MOTIVATION RECENT DISCOVERIES OF TERRESTRIAL PLANETS ORBITING IN THE HABITABLE ZONE OF NEARBY STARS HAVE ENERGIZED A NUMBER OF COMMUNITIES AND INCREASED THE URGENCY OF DISCUSSIONS OF THE CRITERIA FOR HABITABILITY ON TERRESTRIAL WORLDS. ONE POTENTIAL "SHOW-STOPPER" FOR HABITABILITY ESPECIALLY AROUND ACTIVE M DWARF STARS IS THE ABILITY OF PLANETS TO RETAIN AN ATMOSPHERE WHEN EXPOSED TO THE PHOTON AND PARTICLE RADIATION FROM THEIR HOST STAR. ATMOSPHERIC ESCAPE INVOLVES MANY DISTINCT PHYSICAL PROCESSES THAT PROVIDE ENERGY FOR ATMOSPHERIC PARTICLES TO ESCAPE THE GRAVITY OF THEIR PLANET. SEVERAL OF THESE PROCESSES INVOLVE THE REMOVAL OF CHARGED PARTICLES (IONS) FROM ATMOSPHERES AND MAY BE PARTICULARLY IMPORTANT FOR PLANETS THAT LACK A STRONG GLOBAL MAGNETIC FIELD. A NUMBER OF SOPHISTICATED GLOBAL PLASMA MODELS HAVE THEREFORE BEEN DEVELOPED TO STUDY ATMOSPHERIC ESCAPE FROM TERRESTRIAL WORLDS. THESE MODELS ARE NOW WELL-VALIDATED BY OBSERVATIONS FROM PLANETS SUCH AS MARS VENUS AND TITAN. BUT RESULTS FOR THE DIFFERENT PLANETS ARE RARELY INTERCOMPARED WHICH IS AN ESSENTIAL STEP FOR UNDERSTANDING HOW LOSS PROCESSES WORK INDEPENDENT OF THE PLANET. A PROMISING PATH TOWARD A DEEPER UNDERSTANDING IS TO USE SIMULATIONS THAT HAVE BEEN VALIDATED BY OBSERVATIONS AND THEN "PLAY WITH THE KNOBS". OBJECTIVES OUR STUDY WILL FOCUS ON HOW A PLANET'S PROPERTIES INFLUENCE THE LOSS OF ATMOSPHERIC PARTICLES. WE WILL FOCUS ON THE LOSS OF CHARGED PARTICLES FROM ATMOSPHERES USING MODELS TO ADDRESS FOUR QUESTIONS: 1. HOW DO ION ESCAPE RATES SCALE WITH A PLANET'S SIZE? 2. HOW DO ION ESCAPE RATES SCALE WITH A PLANET'S ATMOSPHERIC COMPOSITION? 3. HOW DO ION ESCAPE RATES SCALE WITH A PLANET'S MAGNETIC FIELD STRENGTH (IN THE WEAK FIELD LIMIT)? 4. HOW DO THE ASSUMPTIONS OF THE MODEL (FLUID VS. KINETIC) INFLUENCE SCALING LAWS FOR ESCAPE? METHODOLOGY OUR WORK WILL PROCEED THROUGH APPLICATION OF TWO WELL-VALIDATED GLOBAL PLASMA MODELS FOR THE INTERACTION OF THE SOLAR WIND WITH UNMAGNETIZED PLANETARY ATMOSPHERES. THE MODELS WILL BE RUN FOR IDENTICAL INPUT CONDITIONS CORRESPONDING BOTH TO OUR SUN AND TO A "REPRESENTATIVE" M DWARF STAR CONTROLLING FOR A SINGLE PLANETARY PROPERTY AT A TIME. THE THREE PLANETARY PROPERTIES THAT WILL BE INVESTIGATED ARE THE SIZE OF THE PLANET THE ATMOSPHERIC COMPOSITION AND THE PLANETARY MAGNETIC FIELD STRENGTH. WE WILL RUN THE MODELS FOR SEVERAL CHOICES OF EACH PARAMETER DERIVING QUANTITATIVE SCALING LAWS FOR ION LOSS RATES FOR EACH MODEL. OUR FOCUS FOR THIS RESEARCH IS ON ION ESCAPE ALONE THOUGH PROCESSES THAT REMOVE NEUTRAL PARTICLES ARE IMPORTANT AT SOME PLANETS. WHILE IT IS OUR LONG TERM GOAL TO CONSIDER BOTH NEUTRAL AND ION ESCAPE IN AN INTEGRATED MANNER IT WOULD BE OVERLY AMBITIOUS TO PROPOSE SUCH AN EFFORT HERE. SIMILARLY WE FOCUS OUR INVESTIGATION ON THE INFLUENCE OF PLANETARY PROPERTIES (RATHER THAN EXTERNAL CONDITIONS) ON ION ESCAPE SINCE THIS IS AN UNEXPLORED AREA IS TRACTABLE WITHIN THE PERIOD OF THE AWARD AND HAS THE POTENTIAL TO TELL US WHICH KINDS OF PLANETS ARE MOST LIKELY TO RETAIN ATMOSPHERES. RELEVANCE OUR PROPOSED WORK PROBES THE ABILITY OF TERRESTRIAL PLANETS TO RETAIN THEIR ATMOSPHERES WHEN SUBJECTED TO PHOTON AND PARTICLE RADIATION FROM THEIR STAR. THE WORK IS THEORETICAL AND FOCUSED ON THE PROPERTIES OF A PLANET AND ITS ATMOSPHERE THAT RESULT IN ATMOSPHERIC RETENTION. ATMOSPHERIC RETENTION IN TURN INFLUENCES THE SURFACE HABITABILITY OF A PLANET BY CONTROLLING THE SURFACE PRESSURE AND TEMPERATURE AND INFLUENCING WHETHER THESE QUANTITIES ARE APPROPRIATE FOR THE PRESENCE OF LIQUID WATER. THE RESEARCH OBJECTIVES ARE NOT FOCUSED ON THE FORMATION OF PLANETARY BODIES THE FORMATION OF ORGANIC MOLECULES ANALYSIS OF SPACECRAFT DATA OR THE EVOLUTION OF SOLAR SYSTEM PLANETS. WE BELIEVE THAT THE WORK IS RELEVANT TO THE OBJECTIVES OF THE HABITABLE WORLDS PROGRAM AND IS NOT MORE RELEVANT FOR ANY OTHER NASA PROGRAM.