Day, 49th LPSC, #1052 (2018)
High TE Nakhlites: MIL 03346 pairing group, NWA 817, NWA 5790/6148, NWA 10153 pairing group, NWA 10645
Low TE Nakhlites: Governador Valadares, Lafayette, Nakhla, NWA 998, Y-000593 pairing group An in-depth study of nearly all known nakhlites and chassignites was conducted by Udry and Day (2018). The results of petrological and geochemical analyses led them to propose a more complex emplacement scenario for these meteorites involving fractional crystallization and variable cooling rates within subsurface sills/dikes and multiple lava flows/lobes (see schematic illustration below). Some of the reasons for distinguishing at least seven distinct magma units are as follows:
- NWA pairing group 1 (NWA 10153, NWA 10659, NWA 10720, and NWA 11013 pairing group):
- No carbonates or salts have been observed in NWA 10659, distinguishing it from Lafayette, Governador Valadares, and Nakhla (Hicks et al., 2016)
- NWA 10153 has a distinct initial ε143Nd and ε176Hf isotopic composition compared to the other nakhlites (Righter et al., 2016)
- Contain crystalline plagioclase, low abundances of phenocrysts, and similar pyroxene compositions (Udry and Day, 2018)
- NWA 11013 has an Applied to mineral morphology: bristly, spiny, and needle-like. Click on Term to Read More rather than prismatic texture (Udry and Day, 2018)
- Contain reddish saponitic clay which suggests emplacement and subsequent alteration close to the surface (Hicks et al., 2016)
- Do not fit the general proposed cumulate pile stratigraphy (Udry and Day, 2018)
- NWA 10645:
- Pyroxene shows patchy zoning for Mg that has not been previously observed in nakhlites and chassignites (Udry and Day, 2018)
- Olivine grains are more Fe-rich (Fo13–22) than those in NWA 11013 (Fo13–39) (Udry and Day, 2018)
- Olivine abundances vary from 1.7 vol% in NWA 10645 (Udry and Day, 2018) to 18 vol% in NWA 10153 (Mikouchi et al., 2016)
- Pyroxene grains have acicular rather than prismatic textures and reach lengths of 4 mm, the largest pyroxene grains of all nakhlites (Udry and Day, 2018)
- Contains crystalline and blocky plagioclase, a low content of phenocrysts, and late-stage olivine (Udry and Day, 2018)
- Pyroxene has a shallower crystal size distribution slope (growth history of crystal populations) (Udry and Day, 2018)
- Contains reddish saponitic clay which suggests emplacement and subsequent alteration close to the surface (Hicks et al., 2016)
- NWA pairing group 2 (NWA 5790 and NWA 6148):
- Evidence of lower compaction compared to the other nakhlites (Balta et al., 2016)
- Quenched texture indicates likely formation close to the surface (Udry and Day, 2018)
- More evolved and enriched in incompatible elements compared to the other nakhlites (Udry and Day, 2018)
- NWA 817:
- Experienced less compaction than the other nakhlites (Udry and Day, 2018)
- Pyroxene compositions and R-value (grain clustering statistics from SDP analysis) suggest emplacement in a separate flow or sill (Udry and Day, 2018)
- Significant difference in ejection age compared to the other nakhlites and chassignites (7.3 m.y.; Wieler et al., 2016); therefore, NWA 817 possibly originates from a different impact site on Mars (Udry and Day, 2018)
- Miller Range and Yamato pairing groups:
- Apatite populations are similar (McCubbin et al., 2013)
- Textures are consistent (Udry and Day, 2018)
- Nakhla, Governador Valadares, Lafayette, and NWA 998 (the latter might be a separate flow based on apatites; McCubbin et al., 2013):
- Apatite populations are similar (McCubbin et al., 2013)
- Textures are consistent (Udry and Day, 2018)
- Mesostasis abundance is consistent near 10 vol% (Corrigan et al., 2015)
- Chassigny and NWA 2737 (and NWA 8694):
- Olivines abundances are nearly identical (Udry and Day, 2018)
- Textures and mineral compositions are consistent (Udry and Day, 2018)
Image credit: Udry and Day, GCA, vol. 238, p. 312 (2018)
‘1.34 billion-year-old magmatism on Mars evaluated from the co-genetic nakhlite and chassignite meteorites’
