Dissertation/Thesis Abstract

Investigations into the Production and Reactions of Perchlorate on Mars, Its Effects on Organic Compounds, and the Implications in the Search for Life
by Liu, Dongyu, Ph.D., Tufts University, 2020, 140; 27837297
Abstract (Summary)

The research presented here addresses the mechanisms for photochemical formation of perchlorate (ClO4-) from sodium chlorite (ClO2-) and sodium chlorate (ClO3-) under both ambient and humid Mars conditions, the effects of chloride (Cl-) and oxychlorine salts (NaClO2, NaClO3 and NaClO4) on amino acid degradation under Mars conditions, and the critical parameters necessary for bacteria to survive in the harsh Mars environment. The perchlorate production rates from NaClO2, NaClO3 were measured. Titanium dioxide (TiO2) was added to the sample to evaluate its role in perchlorate production. The effects of humidity and UV radiation wavelength on perchlorate production were compared. The chemical changes during perchlorate formation were quantitively analyzed with ion chromatography to help better understand the reaction pathways. The degradation of three amino acids (glycine, proline and tryptophan) under Mars conditions were studied. A degradation mechanism for glycine and proline was proposed to explain the opposite effects the salts have under ambient Mars and humid Mars conditions. It was also demonstrated that tryptophan degradation under Mars conditions followed a different mechanism due to the indole ring present compared to glycine and proline. Preliminary studies on the ability of E. coli, and Eucapsis sp. to survive on Mars were carried out, varying parameters such as salinity and nutrients. Additionally, the effects of three different Mars soil simulants (MMS-1 F, MGS-1 and JSC-Mars-1A) on bacterial growth were investigated, with MMS-1 F soil leachate found to be the most suitable for Eucapsis growth. Culturing conditions and analytical methods were optimized for the bacteria studied.

Indexing (document details)
Advisor: Kounaves, Samuel P.
Commitee: Sykes, Charles E., Utz, Arthur L., Hecht, Michael H.
School: Tufts University
Department: Chemistry
School Location: United States -- Massachusetts
Source: DAI-B 81/12(E), Dissertation Abstracts International
Subjects: Chemistry, Geochemistry, Analytical chemistry
Keywords: Amino acid degradation, Bacteria, Mars, Mars soil simulants, Oxychlorine, Perchlorate
Publication Number: 27837297
ISBN: 9798645495435
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