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  • LUNAR AND PLANETARY EXPLORATION  (14)
  • Enzyme digestion
  • 2010-2014
  • 1990-1994  (5)
  • 1985-1989  (6)
  • 1975-1979  (4)
  • 1950-1954
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  • 1
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    Hydrogen and carbon isotopic composition of volatiles in Nakhla: Implications for weathering on Mars (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Gases were collected at 120, 200, 300, 415, and 600 and 850 C. Hydrogen yields for the 600 and 850 C aliquots were measured separately and then the gases were combined for isotopic analysis. CO2 samples collected at the two lowest temperature steps amounted to less than 0.5 mu mole and were not analyzed isotopically. Excluding the 120 C temperature step, the bulk delta D of the sample was + 187 percent. Delta D values increase from -91 percent in the 120 C step to +518 percent in the 315 to 850 C step. The hydrogen content is greatest in the 120 C step and is roughly constant in the 200, 300, and 415 C aliquots. Between 415 C and 850 C, the yield drops off considerably. From 850 C to 950 C, virtually no H2 and only minor CO2 (less than 1 mu mole) were extracted. Using the isotopic analysis from the 300, 415, 600, and 850 C temperature collections, the bulk delta C-13 sub (PDB) is 0.0 percent. The heaviest component (delta C-13 sub (PDB) of +29 percent) was collected between 300 and 415 C. The release of hydrogen at the low temperatures reported here is consistent with the breakdown of the phases that constitute the alteration product between approx. 250 and 650 C. Although not as high as the present Martian atmosphere, the high delta D values are consistent with a Martian origin for the meteorites in question.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Workshop on the Martian Surface and Atmosphere Through Time; p 165-166
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  • 2
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    High D/H ratios of water in magmatic amphiboles in Chassigny: Possible constraints on the isotopic composition of magmatic water on Mars (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: The D/H ratios of kaersutitic amphiboles contained in magmatic inclusions in the Shergottites Nakhlites Chassignites (SNC) meteorite Chassigny using the ion microprobe were measured. A lower limit on the delta(D(sub SMOW)) of the amphiboles is +1420 +/- 47 percent. Assuming Chassigny comes from Mars and the amphiboles have not been subject to alteration after their crystallization, this result implies either that recycling of D-enriched Martian atmosphere-derived waters into the planetary interior has taken place, or that the primordial hydrogen isotopic composition of the interior of Mars differs significantly from that of the Earth (delta(D(sub SMOW)) approximately 0 percent). In addition, the measurements indicate that the amphiboles contain less than 0.3 wt. percent water. This is much lower than published estimates, and indicates a less-hydrous Chassigny parent magma than previously suggested.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z; p 1493-1494
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  • 3
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    Sources of Na for the Io atmosphere (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: The physics and geology of Io have been extensively studied, but there has been little discussion of the chemistry. Relatively little is known about Io chemistry, but there are constraints. Further, it will be a long time before improvements will result from direct observation, given the severe difficulties with the Galileo mission. Via laboratory simulation experiments, plausible thermochemical and photochemical processes which determine the nature and amounts of surface constituents of Io are explored. The well-known density of Io shows that the planet overall is rocky. Because the orbit of Io is well within the magnetosphere of Jupiter and because Io only has a thin, transient SO2 atmosphere, the surface is continually sputtered with magnetospheric ions. Complex processes ionize and accelerate the Io surface atoms to keV and MeV energies. Remarkably, only S, O, and Na ions were found by Voyager. Sputtering also produces an atomic cloud of Na and S (O not observable) with a trace of K. Both gaseous and solid SO2 are known from spectroscopic studies. A trace of H2S and possibly CO2 are present. Geologic features are interpreted in terms of elemental S, but there is no direct evidence for this constituent. We thus have a rocky planet which does not have rocks on the surface. Our general goal is to understand the cycling of Na, S, and O through the crust and atmosphere on present-day Io and to understand how Io evolved to this state. A specific objective was to determine the phases on the surface which are the source of the Na in the atmosphere of Io.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Twenty-fourth Lunar and Planetary Science Conference. Part 1: A-F; p 229-230
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  • 4
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    A search for presolar organic matter in meteorite (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The D/H ratios and the C-13/C-12 ratios of acid-insoluble organic matter of 4 meteorites, Ochansk (H4), Plainview (H5), Gladstone (H6) and Odessa (IA), were measured. delta-D values for hydrogen extracted by stepwise combustion were negative, down to -280 deg/infinity. delta-C-13 values were also negative except in the case of the carbon coming off at the highest temperature steps for Plainview and Odessa meteorites. The concentrations of C-13-rich carbon were 3-5 orders of magnitude smaller than those found in Murchison meteorite, suggesting that relic grains of stellar condensates were mostly destroyed in the meteorites examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 12; 73-76
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  • 5
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    Mercury - Thermal emission at radio wavelengths. I - 3.3- and 28-mm observed brightness temperatures and periodicities therein (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The thermal radio emission from Mercury at 3.3 mm and 28 mm was measured over a period of several years, and the results of a statistical analysis of the data are reported. The disk-average brightness temperature is reported as a function of longitude, and other periodicities are reported. The range of values of the thermophysical parameters is constrained by comparing the data with models.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 62; 448-457