(https://doi.org/10.1016/j.gca.2018.07.006) Importantly, Mikouchi et al. (2016) found that significant ambiguities also exist among the three known chassignites. Although each chassignite exhibits a similar cooling rate (0.003–0.1 °C/hr), olivine compositions between them show large variations: NWA 8694 is Fa46, Chassigny is Fa31, and NWA 2737 is Fa21. Moreover, each chassignite exhibits a distinct shock history. Therefore, they suggest that each of the chassignites is more likely associated with a separate flow or lobe (possibly within a common extensive igneous unit) rather than a single sequential accumulation (see above schematic diagram as proposed by Balta et al.  illustrating separate lobes). In a study of the paired NWA 6148 employing Raman Technique of splitting electromagnetic radiation (light) into its constituent wavelengths (a spectrum), in much the same way as a prism splits light into a rainbow of colors. Spectra are not smooth but punctuated by 'lines' of absorption or emission caused by interaction with matter. The energy levels of electrons in coupled to a Scanning Electron Microscope system, Torre-Fdez et al. (2017) identified two rare phases: the first occurrence in a meteorite of cobalt (II, III) oxide, and the presence of calcite (CaCO3). A reasonable case was made for both a martian and a terrestrial origin for these minerals. Since cobalt mines are found in relatively close proximity to the recovered meteorite, the mineral could have been assimilated with the meteorite augite upon impact; however, the form of cobalt present in the meteorite, Co3O4, is not found naturally on Earth. Calcite on the other hand is a common mineral often associated with extensive terrestrial weathering; however, Torre-Fdez et al. (2018) found that the calcite Raman spectra indicate a high-pressure (>1.7 GPa) transformation to calcite II and/or calcite III (2–10 GPa). This shock-induced signature band (204 cm–1) is consistent with The body from which a meteorite or meteoroid was derived prior to its ejection. Some parent bodies were destroyed early in the formation of our Solar System, while others like the asteroid 4-Vesta and Mars are still observable today. Click on Term to Read More ejection or impact on Earth, and attests to the presence of calcite as a primary martian mineral. From data obtained by the Infrared Mineralogical Mapping Spectrometer aboard the Mars Express orbiter, olivine-enriched craters in the region of Thaumasia Planum were found to be the best match to the nakhlites (Ody et al., 2013). The high-resolution 40Ar/39Ar mid-Amazonian age determined for six nakhlites by Cohen et al. (2017) led them to the identification of a potential source Bowl-like depression ("crater" means "cup" in Latin) on the surface of a planet, moon, or asteroid. Craters range in size from a few centimeters to over 1,000 km across, and are mostly caused by impact or by volcanic activity, though some are due to cryovolcanism. Click on Term to Read More (see image below). This 6.5 km-diameter crater is located at 130.799°E, 29.674°N in the Elysium region and was formed in a recent impact event. High-resolution Body in orbit (such as a moon) around another larger body (such as a planet or star). Click on Term to Read More imagery shows a stratigraphic layering within the walls of the crater, and the calculated depth of Fractured and/or molten rocky debris thrown out of a crater during a meteorite impact event, or, alternatively, material, including ash, lapilli, and bombs, erupted from a volcano. Click on Term to Read More which would have reached Velocity that an object needs to escape the primary gravitational influence of a more massive object: where, m = the object's mass, r = distance from object's center, and G = gravitational constant of the larger object. Click on Term to Read More, 40–66 m, is consistent with the depth profile ascertained for the various nakhlites and chassignites.
Image credit: Cohen et al., Nature Communications, vol. 8, #640, pp. 1–9 (2017, open access link)
‘Taking the pulse of Mars via dating of a plume-fed volcano’
https://doi.org/10.1038/s41467-017-00513-8 Additional details on the petrogenetic history of the nakhlite group, including the possible presence of martian bacterial micro-fossils, can be found on the Nakhla page. The specimen of NWA 6148 shown above is a 0.092 g partial slice. The two intact masses composing NWA 5790 are shown below, courtesy of Aziz Habibi.
click on photo above for a magnified view