Numerical Simulation of the Hydrological and Geochemical Environment in
 the Martian Subsurface, 20-9313

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Principal Investigators
Scott L. Painter
Cynthia Dinwiddie

Inclusion Dates: 04/01/02 - Current

Background - Methods for simulating non-isothermal, multiphase flow and geochemical transport in unsaturated geological media have matured in recent years, and are now used in a range of advanced terrestrial applications. Similar computational tools have a range of potential applications in Mars research. They may be used, for example, to support data analysis, test hypotheses regarding the evolution and current state of subsurface hydrological systems, and understand the potential for undesirable perturbations during future drilling or sample collection activities. This project is developing a prototype for a new computer code MARSFLO, which will simulate the hydrological and geochemical environment of the Martian subsurface. Demonstration simulations using the prototype code are intended to support future NASA research proposals.

Approach - The prototype version of MARSFLO will be based on a power balance equation coupled with mass conservation equations for CO2 and for water in the vapor, liquid and ice phases. The general modeling strategy is to use equilibrium constraints to reduce the system to three highly non-linear coupled conservation equations, which are then solved using an integral-finite-difference method and fully implicit time stepping similar to the SwRI-developed MULTIFLOTM code. The required constitutive relationships are being developed from the theory of freezing terrestrial soils and modified for Martian conditions. Gaps in the existing theory for freezing soils are being identified for further research, as are research needs relating to geochemical processes in frozen soils.

Accomplishments - A detailed modeling approach based on existing theory of freezing soils and published curve fits to thermophysical properties of water and ice was finalized. A flexible and highly modular code design was completed. Generic data structures were implemented, and key numerical routines from the MULTIFLO code were adapted to an object-oriented format to facilitate re-use in MARSFLO.

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