Testing hydrothermal Origin-of-Life Theories: implications for early Earth and Enceladus

Helmbrecht, Vanessa (2026): Testing hydrothermal Origin-of-Life Theories: implications for early Earth and Enceladus. Dissertation, LMU München: Faculty of Geosciences

Abstract

The origin of life. We know it happened a long time ago, about 4 billion years ago, to be exact. We know how humanity evolved over time and that water played a key role in our existence. But where did life as we know it begin? Many theories about life’s origin have persisted through time, such as Darwin’s “warm little pond” theory. But hydrothermal vents have emerged as a leading alternative for the site of life’s emergence for many reasons: (1) Hydrothermal vents are natural “bioreactors” with membranes composed of catalytic minerals that often resemble the active centers of modern enzymes. (2) Vent membranes are similar to cell membranes because they separate the interior of the vent from the ocean and harbor a natural proton gradient that drives prebiotic reactions. (3) The interior of vents are porous and made out of interconnected cavities that trap and concentrate molecules. (4) Hydrothermal vents are considered a reliable energy source because they transport hydrogen-enriched fluids from Earth’s interior, fueling CO2 fixation in anaerobic prokaryotes. In summary, hydrothermal vents offer a variety of important features that could have sustained the transition from geochemistry to biochemistry. The last universal common ancestor at the root of the tree of life likely inhabited a similar hydrothermal environment, where it was able to evolve into complex cellular life. The hydrothermal environments that likely facilitated the origin of life on the early Earth are also promising locations in the search for extraterrestrial life in the universe. A possibly habitable candidate is Enceladus, an icy moon of Saturn. Enceladus contains a subsurface water ocean under a global ice sheet and is suspected to host hydrothermal activity on its seafloor. This icy moon gained a lot of attention after NASA’s Cassini mission detected molecular hydrogen, amongst other simple chemicals, in plumes erupting from its south pole. This doctoral thesis aims to investigate prominent origin-of-life theories revolving around the Hadean and Archaean Earth and the icy moon Enceladus. To achieve this goal, laboratory experiments on simulated hydrothermal environments were performed in an anaerobic chamber. Among the explored topics are the RNA-world, the concentration problem, the iron-sulfur world, the reductive acetyl-CoA pathway as a primordial metabolism, and Enceladus as a habitable moon. Collectively, the results of this thesis support hydrothermal vents as plausible hatcheries for the origin of life. Research was conducted over the course of 3.5 years and led to the composition of three first-author papers (Chapter II [published], III [published] and IV [in submission]) and one co-author paper (published), which is added in the Appendix. Furthermore, this thesis provides a foundational framework for future research on the origin of life.

• Item Type: Theses (Dissertation, LMU Munich)
• Subjects: 500 Natural sciences and mathematics; 500 Natural sciences and mathematics > 550 Earth sciences
• Faculties: Faculty of Geosciences
• Language: English
• Date of oral examination: 17. April 2026
• 1. Referee: Orsi, William
• Signature of the printed copy: 0001/UMC 31932