Hydrothermal vents versus the "warm little pond": A comparative assessment of energy gradients in prebiotic synthesis and the origin of metabolism

The question of where and how the first living system arose remains the most contested issue in contemporary astrobiology, with the debate running for decades between two schools: the submarine alkaline hydrothermal vent hypothesis and the surface “warm little pond” (hot spring) hypothesis. This article does not attempt to declare a winner. Instead, it introduces a new analytical framework — the topology of the free-energy gradient — which reframes the entire debate as a distinction between a standing vectorial gradient (the chemiosmotic proton and redox gradient across a barrier, characteristic of vents) and a cyclic temporal gradient (alternating wetting and drying, characteristic of ponds). Alongside the framework, a measur-able Free-Energy Coupling Index (FECI) is proposed, scoring each environment along five dimensions: gradient persistence, vectorial coupling, spatial compartmentalization, cyclic condensation, and carbon–energy flux. A comparative synthesis of thermodynamic parame-ters from peer-reviewed literature (2019–2026) shows that vents achieve a high “metabolic bootstrap” score (FECI-M ≈ 0.82), whereas ponds achieve a high “replicative bootstrap” score (FECI-R ≈ 0.79). The central finding is that these two environments are not compet-ing but thermodynamically complementary along the metabolism→replication transition: the vent provides the continuous vectorial gradient required to bootstrap carbon and energy me-tabolism, while the pond provides the cyclic dehydration regime required for polymerization and encapsulation. The article concludes that the origin of life is tied not to a single location but to a sequence of gradient regimes, interpreted here within a morphology of the first cause (prauzrok).