Racemization of amino acids in sediments from saanich inlet, british columbia.

In sediments spanning the last 9000 years from Saanich Inlet L enantiomers of amino acids are most abundant, but the percentages of D enantiomers increase with age, apparently because of partial racemization. Of the amino acids measured, glutamic acid and alanine show the greatest degree of racemization; leucine, isoleucine, and valine show the least.

Carbon isotopic studies of organic matter in precambrian rocks.

Reduced carbon in early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa is isotopically similar (the average value of delta(13)C(PDB) is -28.7 per mil) to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts (Theespruit formation) is anomalously heavy (the average value of delta(13)C(PDB) is -16.5 per mil). This discontinuity may reflect a major event in biological evolution.

Submarine seep of carbon dioxide in norton sound, alaska.

Earlier workers have described a submarine gas seep in Norton Sound having an unusual mixture of petroleum-like, low-molecular-weight hydrocarbons. Actually, only about 0.04 percent of the seeping gas is hydrocarbons and 98 percent is carbon dioxide. The isotopic compositions of carbon dioxide (delta(13)C(PDB) = -2.7 per mil) and methane (delta(13)C(PDB) = -36 per mil, where PDB is the Peedee belemnite standard) indicate that geothermal processes are active here.

Search for porphyrins in lunar dust.

Evidence for porphyrins was obtained in the Apollo 11 bulk sample of lunar dust by fluorescence spectrometry and analytical demetallation. The indicated porphyrins showed major fluorescence excitation at 390 nanometers. Abundance was about 10(-10) gram of porphyrin per gram of dust. Similar pigments were found in exhaust products from tests of a lunar descent engine. The similarity of results suggests that most if not all of the indicated porphyrin aggregate of the lunar sample probably was synthesized from rocket fuel during the landing of the lunar module. These compounds may be the product of a novel high-temperature synthesis of cosmochemical interest.

Amino acids indigenous to the murray meteorite.

Analysis of the Murray meteorite, a type II carbonaceous chondrite, has led to the identification of 17 amino acids. For seven of the amino acids nearly equal amounts of the D and L isomers are present, and 11 of the amino acids are not found in protein. These results suggest that these amino acids, like the amino acids of the Murchison meteorite, are extraterrestrial in origin.

Carbon, carbides, and methane in an apollo 12 sample.

Total carbon in the Apollo 12 sample 12023 fines was 110 micrograms per gram of sample with a carbon isotopic abundance delta(13)C (relative to the Pee Dee belemnite standard) of +12 per mil. Hydrolysis of the fines with deuterium chloride yielded undeuterated methane along with deuterated hydrocarbons, thus confirming the presence of 7 to 21 micrograms of carbon per gram of sample as carbide and about 2 micrograms of carbon per gram of sample as indigenous methane. After vacuum pyrolysis of the fines to 1100 degrees C the following gases were detected in the relative abundance: carbon monoxide carbon dioxide methane. Variations of the delta(13)C value with the pyrolysis temperature indicated the presence of carbon with more than one range of isotopic values. The observed delta(13)C value of +14 per mil for lunar carbide is much higher than that of carbide in meteorites. These results suggest that lunar carbide is either indigenous to the moon or a meteoritic contribution that has been highly fractionated isotopically.

Petroleum associated with polymetallic sulfide in sediment from gorda ridge.

A sediment sample, impregnated with asphaltic petroleum and polymetallic sulfide, was dredged from the southern end of Gorda Ridge (the Escanaba Trough) off northern California, within the offshore Exclusive Economic Zone of the United States. The molecular distributions of hydrocarbons in this petroleum show that it was probably derived from terrestrial organic matter in turbidite sediment filling the Escanaba Trough. Hydrothermal activity at the Gorda Ridge spreading center provided the heat for petroleum formation and was the source of fluids for sulfide mineralization.

Search for organic compounds in the lunar dust from the sea of tranquiblity.

A sample of lunar dust was examined for organic compounds. Carbon detected in concentrations of 157 micrograms per gram had a delta(13)C per mil (PDB) value of + 20. Treatment with hydrochloric acid yielded hydrocarbons of low molecular weight, suggesting the presence of carbides. The gas chromatogram of the acylated and esterified derivatives of the hydrolyzate was similar to that obtained for the Pueblito de Allende meteorite. There were no detectable amounts of extractable high-molecular-weight alkanes, aromatic hydrocarbons, isoprenoid hydrocarbons, normal alkanes, fatty acids, amino acids, sugars, or nucleic acid bases. Traces of porphyrins were found, perhaps arising from rocket exhaust materials.

Carbon isotope systematics of individual hydrocarbons in hydrothermal petroleum from Escanaba Trough, northeastern Pacific Ocean.

We submitted individual aliphatic and polycyclic aromatic hydrocarbons in samples of hydrothermal petroleum from Escanaba Trough to compound specific isotope analysis to trace their origins. The carbon isotope compositions of the alkanes and polycyclic aromatic hydrocarbons (means -27.5 and -24.7%, respectively) reflect a primarily terrestrial organic matter source.

Potential effects of gas hydrate on human welfare.

For almost 30 years. serious interest has been directed toward natural gas hydrate, a crystalline solid composed of water and methane, as a potential (i) energy resource, (ii) factor in global climate change, and (iii) submarine geohazard. Although each of these issues can affect human welfare, only (iii) is considered to be of immediate importance. Assessments of gas hydrate as an energy resource have often been overly optimistic, based in part on its very high methane content and on its worldwide occurrence in continental margins. Although these attributes are attractive, geologic settings, reservoir properties, and phase-equilibria considerations diminish the energy resource potential of natural gas hydrate. The possible role of gas hydrate in global climate change has been often overstated. Although methane is a "greenhouse" gas in the atmosphere, much methane from dissociated gas hydrate may never reach the atmosphere, but rather may be converted to carbon dioxide and sequestered by the hydrosphere/biosphere before reaching the atmosphere. Thus, methane from gas hydrate may have little opportunity to affect global climate change. However, submarine geohazards (such as sediment instabilities and slope failures on local and regional scales, leading to debris flows, slumps, slides, and possible tsunamis) caused by gas-hydrate dissociation are of immediate and increasing importance as humankind moves to exploit seabed resources in ever-deepening waters of coastal oceans. The vulnerability of gas hydrate to temperature and sea level changes enhances the instability of deep-water oceanic sediments, and thus human activities and installations in this setting can be affected.

Nonprotein amino acids in the murchison meteorite.

Twelve nonprotein amino acids appear to be present in the Murchison meteorite. The identity of eight of them has been conclusively established as N-methylglycine, beta-alanine, 2-methylalanine, alpha-amino-n-butyric acid, beta-amino-n-butyric acid, gamma-amino-n-butyric acid, isovaline, and pipecolic acid. Tentative evidence is presented for the presence of N-methylalanine, N-ethylglycine, beta-aminoisobutyric acid, and norvaline. These amino acids appear to be extraterrestrial in origin and may provide new evidence for the hypothesis of chemical evolution.