WIDESPREAD DISTRIBUTION OF VALLEY NETWORKS (VNS) AND OTHER ASSOCIATED GEOLOGIC EVIDENCE GATHERED BY RECENT MISSIONS POINT TO AN EARLY WARM AND WET CLIMATE WITH AN ACTIVE HYDROLOGIC CYCLE. HOWEVER CLIMATE MODELS STRUGGLE TO PRODUCE THE WARM AND WET CONDITIONS BECAUSE OF LOW LUMINOSITY OF THE EARLY SUN. MANY DIFFERENT SCENARIOS HAVE BEEN OFFERED TO EXPLAIN THIS CONUNDRUM: EPISODIC WARM AND WET CONDITIONS CREATED BY PERIODIC VOLCANIC ACTIVITY OR IMPACT CRATERING GROUNDWATER SAPPING ASSOCIATED WITH MAGMA INTRUSION AND HYDROTHERMAL ACTIVITIES OR SHORT-LIVED EPISODES OF TOP-DOWN MELTING OF THICK COLD-BASED ICE ON THE EQUATORIAL HIGHLANDS. GLOBAL SCALE QUANTITATIVE MORPHOMETRIC ANALYSES OF VNS MAY HELP DETERMINE THE LIKELINESS OF THESE DIFFERENT SCENARIOS BUT SUCH ANALYSES ARE LIMITED. THE GOAL OF THIS PROJECT IS TO TEST WHICH CLIMATE SCENARIO IS MOST CONSISTENT WITH THE SPATIAL DISTRIBUTION OF VN GEOMORPHOLOGY ON A GLOBAL SCALE. SPECIFICALLY WE WILL USE SPATIAL STATISTICS TOOLS TO TEST A) IF THE EARLY MARTIAN CLIMATE WAS FAVORABLE FOR VN FORMATION B) IF THIS CLIMATE WAS CONTINUOUS FOR LONG PERIODS OF TIME OR EPISODIC IN NATURE C) IF THE PREVIOUSLY PROPOSED NON-FLUVIAL PROCESSES ARE VIABLE MECHANISMS TO CREATE THE OBSERVED SPATIAL PATTERN OF VN GEOMORPHOLOGY. IF THE EARLY CLIMATE WAS CONTINUOUSLY WARM AND WET (DRIVEN BY SOLAR RADIATION) THE RESULTING VN GEOMORPHOLOGY WOULD BE STATISTICALLY SIMILAR ACROSS THE GLOBE. IF THE CLIMATE WAS ONLY EPISODICALLY WARM AND WET (DRIVEN BY IMPACT OR OTHER LOCAL PROCESSES) THE RESULTING VN GEOMORPHOLOGY WOULD BE STATISTICALLY DIFFERENT BY REGIONS. METHOD: WE WILL EXTRACT QUANTITATIVE MORPHOMETRIC ATTRIBUTES INCLUDING HACK S LAW EXPONENT BASIN HYPSOMETRY BASIN CIRCULARITY AND VN INCISION DEPTH AND ANALYZE IF THEY VARY BY REGIONS AND HOW THEY ARE RELATED TO POTENTIAL CLIMATE SCENARIOS. SPECIFICALLY WE WILL USE A) THE STANDARD ANALYSIS OF VARIANCE (ANOVA) WITH WELCH CORRECTION FOR UNEQUAL VARIANCES TO TEST IF THESE GEOMORPHIC ATTRIBUTES ARE SIGNIFICANTLY DIFFERENT FROM REGION TO REGION ON A GLOBAL SCALE AND B) PEARSON S CORRELATION ANALYSIS AND C) THE NEW SPADE METHOD AND V-MEASURE TO QUANTIFY WHICH CLIMATE SCENARIO PREDICTED PRECIPITATION PATTERN IS SIGNIFICANTLY ASSOCIATED WITH THE SPATIAL DISTRIBUTION OF GEOMORPHIC ATTRIBUTES. HACK S LAW IS THE POWER LAW RELATIONSHIP BETWEEN CHANNEL LENGTH L AND DRAINAGE AREA A: L.A^N WHERE N IS THE EXPONENT WITH VALUES BETWEEN 0.5 AND 0.7 FOR FLUVIAL RIVERS ON EARTH. BASIN HYPSOMETRY DESCRIBES THE DISTRIBUTION OF MASS WITH ELEVATION AND IS RELATED TO EROSIONAL PROCESSES AND MATURITY OF THE BASIN. BASIN CIRCULARITY DESCRIBES THE ELONGATION OF A BASIN AT DIFFERENT ELEVATIONS AND SIGNIFIES THE STYLE OF FLUVIAL EROSION AND CLIMATIC CONDITIONS. THE SPATIAL DISTRIBUTION OF VN DEPTH CAN ALSO OFFER INSIGHTS INTO EROSIONAL PROCESSES. SIGNIFICANCE: THE PROPOSED PROJECT WILL PROVIDE A GLOBAL PERSPECTIVE OF THE SPATIAL DISTRIBUTION OF VN GEOMORPHOLOGY AND THUS NEW INSIGHTS INTO THE PROCESSES AND CLIMATIC CONDITIONS RESPONSIBLE FOR THE VN FORMATION. IT WILL OFFER NEW DETAILED CONSTRAINTS FOR CLIMATE MODELERS TO CONSIDER IN RECONCILING THE CLIMATE MODELS WITH GEOLOGIC AND GEOMORPHIC RECORDS. THE RESULTS WILL CONTRIBUTE TO RESOLVING THE ON-GOING DEBATE REGARDING EARLY MARS CLIMATE CONDITIONS. RELEVANCE: UNDERSTANDING THE CLIMATE OF EARLY MARS AND THE HISTORY OF HYDROLOGIC ACTIVITIES AND CURRENT WATER AVAILABILITY IS PARAMOUNT TO ASSESSING THE EXISTENCE OF LIFE ON MARS AND POTENTIAL FOR HUMAN HABITABILITY. THE PROPOSED RESEARCH WILL TEST THE DIFFERENT CLIMATIC SCENARIOS OF EARLY MARS AND THUS NOT ONLY ENHANCE THE SCIENTIFIC RETURN FROM MGS MO MRO AND ME MISSIONS BUT ALSO IMPROVE OUR UNDERSTANDING OF THE EARLY MARS CLIMATE WHICH CAN IN TURN GUIDE THE SELECTION OF FUTURE LANDING SITES. THE FINDINGS WILL ALSO OFFER ADDITIONAL CONSTRAINTS FOR EARLY CLIMATE MODELING AND HELP WITH OUR SEARCH FOR LIFE ON MARS AND FUTURE HUMAN EXPLORATION.