REMNANT GLACIAL LANDFORMS ON MARS INCLUDING LOBATE DEBRIS APRONS (LDA) LINEATED VALLEY FILL (LVF) AND CONCENTRIC CRATER FILL (CCF) ARE WIDESPREAD IN MID-LATITUDES AND TOGETHER CONSTITUTE AN AMAZONIAN-AGED DEBRIS-COVERED WATER ICE RESERVOIR EQUAL TO A GLOBAL EQUIVALENT WATER LAYER ~2 M THICK. ON THE BASIS OF CRATER RETENTION AGES AND BUFFERED CRATER COUNTING MEASUREMENTS GLACIAL LANDFORMS ON MARS WERE ACTIVE IN THE AMAZONIAN (~100-1000 MA). HOWEVER ON THE BASIS OF CRATER COUNTING ALONE IT IS IMPOSSIBLE TO DETERMINE WHETHER DEPOSITION OF THESE MAJOR MARTIAN ICE DEPOSITS OCCURRED EPISODICALLY DURING A FEW SHORT INSTANCES DURING THAT TIME PERIOD OR WHETHER GLACIATION WAS LARGELY CONTINUOUS THROUGHOUT THE PERIOD OF GLACIER GROWTH. THIS UNCERTAINTY DIRECTLY LIMITS OUR ABILITY TO USE THE GEOLOGIC RECORD TO DETERMINE THE INTENSITY OF ICE ACCUMULATION EVENTS ON MARS DURING THE AMAZONIAN AND THUS DETERMINE WHEN WHERE AND TO WHAT EXTENT WATER HAS BEEN ACTIVELY CIRCULATING THROUGH THE MARTIAN HYDROSPHERE AND CRYOSPHERE IN THE RECENT PAST. ACCORDINGLY THE OBJECTIVES OF THIS PROPOSAL ARE TO (1) MAKE NOVEL MEASUREMENTS OF BOULDER SIZE DISTRIBUTION ON THE DEBRIS LAYER OVERLYING LDA (2) TO USE THESE MEASUREMENTS TO ASSESS WHETHER GLACIAL EMPLACEMENT ON MARS WAS CONTINUOUS EPISODIC OR SPORADIC DURING THE LAST ~1 GY (3) ASSESS WHETHER GEOGRAPHICAL DIFFERENCES IN BOULDER TRANSPORT ICE ACCUMULATION OR GLACIAL STYLE ARE OBSERVED AND (4) DETERMINE IF FLOW EPISODICITY IMPLIED BY BOULDER SIZE DISTRIBUTIONS CAN BE REPRODUCED BY FLOW MODELING. METHODOLOGY. TO ADDRESS THIS GOAL WE PROPOSE TO USE HIRISE IMAGE DATA TO MEASURE THE BOULDER SIZE-FREQUENCY DISTRIBUTION ALONG LOBATE DEBRIS APRON FLOW PATHS IN THE NORTHERN AND SOUTHERN HEMISPHERES OF MARS IN ORDER TO DETERMINE WHETHER BOULDERS ARE FINER DOWN-FLOW (IMPLYING LONG-LIVED AND CONTINUOUS DEPOSITION) WHETHER DISTINCT POPULATIONS OF INCREASINGLY SMALLER BOULDERS ARE PRESENT ALONG THE FLOW DIRECTION (IMPLYING LONG-LIVED AND EPISODIC FLOW) OR WHETHER BOULDER POPULATIONS ARE UNIFORM IN SIZE ALONG THE FLOW DIRECTION (IMPLYING SHORT-LIVED FLOW). FLOW PATHS WILL BE DETERMINED THROUGH EXAMINATION OF CTX AND THEMIS-VIS DATA (TO IDENTIFY FLOWRELATED LINEATIONS) AND THROUGH CALCULATION OF MAXIMUM SLOPE PROFILES FROM MOLA AS WELL AS CTX AND HIRISE STEREO DEMS. FLOW MODELING WILL USE EXISTING LDA FLOW MODELS COUPLED TO SHARAD OBSERVATIONS OF BED SLOPE AND MODIFIED TO INCLUDE VARIABLE ACCUMULATION RATE. RELEVANCE. THE PROPOSED RESEARCH WILL USE MRO AND MGS DATA TO DIRECTLY IMPROVE OUR UNDERSTANDING OF THE ORIGIN CLIMATIC SIGNIFICANCE AND ISRU POTENTIAL OF ICE-RICH DEPOSITS IN THE MARTIAN MID-LATITUDES. THIS WORK WILL TRANSFORM OUR UNDERSTANDING OF LDA FROM SIMPLY CHARACTERIZING ITS SURFACE ATTRIBUTES TO UNDERSTANDING ITS RATE OF EMPLACEMENT AND ROLE IN MARTIAN CLIMATE. THIS HAS BEEN IDENTIFIED AS A MEPAG RESEARCH PRIORITY (GOAL 2 OBJECTIVE B INVESTIGATION 3). THUS THE PROPOSED RESEARCH IS A SCIENTIFIC INVESTIGATION BASED ON ANALYSIS OF PDS-ARCHIVED DATA FROM TWO NASA MISSIONS EXPLICITLY LISTED IN THE MDAP PROGRAM DESCRIPTION; THEREFORE THE PROJECT IS DIRECTLY RELEVANT TO MDAP.