issmelting

Issmelting is a neologism used to describe a hypothetical or speculative melting-like transition of ice or ice-like solids under uncommon conditions, such as microgravity, extreme confinement, or atypical pressure–temperature combinations. The term is not part of standard physical chemistry nomenclature and remains largely confined to informal discussions and speculative writing.

Proposed mechanisms for issmelting include confinement-induced melting, where nanoscale pores or thin films suppress the solid phase relative to bulk; pressure fluctuations or transient heating that locally raise internal energy; the presence of impurities or interfaces that alter phase boundaries; and irradiation or energetic input that destabilizes crystal lattices. In microgravity, peculiar phase equilibria and reduced sedimentation can influence the stability of thin ice layers or hydrate structures, potentially yielding melting-like responses at temperatures near or below 0°C.

In practice, issmelting is controversial and not widely adopted in peer-reviewed literature. It is often discussed alongside established concepts such as melting point depression, surface melting, and confinement-induced phase transitions. Researchers emphasize that conventional thermodynamics and experimental evidence should guide interpretations, and that any claim of a distinct issmelting mechanism requires reproducible measurements.

Potential detection methods include calorimetry and differential scanning calorimetry to identify endothermic transitions, infrared spectroscopy to monitor vibrational changes, X-ray or neutron diffraction to observe structural rearrangements, and high-resolution microscopy to visualize interfacial melting. As of now, issmelting remains a speculative term rather than a validated physical phenomenon.