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Meinschein, W. G.

Publications and source records attributed to Meinschein, W. G..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of the insectivorous bats in the region of Carlsbad, New Mexico

The structures and C-13 contents of individual hydrocarbons extracted from bat guano found in the Carlsbad region of New Mexico are analyzed in order to elucidate details of the carbon flow in the plant-insect-bat ecosystem. Carbon isotopic analyses indicate that equivalent numbers of plants with C3 and C4 photosynthetic pathways occupy the feeding area of the bats, which supports alfalfa and cotton as well as native plants. The molecular composition of the guano is consistent with an origin in two distinct populations of insects with different feeding habits, one of which may graze predominantly on crops. It is also pointed out that isotopic analyses of more ancient guano deposits may be useful in characterizing prevalent vegetation and climate of earlier periods.

Des Marais, D. J.↗
NASA NTRS1980

The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of insectivorous bats in the region of Carlsbad, New Mexico

The structures and C-13 contents of individual alkanes extracted from bat guano found in the Carlsbad region of New Mexico can be related to both the photosynthetic pathways of the local plants and the feeding habits of the insects that support the bats. Carbon isotopic analyses of the 62 most important plant species in the Pecos River Valley, the most significant feeding area for the Carlsbad bats, reveal the presence of 29 species with C3 photosynthesis and 33 species, mostly grasses, with C4 photosynthesis. Although the abundances of nonagricultural C3 and C4 plants are similar, alfalfa and cotton, both C3 plants, constitute over 95 per cent of the crop biomass. The molecular composition of the bat guano hydrocarbons is fully consistent with an insect origin. Two isotopically distinct groups of insect branched alkanes were discerned. These two groups of alkanes derived from two chemotaxonomically distinct populations of insects possessing distinctly different feeding habits. It is likely that one population grazes predominantly on crops whereas the other population prefers native vegetation. This and other isotopic evidence supports the notion that crop pests constitute a major percentage of the bats' diet.

Desmarais, D. J.↗
NASA NTRS1977

Variation in stable carbon isotopes in organic matter from the Gunflint Iron Formation

Results are presented for an isotopic analysis of the kerogen separated from 15 samples of the Gunflint Iron Formation, Ontario, and the conformably overlying Rove Formation. Reasons for which the Gunflint Iron Formation is suitable for such a study of a single Precambrian formation are identified. The general geology of the formation is outlined along with sample selection, description, and preparation. Major conclusions are that the basal Gunflint algal chert and shale facies are depleted in C-13 relative to the chert-carbonate and taconite facies, that differences in the delta C-13 values between Gunflint facies correlate with marked differences in their biological source materials as evidenced by their respective microbiotas, that the anthraxolites are anomalously depleted in C-13 relative to the kerogen of their encompassing cherts and shales, and that the effects of igneous intrusion and concomitant thermal alteration are shown by a marked loss of C-12 at the contact. The demonstration that not all kerogens are isotopically alike stresses the importance of facies data to the interpretation of C-13/C-12 ratios of ancient organic matter.

Barghoorn, E. S.↗
NASA NTRS1976

Agglutinates and carbon accumulation in Apollo 17 lunar soils

A critical review of maturity with respect to the abundance of implanted solar wind elements (SWE) in lunar soils indicates: (1) that the Rosiwal Principle has limited applicability in determining implantation of SWE in lunar soils, and (2) that despite a depletion of SWE in agglutinitic glass, agglutinates are enriched in SWE due to the presence of buried surfaces of numerous clasts within agglutinates. A statistical analysis of published data of several Apollo 17 soils indicates that the abundance of carbon and, by analogy, the abundance of other SWE are correlatable with the agglutinate content and the mean grain size of lunar soils. Microscopic examination of more than 5000 grains of agglutinates in polished thin sections reveals a wide range of variability in the mineralogy, grain size distribution, degree of recycling, etc., of the clast population in agglutinates. This indicates that the volume-correlated SWE content of agglutinates may vary and need not be constant.

