Martian ShergottiteIgneous stony meteorite with a Martian origin consisting mainly of plagioclase (or a shocked glass of plagioclase composition) and pyroxene. They are the most abundant type of SNC meteorites and the type member is the Shergotty meteorite, which fell in India in 1865. Shergottites are igneous rocks of volcanic or Click on Term to Read More
(depleted, permafic, primitive mantle-derived melt)
Purchased June, 2002
no coordinates recorded Three fragments constituting a single fresh stone meteoriteWork 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 and partially covered in a glossy, bubbly, black fusion crustMelted exterior of a meteorite that forms when it passes through Earth’s atmosphere. Friction with the air will raise a meteorite’s surface temperature upwards of 4800 K (8180 °F) and will melt (ablate) the surface minerals and flow backwards over the surface as shown in the Lafayette meteorite photograph below. Click on Term to Read More were found in the Morroccan Sahara. The combined weight of the three meteorite fragments was determined to be 49 g. A 1.8 g sample of the meteorite was provided to G Hupé who sent a sample both to the University of Washington (A. Irving and S. Kuehner) for petrographic analysis, and to the Carnegie Institute (D. Rumble III) for O-isotope analysis. It was ascertained that NWA 5789 is a rare primitive martian meteoriteOver 30 of the meteorites found on Earth almost certainly came from Mars (see http://www.imca.cc/mars/martian-meteorites.htm and http://www2.jpl.nasa.gov/snc/). All but one belongs to the group known as SNC meteorites, which includes the shergottites, nakhlites, and chassignites. SNC meteorites contain minerals that crystallized within the past 1.35 to 0.15 Ga, making them Click on Term to Read More. Thereafter, the remaining quantity of NWA 5789 was purchased by Chladni’s Heirs (S. Ralew and M. Altmann).
Northwest Africa 5789 is a slightly friable meteorite with a permafic composition. A terrestrial analog for this meteorite is limburgite, a rock type found in a volcanicIgneous rock that forms from cooling magma on the surface of a planet or asteroid. quarry in Limburg, Germany. Limburgite is a rapidly cooled, alkaline, sometimes vesicularVesicles appear in nature when they are produced within lava (extrusive aphanitic igneous rock) whose dissolved gases come out of solution (are released) due to the drop in pressure during an eruption. The resulting lava solidifies around the gas bubbles capturing their shape inside and outside the rock. Vesicles do Click on Term to Read More basaltic lavaHot molten or semifluid rock derived from a volcano or surface fissure from a differentiated and magmatically active parent body. Click on Term to Read More, primarily composed of olivineGroup of silicate minerals, (Mg,Fe)2SiO4, with the compositional endpoints of forsterite (Mg2SiO4) and fayalite (Fe2SiO4). Olivine is commonly found in all chondrites within both the matrix and chondrules, achondrites including most primitive achondrites and some evolved achondrites, in pallasites as large yellow-green crystals (brown when terrestrialized), in the silicate portion Click on Term to Read More and augiteHigh-Ca clinopyroxene, (Ca,Mg,Fe)SiO3, that occurs in many igneous rocks, particularly those of basaltic composition. In order to be considered augite, the clinopyroxene must contain 20 to 45 mol % of calcium (Wo20 - 45). An important and unique Martian meteorite is NWA 8159, that has been classified as an augite basalt. Click on Term to Read More. This rock type is often associated with hydrated minerals such as kaersutite. The reservoir from which the parent magmaMolten silicate (rock) beneath the surface of a planetary body or moon. When it reaches the surface, magma is called lava. Click on Term to Read More for NWA 5789 was derived had a composition that was depleted in incompatible elements, to which 2% olivine was added (Irving et al., 2010; Treiman and Filiberto, 2014).
