Structural Heat Retention as a Precondition for Life: From Chemical Sufficiency to Structural Necessity

All known forms of life depend on sustained non-equilibrium conditions, maintained through persistent heat gradients that enable metabolism, chemical cycling, and selection. While astrobiological studies frequently emphasize chemical composition and the presence of organic precursors, recent work has demonstrated that chemical sufficiency alone does not guarantee the emergence of life. Building on a structure-first interpretation of heat as a transit problem and magnetic structure as a prerequisite for energetic persistence, this paper argues that life as we know it requires not merely the presence of heat, but the capacity to retain and route heat over biologically relevant timescales. Bodies that exhibit chemical completeness yet lack sufficient structural heat retention—such as small asteroidal systems—remain sterile despite favorable chemistry. This framework establishes structural heat retention as a necessary (though not sufficient) precondition for life and reframes habitability as a problem of energetic persistence rather than chemical inventory.