Chassigny and the nakhlites: Carbon-bearing components and their relationship to Martian environmental conditions

Journal Article · Sat Feb 01 04:00:00 EST 1992 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(92)90100-W· OSTI ID:5195342

Wright, I P; Grady, M M; Pillinger, C T ^[1]

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1. Open Univ., Milton Keynes (United Kingdom)

The carbon and nitrogen inventories of Chassigny and the nakhlites have been investigated by low-resolution stepped combustion; in addition, the contents and isotopic compositions of carbonate minerals have been assessed by the use of an acid-dissolution technique. Low-temperature carbon appears to be from two different sources: one component is present in variable quantities (300-700 ppm) and has {delta}{sup 13}C > {minus}26{per thousand}, consistent with identification as terrestrial organic contamination; the other is isotopically light with {delta}{sup 13}C ca. {minus}36{per thousand}, which is unusual for normal sources of terrestrial contamination. Curiously, the latter material is present in each sample in similar concentrations (45 {plus minus} 15 ppm). Since this level of carbon is too high to be ascribed to a system blank, it is considered that this component is probably indigenous to the meteorites. The low temperature of release of the isotopically light carbonaceous material is testimony to its highly labile nature; it is evidently organic material of some description. The accompanying low-temperature nitrogen also appears to be distributed between two components; but it is not yet possible to establish relationships between the nitrogen and carbon components released below 500C. The meteorites investigated were found to contain 2.5-30 ppm carbon as carbonate, with {delta}{sup 13}C between {minus}5 and +11{per thousand}, and {delta}{sup 18}O between +23 and +29{per thousand}. Variation in {delta}{sup 13}C and {delta}{sup 18}O of the carbonates indicates either a change in conditions during formation of the carbonate minerals or that there may be two distinct carbon sources. There is no evidence in any of the samples analyzed for trapped martian atmospheric gases.

• OSTI ID: 5195342
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 56:2; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ABUNDANCE
ATMOSPHERES
BASALT
CARBON
CARBON ISOTOPES
CARBONATE MINERALS
CHEMICAL COMPOSITION
CHEMISTRY
ELEMENT ABUNDANCE
ELEMENTS
GEOCHEMISTRY
IGNEOUS ROCKS
ISOTOPE RATIO
ISOTOPES
MARS PLANET
METEORITES
MINERALS
NITROGEN
NITROGEN ISOTOPES
NONMETALS
PETROCHEMISTRY
PETROGENESIS
PLANETARY ATMOSPHERES
PLANETS
QUANTITY RATIO
ROCKS
VOLCANIC ROCKS