Basu, A.↗
NASA NTRS1975

Integrated investigation of the mixed origin of lunar sample 72161,11

The comminution-agglutination model and the solar-wind implantation-retention model are used to postulate the origins of the particulate components of lunar sample (72161,11), a submillimeter fraction of a surface sample for the dark mantle regolith at LRV-3. Grain-size analysis was performed by wet sieving with liquid argon, and analyses for CO2, CO, CH4, and H2 were carried out by stepwise pyrolysis in a helium atmosphere. The results indicate that the present sample is from a mature regolith, but the agglutinate content is only 30% in the particle-size range between 90 and 177 microns, indicating an apparent departure from steady state. Analyses of the carbon, methane, and hydrogen concentrations in size fractions larger than 149 microns show that the volume-correlated component of these species increases with increased grain size. It is suggested that the observed increase can be explained in terms of mixing of a dominant local population of coarser agglutinates having high carbon and hydrogen concentrations with an imported population of finer agglutinates relatively poor in carbon and hydrogen.

Basu, A.↗
NASA NTRS1975

Evolution of carbon isotopes, agglutinates, and the lunar regolith

Apollo 17 light-mantle soils and Apollo 15 Apennine Front soils are compared with respect to isotopic enrichment of C-13 and the maturity of the site. Analyses of soil-size fractions indicate that while the carbon concentration on particle surfaces remains relatively constant with increasing soil maturity, total surface-correlated carbon increases due to increasing total soil surface area. The role of agglutinates in the incorporation of surface-correlated carbon into aggregate grains is examined; agglutinates contain a major percentage of the carbon found in mature soil, and the volume-correlated carbon component in agglutinates apparently continues to increase after the surface-correlated carbon concentrations have reached a constant value. Constraints that may limit the carbon concentration in lunar soils to a value not greater than 300 micrograms/g are considered.

Desmarais, D. J.↗
NASA NTRS1974

The distribution in lunar soil of hydrogen released by pyrolysis

The hydrogen contents of various Apollo 15 rocks and Apollo 15 and 16 soil particle types and sieve fractions have been determined by the pyrolysis method. The Apollo 15 crystalline rocks analyzed release very little hydrogen (approximately 6 micromoles H/g sample). The mineral, glass, and light-colored breccia fragments in the soils contain approximately 5, 30, and 10 micromoles H/g sample, respectively. The dark breccias and glassy agglutinates examined have much higher hydrogen contents (60 and 110 micromoles H/g sample). For soil particle diameters less than 105 microns, hydrogen content increases linearly with particle surface area per particle mass. The calculated grain surface average concentrations of hydrogen in the Apollo 15 and 16 soils fall short of experimentally determined saturation values by a factor of 20. The volume-correlated component of hydrogen in a soil increases with the maturity of the soil.

Desmarais, D. J.↗
NASA NTRS1973

Techniques for the analysis of gases sequentially released from lunar samples

Description of two methods for the analysis of light gases that are sequentially evolved from 2 to 10 mg of lunar sample. A hydrofluoric acid hydrolysis of lunar material is achieved by repeated exposure of the sample to hydrogen fluoride. In the second technique, gases are evolved from lunar samples by the stepwise heating of these samples to 1400 C. The gases evolved by either hydrolysis or pyrolysis are analyzed in a gas chromatographic system using a helium ionization detector. The sensitivities of this detector for the gases, as analyzed, range from 20 picograms/sec for hydrogen to 0.2 picogram/sec for carbon dioxide.

Desmarais, D. J.↗
NASA NTRS1973

The distribution in lunar soil of carbon released by pyrolysis

The carbon contents of various lunar soil particle types and sieve fractions of Apollo 15 and 16 samples have been determined by the pyrolysis method. The mineral, glass, and high-grade breccia fragments in the soils examined contain relatively low amounts of carbon (approximately 8, 25, and 25 microg C/g sample respectively in 149-250 micron grains). Most low-grade breccias and all agglutinates examined have high carbon contents (approximately 52 and 80 microg C/g sample respectively), and agglutinate abundance is indicative of the carbon content and maturity of a soil. The distribution of carbon with respect to particle size in mature soils generally reveals a minimum in carbon content at about 100 micron particle diameter. At smaller particle diameters, carbon content is directly proportional to particle surface area and therefore increases with the ratio (surface area)/(particle mass). A model relating the cycle of comminution and aggregation of soil particles to the redistribution of surface implanted carbon is developed.

Desmarais, D. J.↗