Supercooled solutions of sodium perchlorate in TIP4P/2005 water: The effect of martian solutes on thermodynamics and structure.

This article investigates the thermodynamic and structural behavior of aqueous sodium perchlorate (NaClO4) solutions in supercooled water using molecular dynamics simulations with the TIP4P/2005 water model. Two concentrations, 1.63 wt% and 15.4 wt%, were studied to assess how the liquid–liquid critical point (LLCP) and water's anomalous properties are affected by solute presence, motivated by the relevance to liquid water beneath the Martian soil. Results show that the LLCP persists in both solutions, shifting to slightly higher temperatures and notably lower pressures at higher concentration, with a corresponding shrinkage of the low-density liquid (LDL) region; structurally, water retains its characteristic high-density liquid (HDL) and LDL phases even at elevated solute levels, with ions preferentially solvated in the HDL phase. These findings support the hypothesis that water's anomalies remain significant in perchlorate solutions under Martian-like conditions, potentially influencing the stability of liquid water on Mars.