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Biosignatures


1. Biosignatures in the Rock Coatings


Student Research Assistant: Ajish Philip
 

In this work we experimentally test the role of silicic acid and bio-chemicals in the formation of desert varnish and other rock coatings. We have developed a protocol in which the rocks are treated with a mixture of silicic acid, sugars, amino acids, metals and clays, under the influence of heat and UV light. This protocol reflects the proposed mechanism of the polymerization of silicic acid with the bioorganic materials, and the laboratory model for the natural conditions under which the desert varnish is formed. Our experiments produced coatings with a hardness and morphology that resemble the natural ones.  These results provide a support for the role of silicic acid and bioorganic materials in the formation of rock coatings. Since the hard silica-based coatings preserve organic compounds in them, they may serve as a biosignature for life, here or possibly on Mars. 

Parts of this project were presented and published:

  1. A. Philip, V. Kolb, W. Zhu, and R. Perry, “The Role of Sugars, Amino Acids, and Silicic Acid in the Formation of Rock Coatings”, 5th Annual University of Wisconsin System Symposium for Undergraduate Research and Creative Activity”, April 28, 2004, Oshkosh, WI, Abstract # PII-12.
  2. A. Philip, V. Kolb, R. Perry, and W. Zhu, “The Role of Sugars, Amino Acids, and Silicic Acid in the Formation of Rock Coatings”, “Posters in the Rotunda 2004, A Celebration of Undergraduate Student Research”, April 27, 2004 State Capitol Rotunda, Madison, WI, Abstract 60, p. 18.
  3. V. M. Kolb, A. I. Philip, W. Zhu, and R. S. Perry, “The Role of Sugars, Amino Acids, and Silicic Acid in The Formation of Rock Coatings”, poster at the Gordon Research Conference on Biomineralization, August 8-13, Colby-Sawyer College, New London, NH, August 8-13 (2004).
  4. V. M. Kolb, A. I. Philip, and R. S. Perry, “Testing the Role of Silicic Acid and Bioorganic Materials in the Formation of Rock Coatings”, in “Instruments, Methods, and Missions to Astrobiology VIII”, R. B. Hoover, G. V. Levin, and A. Y. Rozanov, Eds., SPIE Vol. 5555, pp. 116-125 (2004).
  5. R. S. Perry, V. M. Kolb, A. I. Philip, et al.,“Making Silica Rock Coatings in the Lab: Synthetic Desert Varnish”, in “Astrobiology and Planetary Missions”, R. B. Hoover, G. V. Levin, A. Y. Rozanov, and G. R. Gladstone, Editors, SPIE Vol. 5906, pp. 59060U (1-11) (2005).
  6. V. M. Kolb, M. Bajagic, P. J. Liesch, A. Philip, and G. D. Cody, “On the Maillard reaction of meteoritic amino acids”, in “Instruments, Methods, and Missions for Astrobiology IX” , R. B. Hoover, G. Y. Levin, and A. Y. Rozanov, Eds., SPIE, Vol. 6309, 63090B (1-13) (2006).

 

2. Organic Silicates as Biosignatures

Student Research Assistant: Patrick J. Liesch

  

Amino acids alone or their products of the reactions with sugars (the Maillard products) can be preserved as silicates by two mechanisms.  In the first mechanism, these bio-materials cause polymerization of silicic acid and become entombed in the silicic acid polymer (silica gel).  In this mechanism we would observe only the Si-O-Si bonds in the silica gel.  By the second mechanism, the bio-molecules make chemical bonds with the silicic acid, to create organic silicates, which would have the Si-O-C bonds. We are investigating these two mechanisms by the IR spectroscopy. We have found that upon contact between the meteoritic or other amino acids or their Maillard products with ribose, sodium silicate solution is rapidly transformed into the silica gel.  We have recorded the IR spectra of these gels in KBr and Nujol.  We are concentrating on the region between 1000-1200 cm-1, in which the bands for Si-O-Si and Si-O-C are found. These bands overlap substantially.  We are currently attempting to resolve them by the deuteration of the silica gels that were isolated from the reactions. Deuteration was achieved by heating the gels with D2O at 65oC, or by dissolving the biomolecules in D2O prior to adding them to the sodium silicate solution. Upon deuteration large shifts of the bands in the region of interest towards lower frequencies are observed. Detailed analysis of the spectra is underway and the potential of this IR method for studying organo-silicate biosignatures is now evaluated.

Parts of this project were presented and published:

 

  1. P. J. Liesch and V. M. Kolb, “Organic Silicates as Potential Biosignatures”, 7th Annual UW System Symposium for Undergraduate Research and Creative Activity”, UW-Stout, Menomonie, WI, May 5, 2006, Abstract PO44.
  2. P. J. Liesch and V. M. Kolb, “Organic Silicates as Potential Biosignatures”, Posters in the Rotunda, A Celebration of Undergraduate Student Research, Capitol Rotunda, Madison, WI, April 25, 2006, Abstract 63.
  3. V. M. Kolb and P. J. Liesch, “Organic Silicates as Biosignatures”, Astrobiology, 6, 223 (2006).
  4. V. M. Kolb, M. Bajagic, P. J. Liesch, A. Philip, and G. D. Cody, “On the Maillard reaction of meteoritic amino acids”, in “Instruments, Methods, and Missions for Astrobiology IX” , R. B. Hoover, G. Y. Levin, and A. Y. Rozanov, Eds., SPIE Vol. 6309, 63090B (1-13) (2006).
  5. V. M. Kolb and P. J. Liesch, “Role of amino acids and their Maillard mixtures with ribose in the biosilicification process”, in “Instruments, Methods, and Missions for Astrobiology IX”, R. B. Hoover, G. Y. Levin, and A. Y. Rozanov, Eds., SPIE Vol. 6309, 63090T(1-8) (2006).

 


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