87,306 research outputs found
Austin Papers: Series II, Part II, 1818-1847
No full textCopy of transcript for a letter from Eliza Martha Westall Austin to Stephen F. Austin thanking him for his letter; offering her condolences for his deceased brother; and discussing Stephen Jr. and clothes she made for Stephen F. Austin
A morphological, mineraloical, geochemical, and isotopic study of a 3.3 Ga photosynthetic microbial mat from Barberton, South Africa
No full textAustin Papers: Series II, Part II, 1818-1847
No full textCopy of transcript for a letter from Eliza Martha Westall Austin to Stephen F. Austin seeking advice on where she and her son, Stephen F. Austin Jr., should live after the death of her husband James E. B. Austin
The nature of bacteriomorphs: biogenicity and its detection N. 2
No full textBreve descrizione del Progetto As the most abundant organisms on Earth since Early Archean, microbes display a wide range of degradation/fossilization possibilities. The discovery of microorganisms living in extreme terrestrial environments makes now plausible the search for life in the ancient deposits of the early Earth with two issues: i) the understanding of the origin of life on Earth, ii) the search for life on Mars and other planetary bodies which experienced environmental settings similar to the ones of early Earth. A crucial aspect in this investigation, however, is the development of criteria for i) a distinction between biogenic and abiogenic structures, and ii) how to distinguish possible contamination products. The planned experiments focus on the recognition of the actual origin of bacteriomorphs and other alleged microbial morphologies. The target is to assess analytical procedures useful for a proper interpretation of alleged biogenic morphologies for which still ambiguous interpretations and the persisting problem of the sample preparation techniques may prevent their use as actual document of biogenic activity
Traces of life on Mars are likely to be very small and very challenging to find
No full textThe volcanic materials at the surface of Mars provide an ideal potential habitat for chemolithotrophic microorganisms that obtain their energy from chemical reactions at the surfaces of minerals and their carbon from inorganic sources in the environment. If life ever appeared on Mars, hydrated environments in the Noachian period could have hosted such life forms. Other types of microorganisms that could possibly have lived at the surface during the Noachian include heterotrophic microorganisms that obtain their carbon source form organic carbon (either the degraded remains of pre-existing organisms or abiogenic sources). The rapid degradation in the environmental conditions at the surface of Mars imply an initially frozen and then dry surface that is unfavourable to the development of more sophisticated microorganisms, such as photosynthesisers. Whereas the latter produce readily recognisable macroscopic to microscopic structures, such as stromatolites and microbial mats, the former do not and their traces are very subtle and challenging to reveal. Fossilised chemolithotrophic microorganisms in littoral volcanic sands from the Early Archaean epoch (the Kitty’s Gap Chert in the Pilbara of Australia, c. 3.45 Ga) represent ideal analogues for eventual Noachian life in martian shallow water sediments. Surficial materials from this period, e.g. sediments and igneous rocks,
have been largely silicified because of high seawater silica saturation and extensive hydrothermal flushing of the environments and the Kitty’s Gap sediments as well as their microorganisms have been silicified. Investigations of the morphological and geochemical biosignatures of the early Archaean microfossils provide valuable information about the methods necessary to identify the fossils. The bulk carbon contents of the Kitty’s Gap Chert is < 0.01% and carbon isotope signatures range from – 25.9 to – 27.8 % . The microfossils are small, dividing coccoids 0.4-0.8 m in diameter that occur in colonial associations of many hundreds of individuals, the colonies reaching sizes of several tens of m in diameter. Because these sediments have been silicified, specific sample preparation involving delicate acid etching is necessary to reveal the microfossils. Although there may be other modes of preservation of microorganisms on Mars, the recent revelations of amorphous hydrothermal silica suggest that Noachian volcanic lithologies may have been silicified, as in the Early Archaean. Future in situ martian missions, such as MSL and ExoMars, carry microscopes but they will not be able to reveal the presence of individual microfossils like the chemolithotrophs of the Kitty’s Gap Chert and probably not even the colonies given the sample preparation necessary (the resolution of the MSL microscope is 12m and that of ExoMars is 4 m). However, Raman spectroscopy could identify carbonaceous phases and GC-MS could provide details of the organic composition, even at low bulk C concentrations. On the other hand, organic molecules in the Early Archaean cherts are very degraded and have generally lost their biogenic specificity. It may therefore not be possible to unambiguously identify martian biosignatures using in situ instrumentation and returning samples to Earth for detailed analysis in a terrestrial laboratory will probably be necessary
Mitchell v. Lewis & Westall (TSTD)
No full text4 items, 15 pages, Brazoria, Cherokee, Harris, Matagorda, Nacogdoches, Nueces Counties, Texas, 1838-1855. Mitchell v. Lewis & Westall. Regarding slave ownership, value. Item 1: District Court of Brazoria County, Texas, fall term, November 3, 1853. Answers to Interrogatory to Solomon Haskell and B. Churchill Jones. Haskell appeared November 15, 1853 in Matagorda County. Stated he had know Mitchell and Lewis since 1838, Westall since 1851. Knew Mitchell in Nacogdoches and Nueces Counties in 1847, Lewis in Nacogdoches and other counties, Westall in Matagorda only. Plaintiff Mitchell residing in Cherokee Co., TX. Stated Martha was of black complexion age about 34, with 2 children, Jim about age 13 and Toby about age 10. Item 2: Matagorda, Nacogdoches Counties, Texas. November 15, 1853. Interrogatories propounded to John Duncan & Robert H. Williams, residents of Matagorda County, Texas. Stated Haskell was overseer for J.R. Lewis and Daniel Rawls in Nacogdoches from 1838 to December 1841. Knew slave Martha well, since 1839. Martha was stout, chunky built woman who had two children. The family had been on the plantation on November 26, 1844 when he last saw her. Rawls represented to him that Martha, her family and certain other Negroes belonged to Robt. F. Mitchell who had put them with Rawls to secure him against a bond in a suit in Nacogdoches County with Mitchell brought by John Dunst. Rawls was to give up Negroes when he was released from the 600, did not know value of the boys. Sworn A. Wadsworth, Notary. Item 3: Harris Co., Texas, September 1856. Execution of Hanson G. Westall, deceased, and Ira R. Lewis. Interrogatory to B. Churchill Jones of Brazoria County, Texas, regarding suit brought by Mitchell against Westall & Lewis since January 1851. Signed Harris & Jones, Attorneys for defendant, Francis Whitlock, Clerk of Harris County, Texas. Permission from Harris County Texas to Brazoria County, Texas to take evidence in case of Mitchell, plaintiff and William G. Hill executor for Hanson G. Westall. Item 4: Brazoria County, Texas, 1855. William B. Ochitree, George McRiley, Jacob Humphrey and Columbus Brown, residents of Cherokee County, Texas. Interrogatory propounded ot John Duncan and Robert H. Williams of Matagorda
Biosignatures in Deep Time
No full textLife on the early Earth inhabited a planet whose environ-ment was vastly different from the Earth of today. An anaerobic and hot early Earth was the birthplace of the first living cells but the wide-spread small-scale physico-chemical diversity provided opportunities for a variety of specialists: alkalophiles, acidophiles, halophiles etc. The earliest record of life has been lost due to plate tectonic recycling and the oldest preserved terranes are quite altered by metamorphism, although they contain weak traces of fossil life. As of ~3.5 Ga, ancient sediments are so well-preserved that a broad diversity of micro-environments and fossil traces of life can be studied, providing a surprising window into communities of microbes that had already reached the evolutionary stage of photosynthesis
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