Differentiating indigenous and exogenous soluble organic matter in CM carbonaceous chondrites

Hourston, Holly Isabella (2025) Differentiating indigenous and exogenous soluble organic matter in CM carbonaceous chondrites. MSc(R) thesis, University of Glasgow.

Abstract

It is accepted that life, as we understand it, must be carbon-based. The study of extraterrestrial organic molecules is a venture into understanding why our planet is unique in hosting its diverse range of life, and which others may be capable of hosting life. One theory suggests that the building blocks of life were brought to Earth by meteorites from the asteroid belt. More specifically, CM carbonaceous chondrites are particularly carbon and water-rich samples which have already been found to contain prebiotic molecules such as amino acids. In the early solar nebula, secondary processes such as aqueous alteration modified the meteorite parent bodies, and as a result, also altered the organic content, water content and volatile element abundances in the meteorites that bombarded the early Earth and the inner Solar System.

The work presented in this thesis aims to firstly identify the organic molecules present in two CM chondrite samples of differing extents of aqueous alteration- a more extensively aqueously altered sample (namedNWA 10853, a CM2.0) and a less aqueously altered sample (Murchison, CM2.5). This will be achieved using gas chromatography-mass spectrometry in a meteoritics organics identification protocol developed at the University of Glasgow. The meteorite NWA 10853 is presented with its first 3D-rendering through X-ray computed tomography, and its elemental composition outlined through SEM-EDS study.

Secondly, this thesis discusses meteorite contamination risks and sources of contamination in the samples used, and subjects the detected compounds to several contaminant identification checks. We present this alongside an evaluation of potential methods for improving the confidence rate with which geochemists in meteoritics can determine the source of an organic molecule as extra-terrestrial or terrestrial in origin. Lastly, the link between the extent of aqueous alteration and the abundance of organics in CM chondrites is discussed, and we begin explore to which extent aqueous alteration of parent bodies affects the variability in organic content within different meteorites.

The results and analysis undertaken in this study concludes that the long-chain organic compounds intrinsic to the sample of NWA 10853 studied are nonanoic acid, decanoic acid, dodecanoic acid, myristic acid, pentadecanoic acid and palmitelaidic acid. Those intrinsic to the sample of Murchison studied are nonanoic acid, tetradecanol, and myristic acid. This work also recommends that NWA 10853 is reclassified from CM2.0 to a CM2.1 carbonaceous chondrite, based on results of XCT, SEM-EDS, and its organics abundances, which all suggest less extensive alteration than suggested by optical study.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Additional Information: Supported by funding from SAGES, University of Glasgow, and the Astrobiology Society of Britain.
• Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences; Q Science > QB Astronomy; Q Science > QC Physics; Q Science > QE Geology
• Colleges/Schools: College of Science and Engineering > School of Geographical and Earth Sciences
• Funder's Name: SAGES, University of Glasgow, Astrobiology Society of Britain
• Supervisor's Name: Hallis, Dr. Lydia and Daly, Dr. Luke
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85130
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 23 May 2025 09:01
• Last Modified: 27 May 2025 08:29
• Thesis DOI: 10.5525/gla.thesis.85130
• URI: https://theses.gla.ac.uk/id/eprint/85130