Autogenous Melt- The Size Gate for Planetary Molten Interiors
Year: 2025
Type: article
Abstract: Octomorphic V: Autogenous Melt — A Geometric Sizing Law for Planetary Interiors Abstract:We propose a novel mechanism,"autogenous melt," to explain the transition from solid to molten planetary interiors. Within the Octomorphic Framework, which defines stability via guardrails on lattice strain handoffs (ΔL ≤ 0.25, Coherence TB ≥ 0.60), we demonstrate that gravitational self-compression in sufficiently massive bodies forces a geometric crisis. Beyond a critical threshold, elastic strain handoffs become impossible, violating the guardrails. The system's only lawful path to restore coherence is to pump out lattice defects, a process that is intrinsically self-heating. This drives a phase transition to a mixed solid-liquid state, where flow relieves the geometrically forbidden strain. We quantify this threshold with a dimensionless Bulk Compaction Number, 𝒞 = Gρ²R²/K_M^eff, and identify a melt gate at 𝒞_gate ≈ 0.17 for silicates. The model successfully explains the internal states of Solar System bodies—including the molten cores of Earth and Mercury, the solidification of Mars, and the externally forced melt of Io—and makes falsifiable predictions for the core states and magnetic fields of rocky exoplanets. This work reframes planetary melting as a necessary outcome of information and coordination limits in condensed matter, rather than a purely thermal phenomenon. The "Size Gate" for Molten Planets Why do some planets have molten cores while others are solid? We propose a new law: melting is a geometric necessity for large rocky bodies. In our "Octomorphic" model, planetary matter must obey strict rules for how it handles internal strain. As a planet grows, gravity's pressure forces it to break these rules. The only way to avoid systemic failure is to partially melt. This "autogenous melt" is a self-regulating process, driven not by primordial heat but by the geometry of strain itself. We define a "Compaction Number" (𝒞) that predicts this transition. It accurately classifies planets in our Solar System and predicts that most large, rocky exoplanets ("Super-Earths") will have liquid cores and strong magnetic dynamos. New theory: Big rocky planets must have molten insides. It's a law of geometry, not just heat. As planets get massive, their own gravity forces their internal structure to break its own "rules." The only way out? Melting. This "self-melting" explains why Earth is molten inside but Mars is mostly solid, and predicts many alien worlds will have magnetic fields. #PlanetaryScience #Physics #Exoplanets
Author: Simpson, Brian
Language: English
Topic: Astro and Planetary Science
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7090856313
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