Northwest Africa 5789 is almost identical in bulk composition, petrography, and mineralInorganic 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 chemistry, and similar in texture to the martian meteorite Yamato 980459, an olivine-websterite, which crystallized from the most primitive martian melt known (Gross et al., 2010). However, there are textural differences between the two meteorites related to differences in their cooling rate. In Y-980459, it was shown by Greshake et al. (2004) that ascent of the magma to the surface resulted in rapid quenching that suppressed the formation of plagioclaseAlso 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 and produced a glassy mesostasisLast material to crystallize/solidify from a melt. Mesostasis can be found in both chondrules, in the matrix around chondrules, and in achondrites as interstitial fine-grained material such as plagioclase, and/or as glass between crystalline minerals. Click on Term to Read More. In contrast, NWA 5789 experienced slower cooling as it ascended from higher to lower pressures, and the mesostasis formed crystalline plagioclase with radiating sprays of clinopyroxene, spinelMg-Al oxide, MgAl2O4, found in CAIs., ilmeniteTi-Fe oxide, TiFeO3, found in achondrites, lunar mare basalts, and shergottites. Ilmenite forms as a primary mineral in mafic igneous rocks. It crystallizes relatively early out of a magma before most of the other minerals, and as a result, the heavier crystals of ilmenite precipitate to the bottom of the magma Click on Term to Read More, FeS, and silicaSilicon dioxide, SiO2. laths. Another difference between the two meteorites which is more indicative of separate parental source regions on Mars is the high-siderophile elementSubstance 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 content and Os isotopes; the HSE in Y-980459 is higher, while the 187Os/188Os ratio is lower. Furthermore, Hoffmann et al. (2010) determined that significant differences exist between their respective magnetic signatures.
As with Y-980459 (Fo84–86), NWA 5789 is thought to represent a Mg-rich, primitive mantleMain 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 in which olivine megacryst cores have a Mg# in equilibriumTerm 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 with the melt of the bulk rock composition (Fo84.4 compared to the equilibrium value of Fo85.5) (Gross et al., 2011). Olivines in both meteorites are virtually identical, present as mm-sized yellow-green megacrysts containing the highest known Mg# values among martian meteorites. In addition, smaller phenocrysts of olivine and pyroxeneA class of silicate (SiO3) minerals that form a solid solution between iron and magnesium and can contain up to 50% calcium. Pyroxenes are important rock forming minerals and critical to understanding igneous processes. For more detailed information, please read the Pyroxene Group article found in the Meteoritics & Classification category. Click on Term to Read More in equilibrium are scattered throughout a fine-grained groundmass composed of pigeoniteLow-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, chromiteBrownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups. Click on Term to Read More, pyrrhotiteIron sulfide group of minerals whose composition ranges widely between its end members pyrrhotite (Fe7S8) whose crystal structure is monoclinic, and troilite (FeS) whose crystal structure is hexagonal. Its general formula is Fe1−xS (where x = 0 to 0.17). The troilite phase is found mainly in meteorites and in the Click on Term to Read More and mesostasis. It was suggested that the two meteorites might originate from the same or similar source magmas, with NWA 5789 crystallizing more slowly in a thicker section of the melt.
Based on pyroxene crystallizationPhysical or chemical process or action that results in the formation of regularly-shaped, -sized, and -patterned solid forms known as crystals. Click on Term to Read More in NWA 5789, it was shown that the cores formed at high pressure conditions, consistent with the crustOutermost layer of a differentiated planet, asteroid or moon, usually consisting of silicate rock and extending no more than 10s of km from the surface. The term is also applied to icy bodies, in which case it is composed of ices, frozen gases, and accumulated meteoritic material. On Earth, the Click on Term to Read More or upper mantle, while the mesostasis formed at lower pressures, on or near the surface (Gross et al., 2011). This difference in pressure amounts to ~10 kbar or a difference in depth of 85 km, indicating an extended crystallization history that was completed when the magma erupted onto the surface. Temperatures of the magma at depth for both Y-980459 and NWA 5789 were calculated to have been 1300–1400°C, and were formed in reducedOxidation 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 redoxOxidation 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 conditions (oxygen fugacityUsed 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 near the iron–wüstite buffer). Modeling of the composition of both Y-980459 and NWA 5789 by Filiberto and Dasgupta (2012) suggests their parent magmas separated from a primary mantle source region at a pressure of 1.2 (±0.1) GPa and temperature of 1540 (±20) °C, consistent with a relatively shallow depth of ~100 km. This temperature is at the high end of the range calculated for the average mantle temperature during the Noachian period (4.5–3.6 b.y. ago) of 1450 [±80] °C, and they attribute this to a thermal anomaly.
