Engineering topics

Chang, Sherwood

Publications and source records attributed to Chang, Sherwood.

59 records · Page 4

NASA NTRS1989

Isotopic characteristics of simulated meteoritic organic matter. I - Kerogen-like material

Carbonaceous residues from a variety of laboratory syntheses yield release patterns for C and H isotopes during stepwise combustion that fail to mimic the striking patterns characteristic of meteoritic kerogen-like residues that otherwise superficially resemble them. It seems likely that the meteoritic material comprises a complex mixture of substances having different origins and/or synthesis conditions.

Kerridge, John F.↗

NASA NTRS1988

Deuterium exchange during acid-demineralisation

Isotopic analyses of residues prepared by demineralization of the Murchison meteorite using D-labelled reagents provide evidence for measurable exchange of H-isotopes between residue and reagents. Precise quantification of this effect is precluded by substantial inhomogeneity of the meteoritic organic matter. A conservative estimate of the degree of exchange is 3-5 percent of the H pyrolyzable as H2O. This could affect the shape of the curve defining D release as a function of temperature, but does not change conclusions previously drawn concerning the nature of the bulk D enrichment of insoluble organic matter in meteorites.

Kerridge, John F.↗

NASA NTRS1988

Laboratory investigations of Mars - Chemical and spectroscopic characteristics of a suite of clays as Mars soil analogs

A model system of Mars soil analog materials (MSAMs) was prepared, and the properties of these clays, such as chemical composition, surface-ion composition, water adsorption isotherms, and reflectance spectra, were examined. The results of these studies, performed along with simulations of the Viking Labeled Release Experiement using MSAMs, indicate that surface iron and adsorbed water are important determinants of clay behavior, as evidenced by changes in reflectance, water absorption, and clay surface reactions. The paper discusses the relevance of these results to the two major questions raised by prior explorations of Mars: has there ever been abundant water on Mars, and why is the iron found in the Martian soil not readily seen in the reflectance spectra of the surface?

Banin, Amos↗

NASA NTRS1987

Isotopic characterisation of kerogen-like material in the Murchison carbonaceous chondrite

Data on isotopic composition of C, H, and N in insoluble organic fraction from the Murchison CM chondrite were used to discriminate between different theories for the origin of prebiotic organic material in the early solar system. Considerable isotopic variability was found among the samples and attributed to kerogen-like organic fraction. Three to four different isotopic components, two of them of polycyclic aromatic nature, were tentatively identified. Aliphatic moieties in the kerogen-like material, most of the polycyclic aromatic network, and extractable amino acids were found to carry a highly D-enriched component believed to have originated in an interstellar molecular cloud. A least part of the polycyclic aromatic fraction may also represent interstellar material.

Kerridge, John F.↗

NASA NTRS1977

Chemical Evolution and the Origin of Life: Bibliography 1975

This bibliography is the sixth annual supplement to the comprehensive bibliography on the same subject which was published in Space Life Sci.We would like to draw attention to a recently published cumulative bibliography on this same subject: Biochemical Origin of Life: Chemistry and Life. Soil and Water and Its Relationship to Origin of Life. MR - Studies of Prebiotic Polypeptides. Energy, Matter, and Life. Prospects for the Future Orientation of Scientific Research. Photochemical Formation of Self Sustaining Coacervates. Photochemical Formation of Self-Sustaining Coacervates. Comparative Study of Abiogenesis of Cysteine and Other Amino Acids Catalyzed by Various Metal Ions. Protein Structure and the Molecular Evolution of Biological Energy Conversion. Origin of Life. Clues from Relations Between Chemical Compositions of Living Organisms and Natural Environments. Shock Synthesis of Amino Acids II.', Origins of Life 6(1-2). Dynamics of the Chemical Evolution of Earth's Primitive Atmosphere. The Mechanisms of Amino Acids Synthesis by High Temperature Shock-Waves. Theory of Chemical Evolution. Physical Foundations of Probability of Biogenesis.

West, Martha W.↗