HIGH PRESSURE PHASES IN H2O RICH PLANETARY BODIES

High-pressure phases of H₂O are of great importance in planetary physics. The NaCl-H₂O system serves as a good first order approximation of the impacts of impurities on the equation of state and melting curve of high-pressure phases of H₂O and can be used as analogues for more complicated planetary systems. Recent studies (Frank et al., 2006 and 2008, PEPI) have demonstrated that ice VII formed from a NaCl-bearing aqueous solution at pressures greater than 2.2 GPa and less than 500 K can be indexed by ice VII only, whereas at temperatures greater than 500 K, diffraction lines indicative of halite (NaCl) are observed and become more intense with increasing temperature and only disappear at the melting point of the high-pressure ice. Frank et al. (2008) noted this phenomenon was observed in all NaCl-bearing ice VII samples heated to greater than 500 K. Phase unmixing combined with the depression of the NaCl-doped ice VII melting curve could promote the formation of a self segregating layer or zone deep within ice-rich bodies. Thus, the exsolution of halite from the NaCl-doped ice VII at elevated temperatures may produce salt-rich diapirs that could generate salt-bearing aqueous vents and/or doming on H₂O-rich planetary bodies. Here, we will present various density profile models examining the implications of these properties. The models will allow for more precise and accurate density profile modeling of H₂O-rich bodies and provides an intriguing possible explanation for salt-rich surface features on select icy satellites.