<p>The class of meteorites called carbonaceous chondrites are examples of material from the solar system which have been relatively unchanged from the time of their initial formation. We investigate the carbonaceous chondrite subclasses CI, CM, CR, CV, and CO, which contain high levels of water and organic material, including amino acids. These subclasses span petrologic types 1 through 3, indicating the degree of internal chemistry undergone by the meteoritic parent body. The goal of this thesis is two-fold: to obtain a comprehensive view of amino acid abundances and relative frequencies in carbonaceous chondrites, and to recreate these patterns via thermodynamic computational models.</p> <p>We collate available amino acid abundance data for a variety of meteorites to identify patterns in total abundance and relative frequencies. We consider only a set of 20 proteinogenic alpha-amino acids created via a specific chemical pathway called Strecker synthesis. We plot abundances of individual amino acids for each subclass, as well as total abundances across all subclasses. We see a predominance in abundance and variety of amino acids in the CM and CR subclasses, which contain concentrations of amino acids greater by several orders of magnitude than other carbonaceous subclasses. These subclasses correspond to an aqueous alteration temperature range of 200 deg. C to 400 deg. C. Within the CM2 and CR2 meteorites, we identify trends in the relative frequencies of amino acids in preparation for computational modeling.</p> <p>Now having a baseline observed amino acid abundance plot, we recreate both the total amino acid abundance pattern as well as the relative frequency of amino acids within the CM2 chondrite subclass using computational models. We use thermodynamic theory of Gibbs free energies to calculate the output of amino acids in a meteoritic parent body assuming chemical equilibrium and some set of initial concentrations of organic material. Our model recreates abundance patterns in the temperature range 200 deg. C to 400 deg. C, ~10<sup>5</sup> parts-per billion (ppb), and the temperature range 400 deg. C to 500 deg. C, ~10<sup>2</sup> ppb. Our model does not fit well between temperatures of 150 deg. C to 200 deg. C. Our current model assumes a uniform composition of initial chemical reactants; likely an inhomogeneous composition would be a more accurate physical representation of a parent body. In addition, we match relative frequencies to observed frequencies for each amino acid in the CM2 subclass to well within an order of magnitude.</p> / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/13531 |
| Date | 10 1900 |
| Creators | Cobb, Alyssa K. |
| Contributors | Pudritz, Ralph E., Physics and Astronomy |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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