THE PIONEER VENUS ORBITER (PVO) DISCOVERED AN INTERESTING ASPECT OF THE SOLAR WIND INTERACTION AT VENUS: SOMETIMES THERE WAS A SUBSTANTIAL MAGNETIC FIELD EMBEDDED IN THE IONOSPHERE BELOW 200 KM. THESE MAGNETIC FIELDS WERE NOT OF PLANETARY ORIGIN BUT WERE INDUCED BY THE SOLAR WIND TO ENSURE THAT PRESSURE BALANCE WAS MAINTAINED ACROSS THE NEAR-SPACE ENVIRONMENT. THE INDUCED FIELDS WERE MOSTLY OBSERVED WHEN THE IONOSPHERIC THERMAL PRESSURE WAS UNABLE TO HOLD OFF THE SOLAR WIND BY ITSELF. THE STRUCTURE AND VARIABILITY OF THE INDUCED MAGNETIC FIELDS THEIR DEPENDENCE ON UPSTREAM SOLAR WIND CONDITIONS AND THEIR AFFECT ON IONOPAUSE THICKNESS WERE STUDIED IN DEPTH THANKS TO THE GREAT INSTRUMENT PAYLOAD ON PVO. BUT IT WOULD NOT BE UNTIL THREE DECADES LATER THAT A PVO-LIKE MISSION CALLED MAVEN (MARS ATMOSPHERE AND VOLATILE EVOLUTION) WOULD BE SENT TO MARS LEAVING MANY LINGERING QUESTIONS ABOUT INDUCED MAGNETIC FIELDS AT MARS AND HOW THEY COMPARE WITH THOSE AT VENUS. WE PROPOSE A LARGE-SCALE COMPARATIVE PLANETOLOGY STUDY TO INVESTIGATE INDUCED MAGNETIC FIELDS IN THE IONOSPHERE OF VENUS AND MARS USING PVO AND MAVEN DATA. OUR INVESTIGATION WILL ADDRESS THREE SCIENCE QUESTIONS: 1. UNDER WHAT CONDITIONS DOES THE IONOSPHERE HAVE ENOUGH THERMAL PRESSURE TO HOLD OFF THE SOLAR WIND BY ITSELF? 2. WHAT FACTORS CONTROL THE INDUCED MAGNETIC FIELDS? 3. HOW DOES IONOPAUSE STRUCTURE CHANGE WITH INDUCED MAGNETIC FIELDS? EACH QUESTION WILL BE ADDRESSED THROUGH A SERIES OF TASKS AIMED TOWARDS MARS AND MAVEN DATA ANALYSIS. THEN WE WILL COMPARE THE MARS RESULTS WITH VENUS USING PREVIOUSLY PUBLISHED PVO RESULTS AND NEW ANALYSES OF PVO DATA. OUR INVESTIGATION WILL ESTABLISH NEW SIMILARITIES AND DIFFERENCES IN HOW THE SOLAR WIND INTERACTION AFFECTS THE LOW-ALTITUDE PLASMA ENVIRONMENTS OF VENUS AND MARS AND SHOW HOW THE SOLAR WIND INTERACTION AT NONMAGNETIZED PLANETS IS ALTERED BY PLANET-SPECIFIC PROPERTIES SUCH AS THE MARTIAN CRUSTAL MAGNETISM. OUR INVESTIGATION IS WELL WITHIN THE SCOPE OF THE SSW PROGRAM BECAUSE IT INCLUDES COMPARATIVE PLANETOLOGY TASKS AND ANALYSIS OF PIONEER VENUS ORBITER DATA. IT IS ALSO RELEVANT TO THE GOALS OF THE SSW PROGRAM AS DETAILED IN SECTION 1 OF THE C.3 DOCUMENT WHICH STATES THAT THE SSW PROGRAM "...VALUES RESEARCH IN COMPARATIVE PLANETOLOGY " AND "...SEEKS TO ADDRESS THE PHYSICAL AND CHEMICAL PROCESSES THAT AFFECT...ATMOSPHERES EXOSPHERES AND MAGNETOSPHERES OF PLANETARY BODIES." OUR INVESTIGATION IS ALSO RELEVANT TO THE "PLASMA ENVIRONMENTS" TOPICS LISTED IN THE C.3 DOCUMENT WHICH SEEK TO UNDERSTAND "FUNDAMENTAL PLASMA PROCESSES" AND "PLASMA INTERACTIONS WITH STRUCTURES AND BODIES".