From Ocean Floor to Stratosphere: Investigating Astrobiologically Relevant Processes and Molecules on Solar System Bodies

Author: Marlin, Theresa

Year: 2026

Degree: Dissertation (Ph.D.)

Advisors: de Kleer, Katherine R.; Cable, Morgan L.

Committee Members: Newman, Dianne K.; Knutson, Heather A.; de Kleer, Katherine R.; Cable, Morgan L.

Option: Geobiology

Abstract

In astrobiology, the quest to understand the origin of life on Earth is often paired with an outward focus on whether life can be found elsewhere in the universe. The most accessible corner of the universe in which to search for extraterrestrial life is our own Solar System —- the planets, their satellites, and the minor bodies present throughout. An examination of the essential elements for life on Earth returns three critical factors: liquid water, complex chemistry, and a source of energy. Searching for these three elements in bodies beyond Earth returns a suite of candidates: the ocean worlds of the outer Solar System. These moons, while too cold to harbor liquid water on their surfaces, are thought to have subsurface liquid water reservoirs which could potentially harbor life. Of particular note are two Saturnian satellites: Enceladus, with predicted hydrothermal activity and water-rock interactions, and Titan, with a dense atmosphere filled with complex organics with potential prebiotic significance. This thesis broadly addresses astrobiological questions on Earth, Enceladus, and Titan via laboratory chemistry and observational astronomy.

(I): Chemical gardens as analogs for hydrothermal vents on ocean worlds. This chapter probes laboratory-synthesized analogs of hydrothermal vents as reaction catalysts with alpha keto acids as reactants under various conditions. NMR spectroscopy results support the formation of prebiotically-relevant molecules including glycine (an amino acid) and maloyl formate (a precursor to alpha keto glutarate (AKG)).

(II): Propyne: determination of physical properties and unit cell parameters under Titan-relevant conditions. Many questions remain about the organic species that are photochemically produced in Titan’s atmosphere. Propyne (CH3CCH) has been detected in gas phase and is a candidate for Titan’s mixed-species ice clouds. This work presents a characterization of solid propyne using Raman spectroscopy, infrared spectroscopy, and X-ray diffraction.

(III):Zonal winds in Titan’s middle atmosphere from a stellar occultation observed with Keck adaptive optics. Winds in Titan’s atmosphere vary seasonally, and stellar occultations present a unique chance to probe them. This work presents spatially-resolved images of the refracted “lightspots" visible around Titan’s limb during an occultation, and discusses the zonal wind profile which best matches the observed data.