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  • 1
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    Release of noble gases and nitrogen from grain-surface sites in lunar ilmenite by closed-system oxidation (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Noble gases and nitrogen were extracted from a 100 to 150 microns ilmenite separate from lunar soil 71501 by closed system stepped heating in approx. 10 torr O2 at 300 C, 400 C, 500 C, 600 C and 630 C, followed by stepped pyrolysis at ten temperatures between 680 C and approx. 1500 C. The five oxidation steps together liberated approx. 65% of the total He-4, 45% of the Ne-20, 23% of the N-14 and Ar-36, 12% of the Kr-84 and 8% of the Xe-132 in the sample; Ne-20/Ar-36 and Ne-20/Ne-22 ratios agree with the solar wind composition experiment, and Kr-84/Ar-36 and Xe-132/Ar-36 are within approx. 10% of Cameron's estimates for the sun and solar wind. The remaining gases, released above 630 C by pyrolysis, are strongly fractionated with respect to the SWC-Cameron solar wind elemental composition. Large concentrations of fractionated noble gases in grain interiors, their virtual absence in the relatively unfractionated surface gas reservoir, and the high N/noble gas ratio all imply that most of the solar wind noble gases initially implanted in grain surfaces are eventually lost by diffusion. Loss limits can be estimated by considering two given scenarios. It is concluded tat approx. 70 to 97% or more of the Ar implanted in 71501 ilmenite grains has diffusively escaped.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on Past and Present Solar Radiation: The Record in Meteoritic and Lunar Regolith Material; p 22-23
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  • 2
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    Noble gas patterns in the atmospheres of Mars and Earth: A comparison via the SNC meteorites (1985)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: Noble gas and nitrogen compositions in the glassy phase of the EETA 79001 shergottite correspond closely with Viking measurements. This direct evidence for the origin of the SNC meteorites on Mars, and for trapping of an unfractionated sample of Martian atmospheric gases in the 79001 glass, provides a reasonable basis for comparing the Martian and terrestrial atmospheres with more precision than that afforded by the Viking data set. Results are that, with one exception, elemental and isotopic compositions of nonradiogenic Martian noble gases are similar to those in the Earth's atmosphere; relatively small isotopic discrepancies in Kr and perhaps Xe may be attributable to different degrees of mass fractionation of a common parent reservoir. The anomaly is in Ar composition, where Martian Ar-36/AR-38 approx. 4 is strikingly lower than the values near 5.3 that characterize both the Earth and major meteoritic gas carriers. Although a primordial Martian ratio of 5.3 could in principle be altered by some planet specific process (e.g., cosmic ray spallation of surface materials) operating over geologic time, one has not been found that works.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Terrest. Planets: Comp. Planetology; p 2
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  • 3
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    Evidence for a secular variation in the C-13/C-12 ratio of carbon implanted in lunar soils (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A curve of delta(C-13) vs delta(N-15) for lunar soils and breccias shows that the previously recorded 30% change in delta(N-15) is associated with a change in delta(C-13). The correlation represents concurrent changes in the isotope ratios of both elements at their source, and does not result from maturation effects or nonselective sample contamination. A computation of the relative production rates of C-13 and N-15 shows that spallation reactions in the sun could produce the observed ratio of the delta(C-13) to delta (N-15) variations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 50; 1, Oc; Oct. 198
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  • 4
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    Carbon, hydrogen and nitrogen isotopes in solvent-extractable organic matter from carbonaceous chondrites (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: CCl4 and CH3OH solvent extractions were performed on the Murray, Murchison, Orgueil and Renazzo carbonaceous chondrites. Delta-D values of +300-+500% are found in the case of the CH3OH-soluble organic matter. The combined C, H and N isotope data makes it unlikely that the CH3OH-soluble components are derivable from, or simply related to, the insoluble organic polymer found in the same meteorites. A relation between the event that formed hydrous minerals in CI1 and CM2 meteorites and the introduction of water- and methanol-soluble organic compounds is suggested. Organic matter soluble in CCl4 has no N, and delta-C-13 values are lower than for CH3OH-soluble phases. It is concluded that there either are large isotopic fractionations for carbon and hydrogen between different soluble organic phases, or the less polar components are partially of terrestrial origin.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 46; Jan. 198
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  • 5
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    Solar composition noble gases in the Washington County iron meteorite (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A sample of the Washington County iron meteorite is analyzed for its light noble gases by a combustion technique in two steps at 1160 C. The ratio of trapped to spallogenic noble gases in the sample was high enough to allow the resolution of trapped and spallogenic components in both combustion steps. The He:Ne:Ar elemental ratios in the trapped component are comparable to present-day solar-wind ratios. The (Ne-20)/(Ne-22) ratio, while subject to some uncertainty due to possible variation in either the spallation or the trapped component between the two steps, is in the range 13.3 + or 0.5, also comparable to present-day solar wind. Unless the Washington County iron formed by some unique process in a solar-wind-irradiated regolith, the fact that the trapped gas is of solar composition has implications with regard to the compositional history of the solar wind, to conditions in the early solar nebula during grain formation or accretion, and to primordial helium in the earth.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters (ISSN 0012-821X); 70; 1 Se
