Date of Award

12-2014

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

Amanda Albright Olsen

Second Committee Member

Edward Grew

Third Committee Member

Brian Olsen

Abstract

Organic acids have been shown to have a significant influence on the dissolution of rocks and minerals. This relationship of enhanced elemental release and rock weathering in the presence of biota is of interest to the geochemical and astrobiological communities because the resulting fluid chemistry can be used as an indicator of environments where life is present. The Jovian moon, Europa, is one of the most likely extraterrestrial locations in our solar system where life could be present. The icy satellite is differentiated into an ice crust, an acidic liquid water ocean, an olivine rich mantle, and likely an iron rich core. The presence of liquid water this far away from the sun suggests that the moon experiences tidal heating that maintains the ocean at a temperature conducive to liquid water. Serpentinization of olivine rich rocks occurs under these pressure and temperature regimes on Earth; therefore the process is thought to be occurring on Europa’s seafloor. The process of serpentinization involves a volume change resulting in deep fracturing of the metamorphosed rock. These resulting crevices are thought to be warm nutrient rich zones that may be potentially habitable. If the seafloor is or was a region of biological activity, it is likely that organic acids produced from the biota would strongly influence the weathering of the serpentinite seafloor resulting in a chemical footprint unique to life.

This study investigated the elemental release behavior of serpentinites in the presence of abiotic-inorganic, abiotic-organic, and biotic-organic acids in order to determine if a chemical signature would be produced and what it would look like. Batch reactor experiments were carried out at 0°C, 22°C, and 62°C in the presence of 16 different acids at pH 2.6 over 28 days of rock-water-acid interaction. Our results show that dissolution in the presence of biotic-organic acids is faster than the dissolution observed in the presence of abiotic-organic or control inorganic acids. Additionally we found that some elements are preferentially released in the presence of biotic-organic acids while others are preferentially released in the presence of abiotic-organic acids and sulfuric acid. Of these elements we found that Ce, Cs, and La are preferentially released only in the presence of the biotic-organic acids and not in the presence of sulfuric acid or the abiotic-organic acids. Therefore we propose that Ce, Cs, and La may be a suitable chemical signature unique to life under Europan conditions.

Column reactor experiments were carried out at ambient pressure and temperature conditions at pH 2.6 in the presence of an abiotic-inorganic, abiotic-organic, and biotic- organic acid in order to better model a natural system. Results from the column reactor experiments are preliminary as the columns continue to run. Thus far we note that Cr, Fe, Sc are preferentially released in the presence of the biotic-organic acid whereas Cu is preferentially released by the abiotic-organic and abiotic-inorganic acids.

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