Sodium Chloride–Water Ionic Systems as a Unified Signature for Earth-Like Exoplanets and Biological Organization

Current approaches to identifying Earth-like exoplanets emphasize the presence of liquid water as a primary criterion for habitability. This paper proposes a refined and more discriminating framework: Earth-like planets are best characterized as self-ionizing water systems, where sodium chloride (NaCl) enables persistent ionic convection across planetary and biological scales. We show that NaCl–water systems naturally generate atmospheric ionization, electromagnetic coupling, and biological compatibility, making them a coherent and detectable signature for life-supporting planets. This same ionic architecture underlies animal physiology and cellular regulation, suggesting a single, scale-independent organizing principle.