MOTIVATION: .A COMMON ISSUE WITH PLASMA MEASUREMENTS MADE BY A SINGLE SPACECRAFT IS THAT IT IS DIFFICULT TO DISTINGUISH TEMPORAL AND SPATIAL VARIABILITY. FOR EXAMPLE A DENSE PLASMA CLOUD BEING CARRIED PAST A SPACECRAFT LOOKS THE SAME IN OBSERVATIONS AS THE SPACECRAFT PASSING INTO A STATIONARY REGION OF HIGH PLASMA DENSITY. THIS ISSUE HAS PLAGUED STUDIES OF THE MARS PLASMA ENVIRONMENT FOR FIVE DECADES. IF TEMPORAL VARIABILITY COULD BE UNAMBIGUOUSLY IDENTIFIED IN INSTANCES LIKE THE ONE DESCRIBED ABOVE THEN THREE KEY ISSUES ABOUT THE MARS NEAR-SPACE ENVIRONMENT COULD BE ADDRESSED. FIRST WE DON T UNDERSTAND HOW LONG IT TAKES A CHANGE IN UPSTREAM CONDITIONS AT MARS TO PROPAGATE THROUGH THE SYSTEM. SECOND WE DON T KNOW HOW STABLE (ON TIMESCALES LESS THAN A TYPICAL SPACECRAFT ORBIT PERIOD) THE PLASMA CONDITIONS ARE AT LOW ALTITUDES. THIRD WE KNOW THAT IONS ARE ESCAPING FROM THE ATMOSPHERE IN A NON-STEADY FASHION BUT WE DON T KNOW HOW THIS BURSTY ESCAPE FITS INTO THE BIGGER PICTURE. THE HELIOPHYSICS COMMUNITY HAS OVER THE PAST TWO DECADES DECOUPLED TEMPORAL AND SPATIAL VARIABILITY IN EARTH S MAGNETOSPHERE THROUGH THE USE OF MULTI-POINT MEASUREMENTS WHERE TWO OR MORE SPACECRAFT MAKE SIMULTANEOUS OBSERVATIONS. CLUSTER THEMIS AND MMS FOR EXAMPLE ALL EMPLOY THE MULTI-POINT APPROACH. THOUGH NO DEDICATED MULTI-SPACECRAFT MISSIONS HAVE BEEN FLOWN AT MARS IT IS POSSIBLE TO EMPLOY THIS HIGHLY SUCCESSFUL APPROACH USING SIMULTANEOUS OBSERVATIONS RETURNED FROM EXISTING ORBITERS WITH ANALOGOUS INSTRUMENTS. .OBJECTIVES: .WE WILL EXAMINE THE TEMPORAL EVOLUTION OF PLASMA IN THE MARTIAN INDUCED MAGNETOSPHERE. OUR STUDY WILL FOCUS ON TIMESCALES OF SECONDS TO HOURS. WE WILL USE CHARGED PARTICLE AND MAGNETIC FIELD DATA FROM BOTH MAVEN AND MARS EXPRESS (MEX) TO ADDRESS THREE QUESTIONS: 1. WHAT IS THE RESPONSE TIME TO CHANGES IN UPSTREAM CONDITIONS NEAR MARS? 2. HOW DO PLASMA CONDITIONS VARY WITHIN A GIVEN REGION OF SPACE NEAR MARS? 3. HOW DO DISTRIBUTIONS OF ESCAPING IONS EVOLVE AS THEY FLOW AWAY FROM MARS? METHODOLOGY: .OUR WORK WILL PROCEED THROUGH ANALYSIS OF CHARGED PARTICLE AND MAGNETIC FIELD MEASUREMENTS FROM MAVEN AND MEX. RELEVANT INSTRUMENTS FOR IONS INCLUDE MAVEN STATIC AND SWIA AND THE MEX ASPERA-3 IMA SENSOR. FOR ELECTRONS WE WILL USE MAVEN SWEA AND THE MEX ASPERA-3 ELS SENSOR. MAGNETIC FIELD WILL COME FROM MAVEN MAG ALONE. FOR OBJECTIVE 1 WE WILL IDENTIFY DISTURBANCES IN THE PLASMA ENVIRONMENT UPSTREAM FROM MARS OBSERVED BY ONE SPACECRAFT AND NOTE THE TIME DELAY BEFORE THE DISTURBANCE IS RECORDED BY THE OTHER SPACECRAFT EMBEDDED IN THE MARTIAN MAGNETOSPHERE. BY IDENTIFYING MANY SUCH EVENTS WE CAN INFER THE TYPICAL TIME LAG FOR PROPAGATION OF DISTURBANCES THROUGH DIFFERENT PARTS OF THE MARTIAN SYSTEM. FOR OBJECTIVE 2 WE WILL IDENTIFY INSTANCES WHERE BOTH SPACECRAFT PASS THROUGH THE SAME VOLUME OF SPACE NEAR MARS WITH SOME TIME DELAY (E.G. MEX PASSES ABOVE THE DAWN EQUATORIAL TERMINATOR 15 MINUTES AFTER MAVEN DOES). THESE EVENTS WILL THEN BE EXAMINED TO DETERMINE CHANGES IN PLASMA PROPERTIES AT DIFFERENT LOCATIONS AND OVER DIFFERENT TIMESCALES. FOR OBJECTIVE 3 WE WILL IDENTIFY PERIODS WHEN BOTH SPACECRAFT ARE IN THE MARTIAN INDUCED MAGNETO-TAIL. WE WILL THEN EXAMINE THE EVOLUTION OF NON-STEADY ESCAPING ION FLUXES WITH DOWNSTREAM DISTANCE FROM MARS. .RELEVANCE:. OUR PROPOSED WORK SEEKS TO ENHANCE THE SCIENTIFIC RETURN FROM BOTH MAVEN AND MEX. THE PRIMARY THRUST OF THE WORK IS OBSERVATIONAL (I.E. NOT FOCUSED ON MODELING OR THEORY) AND WILL USE ONLY DATA THAT ARE PUBLICLY AVAILABLE. THE RESEARCH OBJECTIVES ARE NOT CURRENTLY WITHIN THE SCOPE OF EITHER SPACECRAFT MISSION TEAM SINCE THE OBJECTIVES CAN ONLY BE ACCOMPLISHED BY USING DATA FROM BOTH MISSIONS TOGETHER. WE BELIEVE THAT THE WORK IS RELEVANT TO THE OBJECTIVES OF THE MARS DATA ANALYSIS PROGRAM AND IS NOT MORE RELEVANT FOR ANY OTHER NASA PROGRAM. .