WE PROPOSE TO QUANTITATIVELY EVALUATE ONE SPECIFIC MECHANISM FOR THE FORMATION OF LIQUID WATER ON PRESENT-DAY MARS THAT WE CONSIDER PARTICULARLY PROMISING: MELTING OF SEASONAL WATER FROST IN ALCOVES. IN AREAS WITHIN ALCOVES THAT ARE SEASONALLY SHADOWED WATER FROST WILLACCUMULATE AND WHEN THE SUN RISES AGAIN TEMPERATURE INCREASES RAPIDLY AND MAY MELT THE FROST. WE WILL USE HIRISE-STEREO DERIVED DIGITAL ELEVATION MODELS (DEMS) AND THREE-DIMENSIONAL MODELING OF SHADOWS SURFACE TEMPERATURE NEAR-SURFACE TEMPERATURES AND SUBLIMATION IN RSLALCOVES TO TEST THIS HYPOTHESIS. THE GOAL IS TO QUANTITATIVELY ASSESS THE FULL CYCLE OF FROSTACCUMULATION WARMING AND MELTING IN THESE LOCAL ENVIRONMENTS. THE INVESTIGATION WILL ANSWERTHE FOLLOWING PROFOUND QUESTION: CAN LIQUID WATER FORM BY MELTING OF SEASONAL FROST IN ALCOVES AT PRESENT-DAY MARS CONDITIONS? THE MODEL RESULTS WILL BE COMPARED TO A SUITE OF OBSERVATIONAL CONSTRAINTS. WE WILL TAKE THE MODEL SURFACE TEMPERATURE OUTPUT AND COMPARE IT TO 1) MEASURED RSL GROWTH/RETREAT TIMESCALES (AT WHAT TEMPERATURES ARE THE RSL CHANGING?) AND TO 2) FREEZING POINT DEPRESSIONCALCULATIONS FOR CHLORIDE PERCHLORATE AND SULFATE SOLUTIONS AND/OR BRINES. THE RESULTS OF THIS PROJECT WILL YIELD A MORE DETAILED PICTURE OF THE THERMAL STATE OF RSL AND AS A CONSEQUENCE WHAT FLUIDS THEY COULD BE COMPOSED OF. THIS WILL HELP ESTABLISH IF THEY ARE "SPECIAL REGIONS" OR ARE TOO SALTY TO SUPPORT LIFE AS WE KNOW IT (RUMMEL ET AL. 2014). THE PROPOSED RESEARCH FALLS WITHIN THE SCOPE OF THE HABITABLE WORLDS PROGRAM AS IT IDENTIFIES ANDCHARACTERIZES THE DISTRIBUTION OF POTENTIALLY HABITABLE ENVIRONMENTS ON MARS. THE "ASTROBIOLOGICAL POTENTIAL OF PAST OR PRESENT ENVIRONMENTS ON OR IN THE MARTIAN SURFACE ORSUBSURFACE" IS SPECIFICALLY MENTIONED IN THE PROGRAM CALL. ALTHOUGH PRIMARILY A SCIENCE DRIVEN INVESTIGATION THE PROJECT WILL ALSO GENERATE HIGHER-ORDER DATA PRODUCTS FROM NASA MISSIONS TO MARS (HIRISE DEMS) AND IT WILL LEAD TO FURTHER DEVELOPMENT AND DISSEMINATION OF SOFTWARE TOOLS.