Lunar and Planetary Science XXXI sess79.pdf

Friday, March 17, 2000 ASTROBIOLOGY: METEORITES 8:30 a.m. Room C

Chairs: B. P. Weiss A. H. Treiman

Golden D. C. Ming D. W. * Schwandt C. S. Lauer H. V. Jr. Socki R. A. Morris R. V. Lofgren G. E. McKay G. A. Inorganic Formation of Zoned Mg-Fe-Ca Carbonate Globules with Magnetite and Sulfide Rims Similar to Those in Martian Meteorite ALH84001 [#1799] We show here experimental evidence that the carbonate-sulfide-magnetite assemblage in Martian meteorite ALH84001 may result from simple inorganic processes.

Thomas-Keprta K. L. Clemett S. J. * Bazylinski D. A. Kirschvink J. L. McKay D. S. Wentworth S. J. Vali H. Gibson E. K. Statistical Analyses Comparing Prismatic Magnetite Crystals in ALH84001 Carbonate Globules with Those from the Terrestrial Magnetotactic Bacteria Strain MV-1 [#1683] Here we use rigorous mathematical modeling to compare ALH84001 prismatic magnetites with those produced by terrestrial magnetotactic bacteria, MV-1. We find that this subset of the Martian magnetites appears to be statistically indistinguishable from those of MV-1.

Koziol A. M. * Carbonate and Magnetite Parageneses as Monitors of Carbon Dioxide and Oxygen Fugacity [#1424] The stable coexistence of siderite with other key minerals, such as graphite or magnetite, is only possible under certain restrictive conditions of CO2 and O2 fugacity. Carbonate parageneses in Mars meteorite ALH 84001 are analyzed.

Bell M. S. * McHone J. F. Kudryavtsev A. McKay D. S. Raman Mapping of Carbonates in ALH84001 Martian Meteorite [#1909] Raman mapping is utilized to constrain the spatial distribution of fine scale shock effects previously reported from TEM studies. These effects include residual oxides from the formation of magnetite in carbonate and incipient amorphous silica and orthopyroxene.

Weiss B. P. * Kirschvink J. L. Baudenbacher F. J. Vali H. Macdonald F. A. Wikswo J. P. Reconciliation of Magnetic and Petrographic Constraints on ALH84001? Panspermia Lives On! [#2078] New results from scanning SQUID magnetic microscopy place a strict constraint on the maximum temperature (< 40 C) ALH84001 experienced since before formation of the carbonate blebs.

Treiman A. H. * Heterogeneity of Remnant Magnetism in ALH84001: Petrologic Constraints [#1225] Pyrrhotite in ALH84001 trapped a natural remnant magnetism, in random orientations, that has never seen T > 40°C. The NRM was trapped late in the meteorite’s history, after its major brecciation, and probably after deposition of the carbonate globules.

Thomas-Keprta K. L. * Wentworth S. J. McKay D. S. Gibson E. K. Field Emission Gun Scanning Electron (FEGSEM) and Transmission Electron (TEM) Microscopy of Phyllosilicates in Martian Meteorites ALH84001, Nakhla, and Shergotty [#1690] Here we document the occurrence of phyllosilicates and alteration phases in three martian meteorites, suggest formation conditions required for phyllosilicate formation and speculate on the extent of fluid:rock interactions during the past history of Mars. Lunar and Planetary Science XXXI sess79.pdf

Brearley A. J. * Hydrous Phases in ALH84001: Further Evidence for Preterrestrial Alteration and a Shock-induced Thermal Overprint [#1203] Rare K-bearing phlogopitic micas have been found in veins and pockets in carbonate fragments in ALH84001. The micas appear to have formed from preexisting low temperature hydrous alteration products by reaction with the carbonate during shock-induced heating.

Sephton M. A. Gilmour I. * Ever Repeating Circles — The Origin of PAHs in Meteorites [#1703] Molecular level isotopic measurements of aromatic compounds in meteorites indicate that a specific interstellar environment and process may be responsible for the formation of a significant proportion of meteoritic aromatic organic mat

Stephan T. * Jessberger E. K. Polycyclic Aromatic Hydrocarbons in Allan Hills 84001 — Implications from Time-of-Flight Secondary Ion Mass Spectrometry Analyses [#1326] TOF-SIMS investigation of PAHs on fracture surfaces of ALH 84001 showed no correlation between PAHs and carbonates. Analysis of terrestrial PAHs with TOF-SIMS offers no way to discern biogenic PAHs from those in carbonaceous meteorites or ALH 84001.

Botta O. * Ehrenfreund P. Glavin D. P. Cooper G. W. Kminek G. Bada J. L. A Cometary Origin of the Amino Acids in the Orgueil Meteorite? [#1398] A reexamination of a piece of the Orgueil meteorite revealed that its amino acid composition is strikingly different to two other carbonaceous chondrites, suggesting different parent bodies. A cometary origin for Orgueil would be one possibility.

Cooper G. Horz F. O’Leary A. * Chang S. Shock Modification of Organic Compounds on Carbonaceous Chondrite Parent Bodies [#1616] Samples of mixed organic compounds, embedded in a matrix of the Murchison meteorite, were subject to a simulated hypervelocity impact. The molecular compositions of products were then analyzed to determine the degree of survival of the original compounds.

Grymes R. Tsairides C. * NAI Education and Public Outreach [#1791] The NAI’s Education and Public Outreach Office is committed to building a strong partnership with each member institute to develop a comprehensive interest in educating the public and global community on the activities of the institute and the field of Astrobiology.