Organic chemistry and mineral interactions in the solar system

Goodyear, Michael David (2013). Organic chemistry and mineral interactions in the solar system. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000d5bf

Abstract

The objective of this project was to develop methods to detect meteoritic organic compounds in situ, and to detelmine whether any associations exist between specific classes of compound and co-located minerals, thus indicating a possible common origin. Carbonaceous chondrites, (which comprise a small proportion of meteorites), contain a few per cent of organic material, heterogeneously distributed within their structure, the major part being macromolecular ("insoluble organic material", lOM). Model compounds were covalently bonded to "molecular tags", atoms or groups not normally present in meteorites, enabling easier detection against background signals when using analytical methods suitable for use in situ, such as Raman spectroscopy or SEM. Also, extra functionality was introduced to model compounds by ozone treatment, allowing a greater density of tags to be attached. Following development work with terrestrial models, meteorite samples were exposed to ozone, but oxalic acid was formed instead of the expected oxygenated IOM derivative. To determine if this result was due to an effect of the minerals present, whole rock samples and demineralised IOM were analysed, both before and after exposure to ozone. Isolated IOM behaved differently from that still in situ. Fresh samples ofIOM were isolated (using two literature methods), and their reactions and properties compared. The evidence obtained indicated that the structure of IOM had been modified on isolation, and that the modifications caused by the two methods were different. This shows that any data generated from isolated IOM does not necessarily directly relate to organic material still present within a meteorite. Using the data obtained in this study, and that previously reported, two-component models for the structure of lOM, and scenarios for its formation, were discussed.

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