It was calculated that both NWA 5789 and Y-980459 had a pre-atmospheric diameter of <10 cm, and they exhibit similar CRE ages of 1.0 (±0.2) m.y. This CRE age is indistinguishable from that of at least 7 other depleted olivine-phyric shergottite falls, all of which evidently represent a common ejection event on Mars (Nishiizumi et al., 2011). Cosmic ray exposure ages have now been determined for many martian meteorites, and Mahajan (2015) compiled a chart based on the reported CRE ages for 53 of them. He concluded that together these 53 meteorites represent 10 distinct impact events which occurred 0.92 m.y., 2.12 m.y., 2.77 m.y., 4.05 m.y., 7.3 m.y., 9.6 m.y., 11.07 m.y., 12.27 m.y., 15 m.y., and 16.73 m.y.—see his chart here. It was argued that NWA 5789 was launched from Mars during the 0.92 m.y.-old impact event. In a subsequent review based on multiple criteria, Irving et al. (2017 [#2068]) made a new determination of the number of separate launch events associated with the known (101 at the time of their study) martian meteorites. They speculate that the number could be as few as twenty, and suggest that NWA 5789 and at least 18 other depleted (predominantly olivine-phyric) shergottitesIgneous stony meteorite with a Martian origin consisting mainly of plagioclase (or a shocked glass of plagioclase composition) and pyroxene. They are the most abundant type of SNC meteorites and the type member is the Shergotty meteorite, which fell in India in 1865. Shergottites are igneous rocks of volcanic or Click on Term to Read More were ejected 1.1. m.y. ago in a common impact event unique from the others.
A new systematic classification method was invoked for the shergottites by Irving et al. (2010). They utilized a bulk chemical diagram comparing the CaO content with the Mg#, and established three separate categories encompassing all possible values: maficOne of the two broad categories of silicate minerals, the other being felsic, based on its magnesium (Mg) and/or iron (Fe) content. Mafic indicates silicate minerals that are predominantly comprised of Mg and/or Fe.The term is derived from those major constituents: Magnesium + Ferrum (Latin for iron) + ic (having Click on Term to Read More, permafic, and ultramaficTerm used for silicate minerals with cations predominantly Mg and/or Fe. Mafic minerals are dominated by plagioclase and pyroxene, and also contain smaller amounts of olivine. Click on Term to Read More (see 41st LPSC, #1547 ). In addition, they combined the resulting designation with the existing terminology pertaining to trace element abundances and isotopic systematics: enriched, intermediate, and depleted. Next, these designations are combined with the established meteorite group name: mafic or diabasic shergottite (formerly ‘basaltic’ shergottite), olivine-phyric shergottite, poikilitic shergottite (formerly ‘lherzolitic’ shergottite), nakhliteOne 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, chassigniteThe 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, or orthopyroxeniteA rock composed primarily of orthopyroxene. Non-terrestrial orthopyoxenites include diogenites and a single martian meteorite, ALH 84001, that was found in the Allan Hills region of Antarctica in 1984. ALH 84001 is a cumulate rock consisting of 97% coarse-grained, Mg-rich orthopyroxene, with small amounts of plagioclase, chromite, and carbonate. It Click on Term to Read More. Under this scheme the primitive martian magmatic rock NWA 5789 is classified as a depleted permafic olivine-phyric shergottite.
The martian rover ‘Spirit’ has identified alkaline volcanic rocks at Gusev craterBowl-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 which are geochemically consistent with limburgite, and which may characterize highlands terrane on Mars (Kochemasov, 2006). The specimen of NWA 5789 shown above is a sub-gram fragment. The mesmerizing photos below, kindly provided by Chladni’s Heirs, show different views of this unique martian meteorite.
∗ Recent geochemical research on the martian basalts has led to new petrogenetic models and classification schemes.read more >>
Photo courtesy of Chladni’s Heirs
Photo courtesy of Chladni’s Heirs
Photo courtesy of Chladni’s Heirs
Photo courtesy of Chladni’s Heirs
Photo courtesy of Chladni’s Heirs
Photo courtesy of Chladni’s Heirs