GOALS AND OBJECTIVES PRIOR TO THE ONSET OF THE MAVEN (MARS ATMOSPHERE AND VOLATILE EVOLUTION) MISSION IN 2014 ONLY TWO MEASUREMENTS OF THE IONOSPHERIC COMPOSITION EXISTED. THEY CAME FROM THE VIKING 1 AND 2 LANDERS IN 1976. THIS IS WHY ONE OF THE THREE HIGH-LEVEL SCIENCE OBJECTIVES OF THE MAVEN IS TO MEASURE THE COMPOSITION AND STRUCTURE OF THE UPPER ATMOSPHERE AND IONOSPHERE TODAY AND DETERMINE THE PROCESSES RESPONSIBLE FOR CONTROLLING THEM (JAKOSKY ET AL. 2015). TO HELP MAVEN REACH SCIENCE CLOSURE ON THIS OBJECTIVE WE PROPOSE TO USE MEASUREMENTS FROM THE MAVEN NGIMS (NEUTRAL GAS AND ION MASS SPECTROMETER) INSTRUMENT. OUR INVESTIGATION CAN BE SUMMARIZED WITH A SINGLE SCIENCE QUESTION THAT WE WILL ADDRESS WITH FOUR TASKS: OVERARCHING SCIENCE QUESTION: HOW DOES THE CHEMICAL COMPOSITION OF THE IONOSPHERE VARY WITH SOLAR ZENITH ANGLE SEASON SOLAR ROTATION AND DUST? TASK 1: CREATE A DATABASE OF MEDIAN COMPOSITION PROFILES (20 ION SPECIES AND 5 NEUTRAL SPECIES) AND ARCHIVE THEM ON THE NASA PDS (PLANETARY DATA SYSTEM) SO THAT THE COMMUNITY CAN VALIDATE THEIR IONOSPHERIC MODELS PERFORM SCIENTIFIC INVESTIGATIONS OR USE THEM AS BOUNDARY CONDITIONS IN SIMULATIONS OF ESCAPE PROCESSES. TASK 2: SHOW HOW THE PEAK DENSITIES AND PEAK ALTITUDES OF EACH ION LAYER VARY WITH SOLAR ZENITH ANGLE AND SEASON AND DETERMINE WHICH PEAKS FORM AT A CONSTANT ATMOSPHERIC PRESSURE LEVEL. TASK 3: DETERMINE HOW THE CHEMICAL COMPOSITION OF THE IONOSPHERE RESPONDS TO CHANGES IN LOWER ATMOSPHERIC DUST LEVELS. TASK 4: SHOW HOW THE CHEMICAL COMPOSITION OF THE IONOSPHERE RESPONDS TO CHANGES IN THE SOLAR EUV FLUX ASSOCIATED WITH THE 27-DAY ROTATION PERIOD OF THE SUN. METHODOLOGY OUR INVESTIGATION WILL BE BASED ON THE PUBLICLY AVAILABLE NGIMS MEASUREMENTS OF NEUTRAL AND ION DENSITIES. IN TASK 1 WE WILL DERIVE MEDIAN COMPOSITION PROFILES BY COMPUTING ALTITUDE-AVERAGES OF NGIMS DATA FROM 30 CONSECUTIVE MAVEN ORBITS (TREATING INBOUND AND OUTBOUND DATA SEPARATELY). ONCE COMPLETE WE WILL HAVE CONSTRUCTED A DATABASE OF ION ALTITUDE PROFILES FOR 20 DIFFERENT ION SPECIES (HALF OF THESE LOCATIONS WILL ALSO HAVE CORRESPONDING NEUTRAL PROFILES). WE WILL ARCHIVE THE PROFILES ON THE ATMOSPHERES NODE OF NASA S PDS AND ANALYZE THEM IN TASK 2-4. IN TASK 2 WE WILL QUANTIFY HOW THE PEAK ALTITUDES AND PEAK DENSITIES OF THE DIFFERENT ION LAYERS VARY WITH SOLAR ZENITH ANGLE AND SEASON BY DERIVING BEST-FIT PARAMETERS TO EQUATIONS THAT DESCRIBE THE SZA VARIATIONS. IN TASK 3 WE WILL LOOK FOR UNUSUAL COMPOSITION CHANGES ASSOCIATED WITH THE ANNUAL DUST CYCLE ON MARS. THE DUST DATA WILL COME FROM COLLABORATOR LUCA MONTABONES HIGH LEVEL MAPS OF THE DUST IR OPTICAL DEPTH. IN TASK 4 WE WILL USE LEVEL 3 DATA FROM MAVEN S EUV MONITOR TO DETERMINE HOW EACH ION VARIES WITH THE SOLAR EUV FLUX AND HOW THE VARIATIONS DEPEND ON ALTITUDE. PERCEIVED IMPACT AND MDAP JUSTIFICATION AT THE CONCLUSION OF OUR INVESTIGATION WE WILL HAVE (1) CREATED AN ARCHIVED DATABASE OF MEDIAN COMPOSITION PROFILES THAT THE COMMUNITY CAN ANALYZE OR USE IN MODELING STUDIES; (2) SHOWN HOW THE PEAKS OF 14 DIFFERENT ION LAYERS VARY WITH SOLAR ZENITH ANGLE AND SEASON AND DETERMINED WHICH PEAKS FORM AT A CONSTANT ATMOSPHERIC PRESSURE LEVEL; (3) DETERMINED THE EXTENT IN WHICH THE ANNUAL MARTIAN DUST CYCLE AFFECTS THE ION COMPOSITION; AND (4) SHOWN HOW THE ION COMPOSITION CHANGES IN RESPONSE TO THE 27-DAY ROTATION PERIOD IN THE SOLAR EUV FLUX. WITH THESE RESULTS WE WILL HAVE ANSWERED OUR OVERARCHING SCIENCE QUESTION AND MADE SIGNIFICANT PROGRESS IN HELPING THE MAVEN MISSION REACH SCIENCE CLOSURE ON ONE OF ITS HIGHEST LEVEL OBJECTIVES. OUR INVESTIGATION THEN WILL NOT ONLY HAVE A SIGNIFICANT IMPACT ON MARS IONOSPHERIC SCIENCE BUT IS ALSO EXTREMELY RELEVANT TO THE GOALS AND SCOPE OF THE MDAP PROGRAM AS DETAILED IN SECTION 1 OF THE C.9 DOCUMENT.