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  • 6
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    Ca isotope fractionation on the moon (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Ca has been measured in a lunar soil in order to establish the presence of isotopically mass-fractionated components. Ca was extracted by a series of water leaches after the soils were 'activated' by brief exposures to fluorine gas. The O2 obtained by this fluorination is found to have delta (O-18) of +21 per mil and to be, therefore, significantly mass-fractionated. Ca obtained in the leaches was analyzed using the double-spike technique. Very small Ca isotope fractionation is found in the leaches of this soil of up to 1 per mil per mass unit difference. The small Ca effects are in marked contrast to the measured delta (O-18) for the same sample and to large effects observed in many soils for oxygen, silicon, sulfur, and potassium. The data on Ca provide stringent constraints on models which attempt to explain the isotope mass-fractionation effects in lunar soils.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 7
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    Correlated Si isotope anomalies and large C-13 enrichments in a family of exotic SiC grains (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A hypothesis is presented to the effect that the distinctive morphological characteristics and comparatively simple Si isotope systematics identify the platy SiC crystals as a genetically related family, formed around a single isotopically heterogeneous presolar star on an association of related stars. The enrichments in C-13 and the Si isotope systematics of the platy SiC are broadly consistent with theoretical models of nucleosynthesis in low-mass, carbon stars on the ASG. The Si isotope array most plausibly reflects mixing between (Si-28)-rich material, inherited from a previous generation of stars, and material enriched in Si-29 and Si-30, produced in intershell regions by neutron capture during He-burning. The absence of a correlation between the Si and C isotopic compositions of the SiC suggests either episodic condensation of SiC, extending over several thermal pulses, in the atmosphere of a single star, or the derivation of the SiC from several stars characterized by different rates of C-13 production.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters (ISSN 0012-821X); 107; 4-Mar
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  • 8
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    Isotopic and molecular analyses of hydrocarbons and monocarboxylic acids of the Murchison meteorite (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The monocarboxylic acids and hydrocarbons of the Murchison meteorite (CM2) were isolated for isotropic analysis. The nonvolatile hydrocarbons were analyzed as crude methanol and benzene-methanol extracts and also after separation by silica gel chromatography into predominantly aliphatic, aromatic, and polar hydrocarbon fractions. The volatile hydrocarbons were obtained after progressive decomposition of the meteorite matrix by freeze-thaw, hot water, and acid treatment. Molecular analyses of the aromatic hydrocarbons showed them to comprise a complex suite of compounds in which pyrene, fluoranthene, phenanthrene, and acenaphthene were the most abundant components, a result similar to earlier analyses. The polar hydrocarbons also comprise a very complex mixture in which aromatic ketones, nitrogen, and sulfur heterocycles were identified. The monocarboxylic acids, aliphatic, aromatic, and polar hydrocarbons, and the indigenous volatile hydrocarbons were found to be D-rich. The deuterium enrichment observed in these compounds is suggestive. In two separate analyses, the delta-D values of the nonvolatile hydrocarbons were observed to increase in the following order: aliphatic-aromatic-polar. This finding is consistent with an early solar system or parent body conversion of aromatic to aliphatic compounds as well as the suggestion of pyrolytic formation of aromatic from aliphatic compounds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 56; 11; p. 4045-4058.
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  • 9
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    S-process krypton of variable isotopic composition in the Murchison meteorite (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Data are reported which, for the first time, permit the derivation of the full isotopic spectrum of s-process krypton with reasonable precision. It is shown that this s-Kr in a residue from the Murchison meteorite did not originate in one single s-process but rather is a mixture of contributions from stellar environments where the density of free neutrons was not the same. The astrophysical conditions under which this krypton was produced were distinct from those that have been invoked to explain the solar system s-process abundance. Similar to the C-13-rich carbon component in an aliquot of the same residue, the s-process Kr from different astrophysical sites has retained its identity during the accumulation and subsequent history of the meteorite.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 332; 700-702
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  • 10
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    The effect of pressure and excitation energy on the isotopic fractionation in the formation of ozone by discharge of O2 (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Isotopic fractionation processes in the formation of O3 by discharge (at 20 kV and 3 MHz) of O2 in a fused silica container at 77 K are investigated experimentally, with a focus on the effects of changes in the isotopic abundances in the predischarge O2, the O2 pressure, and the excitation energy on the isotope abundances in the postdischarge O2 and O3. The results are presented in extensive tables and graphs and characterized in detail, and good general agreement is found with data obtained using 60-kHz excitation (Yang and Epstein, 1987). It is shown that O-17 and O-18 enrichment of the residual O2 (when the predischarge gas is enriched) or of the O3 (when atmospheric isotope abundances are used) can occur independently of one another. It is inferred that the rate of anharmonic predissociation of vibrationally hot O3 depends on the symmetry and mass of the O3 molecules. The significance of the present findings for studies of anomalous oxygen isotope abundances in meteorites is indicated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 51; 2019-202
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