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See Help for more tips. + NASA Center + Publication Year + Availability Options – Item/Media Type  + Journal Article  + NACA Report  + NASA Report  + Preprint  + Technical Report  + Conference Paper  + Reprint Selected Navigations: [Remove] Subject > D-F > Exobiology [x] Publication Year > 1991-2000 [x] Sort results by: NASA Center | Date Added to NTRS | Publication Year There are a total of 580 record(s) matching your query. Sorted by: Date Added To NTRS in Descending order Prev 1 2 3 4 5 6 7 8 9 10 Next >> Investigations into an unknown organism on the martian meteorite Allan Hills 84001 Author(s): Steele, A.; Goddard, D. T.; Stapleton, D.; Toporski, J. K.; Peters, V.; Bassinger, V.; Sharples, G.; Wynn-Williams, D. D.; McKay, D. S. Abstract: Examination of fracture surfaces near the fusion crust of the martian meteorite Allan Hills (ALH) 84001 have been conducted using scanning electron microscopy (SEM) and atomic force microscopy (AFM) and has revealed ... NASA Center: NASA (non Center Specific) Publication Year: 2000 Added to NTRS: 2006-08-02 Document ID: 20040088925 Astrobiology: exploring the origins, evolution, and distribution of life in the Universe Author(s): Des Marais, D. J.; Walter, M. R. Abstract: The search for the origins of life and its presence beyond Earth is strengthened by new technology and by evidence that life tolerates extreme conditions and that planets are widespread. Astrobiologists learn how planets ... NASA Center: Ames Research Center Publication Year: 1999 Added to NTRS: 2006-08-02 Document ID: 20040088896 An intron within the 16S ribosomal RNA gene of the archaeon Pyrobaculum aerophilum Author(s): Burggraf, S.; Larsen, N.; Woese, C. R.; Stetter, K. O. Abstract: The 16S rRNA genes of Pyrobaculum aerophilum and Pyrobaculum islandicum were amplified by the polymerase chain reaction, and the resulting products were sequenced directly. The two organisms are closely related by this ... NASA Center: NASA (non Center Specific) Publication Year: 1993 Added to NTRS: 2006-08-02 Document ID: 20050000499 Recognition of > or = 3850 Ma water-lain sediments in West Greenland and their significance for the early Archaean Earth Author(s): Nutman, A. P.; Mojzsis, S. J.; Friend, C. R. Abstract: A layered body of amphibolite, banded iron formation (BIF), and ultramafic rocks from the island of Akilia, southern West Greenland, is cut by a quartz-dioritic sheet from which SHRIMP zircon 206Pb/207Pb weighted mean ages ... NASA Center: NASA (non Center Specific) Publication Year: 1997 Added to NTRS: 2006-08-02 Document ID: 20040089176 The sequence of Methanospirillum hungatei 23S rRNA confirms the specific relationship between the extreme halophiles and the Methanomicrobiales Author(s): Burggraf, S.; Ching, A.; Stetter, K. O.; Woese, C. R. Abstract: We have determined the sequence of the 23S rRNA from the methanogenic archaeon Methanospirillum hungatei. This is the first such sequence from a member of the Methanomicrobiales. Moreover, it brings additional evidence to ... NASA Center: NASA (non Center Specific) Publication Year: 1991 Added to NTRS: 2006-08-02 Document ID: 20040089506 Sources and sinks for ammonia and nitrite on the early Earth and the reaction of nitrite with ammonia Author(s): Summers, D. P. Abstract: An analysis of sources and sinks for ammonia and nitrite on the early Earth was conducted. Rates of formation and destruction, and steady state concentrations of both species were determined by steady state kinetics. The ... NASA Center: Ames Research Center Publication Year: 1999 Added to NTRS: 2006-08-02 Document ID: 20040142037 Climatic forcing of carbon-oxygen isotopic covariance in temperate-region marl lakes Author(s): Drummond, C. N.; Patterson, W. P.; Walker, J. C. Abstract: Carbon and oxygen stable isotopic compositions of lacustrine carbonate from a southeastern Michigan marl lake display linear covariance over a range of 4.0 Peedee belemnite (PDB) in oxygen and 3.9 (PDB) in carbon. ... NASA Center: NASA (non Center Specific) Publication Year: 1995 Added to NTRS: 2006-08-02 Document ID: 20040089801 A possible prebiotic synthesis of pantetheine, a precursor to coenzyme A Author(s): Keefe, A. D.; Newton, G. L.; Miller, S. L. Abstract: The involvement of coenzyme A in many enzyme reactions suggests that it acted in this capacity very early in the development of life on Earth. Particularly relevant in this regard is its role in the activation of amino acids ... NASA Center: NASA (non Center Specific) Publication Year: 1995 Added to NTRS: 2006-08-02 Document ID: 20050000233 Non-standard amino acid recognition by Escherichia coli leucyl-tRNA synthetase Author(s): Martinis, S. A.; Fox, G. E. Abstract: Recombinant E. coli leucyl-tRNA synthetase was screened for amino acid-dependent pyrophosphate exchange activity using noncognate aliphatic amino acids including norvaline, homocysteine, norleucine, methionine, and ... NASA Center: Goddard Space Flight Center Publication Year: 1997 Added to NTRS: 2006-08-02 Document ID: 20040089262 Polymerization on the rocks: negatively-charged alpha-amino acids Author(s): Hill, A. R. Jr; Bohler, C.; Orgel, L. E. Abstract: Oligomers of the negatively-charged amino acids, glutamic acid, aspartic acid, and O-phospho-L-serine are adsorbed by hydroxylapatite and illite with affinities that increase with oligomer length. In the case of ... NASA Center: NASA (non Center Specific) Publication Year: 1998 Added to NTRS: 2006-08-02 Document ID: 20040172675 Prev 1 2 3 4 5 6 7 8 9 10 Next >> + Back to Top + Sponsored by the NASA Scientific and Technical    Information Program + 2004 Vision for Space Exploration + Freedom of Information Act + NASA Web Privacy Policy and Important Notices + NASA Disclaimers, Copyright Notice,    and Terms and Conditions of Use NASA Official: Calvin Mackey Page Curator: NASA Center for AeroSpace Information (help@sti.nasa.gov) Last Updated: July 5, 2007