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  • 6
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    The case for a Martian origin of the shergottites - Nitrogen and noble gases in EETA 79001 (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Nitrogen and noble gases have been measured in samples of a glass inclusion and its surrounding basaltic matrix in an Antarctic shergottite meteorite (EETA 79001). The nitrogen component was found trapped in the glass, but not the matrix, having a value of delta 15-N = +190 per mil. Ratios between abundances of Ar-40 and N-14, N-15 and N-14 in the glass are consistent with the dilution of a Martian atmospheric component. The trapped noble gases in the glass are similar to elemental and isotopic compositions measured in Mars atmosphere by the Viking lander, and are in general agreement with previous measurements. It is suggested that a sample of Martian atmosphere has been caught in the EETA 79001 glass, and that other shergottite, nakhilite, and chassignite meteorites with similar features probably also originated on Mars. A table is presented which lists the abundances of nitrogen and the noble gases found in the non-glassy matrix and in the EETA 79001 glass.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters (ISSN 0012-821X); 69; 2 Au
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  • 7
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    Does application of the Rosiwal Principle to lunar soils require that concentrations of solar-wind-implanted species be grain-size independent (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A reconsideration of the application of the Rosiwal Principle to lunar soils indicates a flaw in arguments put forth previously by Criswell (1975). Specifically, by introducing a boundary condition which must exist at the lunar surface, it is shown that concentrations of solar-wind-implanted species showing a dependence on grain size may be able to develop in soils at concentration levels below those required for saturation of grain surfaces. As a result, observed grain-size-dependent concentrations of solar-wind species in lunar soils do not necessarily require the exposure time scales or solar-wind fluxes deduced from the arguments of Criswell.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 34; 1, Fe; Feb. 197
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  • 8
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    Light elements in lunar soils revisited - Carbon, nitrogen, hydrogen and helium (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Based on combined data from F2-stripping and step-wise heating experiments, it is found that about 30-40% of carbon and nitrogen in submature and mature lunar soils resides in the outermost 0.1 micron of grains, presumably in the amorphous coatings that are known to be present. The remainder of carbon and nitrogen resides in composite particles such as agglutinates and microbreccias, within which C and N are distributed in a roughly uniform way. Helium shows much larger variations in its distribution between grain surfaces and interiors, with helium yield related to ilmenite content of the soil. The depth distribution of solar wind hydrogen is not readily resolvable by the stripping technique.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 17, 1980 - Mar 21, 1980; Houston, TX
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  • 9
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    Characterization of lunar nitrogen components (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Rocks of known and disparate cosmic-ray ages are analyzed to find the spallation production rate of N-15. A soil breccia of known formation age was analyzed for its bearing on the antiquity of the isotopically light component. Further stepwise heating analysis of soils shed further light on occurrences of the components. Lunar soil samples were etched slightly by fluorine, revealing significant differences in isotopic ratios between carbon on grain surfaces and bulk carbon; the surface carbon is not retained during agglutinate formation. Etching revealed that about 25% of the total nitrogen resides on the surface of grains; the nitrogen is isotopically heavy. Etching also revealed about 50% of helium in soils residing below the readily etched outermost 1% of soil grain surfaces.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 15, 1976 - Mar 19, 1976; Houston, TX
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  • 10
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    Shock-induced devolatilization of calcite (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Experimental measurements of the release adiabats by Vizgirda (1981) indicate that substantial vaporization takes place upon release from shock pressures of 37 GPa for calcite and 14 GPa for aragonite. The present investigation includes the first controlled partial vaporization experiments on calcite. The experiments were conducted to test the predictions of the release adiabat experiments. The quantities of the gaseous species produced from shocked calcite and their carbon and oxygen isotopic compositions were determined, and the shock-induced effect on the Mn(2+) electron spin resonance spectrum in the shock-recovered calcite was observed. On the basis of the obtained results, it is concluded that shock stresses at the 17-18 GPa level give rise to volatilization of 0.03-0.3 (mole) percent of calcite to CO2 and CO. The devolatilization of calcite occurs at low pressure at significantly lower entropy densities than predicted on the basis of thermodynamic continuum models.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 61; 1; Nov. 198
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