JAROSITE SERVES AS AN INDICATOR MINERAL FOR SALTY AND LOW PH ENVIRONMENTS AND ITS DISSOLUTION PRODUCTS PROVIDE A RECORD OF TEMPERATURE PH AND LONGEVITY OF LIQUID WATER ON THE SURFACE OF MARS. JAROSITE AND ITS AL FORM ALUNITE ARE HYDROXYL-SULFATE MINERALS AND CAN BE DETECTED IN THE VISIBLE/NEAR-INFRARED CRISM IMAGES OF MARS THROUGH MULTIPLE SPECTRAL ABSORPTION BANDS. WE PROPOSE TO INVESTIGATE THE OCCURRENCE OF JAROSITE AND ALUNITE OUTCROPS IN SEVERAL LOCATIONS ACROSS MARS IN ORDER TO DETERMINE THE ENVIRONMENTS SUPPORTING THEIR FORMATION ON EARLY MARS AND THEIR PRESERVATION SINCE THEN. JAROSITE AND ALUNITE HAVE BEEN DETECTED FROM ORBIT AT MARS THROUGH ANALYSES OF CRISM IMAGES AT MULTIPLE SITES (E.G. FARRAND ET AL. 2010; WRAY ET AL. 2011 WEITZ ET AL. 2011; THOLLOT ET AL. 2012; EHLMANN ET AL. 2016). SURFACE ANALYSES AT GUSEV CRATER MERIDIANI PLANUM AND GALE CRATER HAVE ALSO SHOWN THE PRESENCE OF JAROSITE (E.G. KLINGELH FER ET AL. 2004; MORRIS ET AL. 2008; BRISTOW ET AL. 2018). OUR PROJECT INCLUDES A PURIFICATION STEP FOR THE CRISM IMAGES BECAUSE THE ORBITAL DETECTIONS OF JAROSITE AND ALUNITE ARE VERY SMALL AND SPECTRA WITH REDUCED NOISE ARE NECESSARY TO PRECISELY DESCRIBE THESE FEATURES. FURTHER WE ARE UTILIZING A NOVEL FEATURE EXTRACTION ALGORITHM TO FACILITATE IDENTIFICATION OF ALL OUTCROPS OF JAROSITE AND ALUNITE AT THE STUDY SITES AND ALSO TO CHARACTERIZE THE ASSOCIATED MINERAL ASSEMBLAGES. WE WILL EVALUATE THE MINERALOGY IN DETAIL FOR THE JAROSITE- AND ALUNITE-BEARING OUTCROPS AT SEVERAL LOCATIONS INCLUDING GALE CRATER COLUMBUS CRATER MAWRTH VALLIS NOCTIS LABYRINTHUS VALLES MARINERIS (AND NEARBY CHASMA) CROSS CRATER JEZERO CRATER AND NE SYRTIS. WE WILL DESCRIBE THE MORPHOLOGY OF THESE UNITS IN HIRISE IMAGERY AND CHARACTERIZE THEIR STRATIGRAPHY USING 3D CRISM/MOLA CRISM/HRSC AND CRISM/HIRISE SCENES. WE WILL ALSO APPLY THE RESULTS OF JAROSITE/ALUNITE STUDIES FROM LAB EXPERIMENTS GEOCHEMICAL MODELING FIELD SITES AND ROVERS DETECTIONS TO MORE FULLY UNDERSTAND THE ORBITAL IDENTIFICATIONS. UNDERSTANDING WHETHER THESE JAROSITE AND ALUNITE OUTCROPS FORMED IN HIGH TEMPERATURE VOLCANIC STEAM ENVIRONMENTS THROUGH ACID FOG DEPOSITION THROUGH ACID ICE REACTIONS IN ACIDIC BRINES FOLLOWING DISSOLUTION OF SULFIDES OR IN SALTY EVAPORATE POOLS WOULD INDICATE GREATLY DIFFERENT GEOCHEMICAL CONDITIONS. BURNS (1988) SUGGESTED THE PRESENCE OF GOSSANS ON MARS AND DEFINED THESE AS ALTERATION ASSEMBLAGES INCLUDING JAROSITE HYDRATED FERRIC OXIDES SILICA AND CLAYS. HE EMPHASIZED THE IMPORTANCE OF THESE MATERIALS FOR UNDERSTANDING MARTIAN GEOCHEMISTRY BY PARAPHRASING JENSEN AND BATEMAN (1979) GOSSANS ARE SIGNPOSTS THAT POINT TO WHAT LIES BENEATH THE SURFACE. THEY ARREST ATTENTION AND INCITE INTEREST AS TO WHAT THEY MAY MASK. THE FINDING OF ONE MAY HERALD THE DISCOVERY OF BURIED WEALTH. ALTERATION OF IGNEOUS SILICATES AND IRON SULFIDES ON MARS THROUGH ACIDIC GROUNDWATER WAS PROPOSED BY BURNS AND COLLEAGUES THROUGH SEVERAL STUDIES TO YIELD JAROSITE ALUNITE AND OTHER MINERALS. ELWOOD MADDEN AND COLLEAGUES HAVE EXTENDED THIS EARLY WORK BY BURNS THROUGH MODELING THE FORMATION CONDITIONS SUPPORTING FORMATION AND DISSOLUTION OF JAROSITE GROUP MINERALS. THESE STUDIES RESULTED IN FORMATION OF JAROSITE TOGETHER WITH IRON OXIDES/HYDROXIDES AND CLAYS ON MARS AS PREDICTED BY BURNS BUT EXPRESS THIS PROCESS USING JAROSITE AS AN INDICATOR MINERAL FOR THE DEGREE OF ALTERATION AND FOR THE EXTENT OF LIQUID WATER AVAILABILITY ON MARS. EXPERIMENTS AND MODELING INDICATE THAT JAROSITE/ ALUNITE WOULD NOT PERSIST LONG TERM ON THE MARTIAN SURFACE IN A LIQUID WATER/BRINE SETTING. THIS COULD EXPLAIN WHY THE OUTCROPS OF JAROSITE AND ALUNITE OBSERVED FROM ORBIT ON MARS ARE RELATIVELY SMALL COMPARED WITH OTHER AQUEOUS OUTCROPS AND WHY THEY OCCUR MIXED WITH IRON OXIDES/HYDROXIDES AND CLAYS. CHARACTERIZING THESE JAROSITE AND ALUNITE MINERAL ASSEMBLAGES WILL LEAD TO INFORMATION ABOUT THE AQUEOUS GEOCHEMISTRY CLIMATE AND HABITABILITY ON MARS.