NASA SPACE BIOLOGY AIMS TO UNDERSTAND ORGANISM ADAPTATIONS TO THE SPACEFLIGHT ENVIRONMENT. AN UNDERSTUDIED AREA OF SPACE BIOLOGY ARE THE SPACEFLIGHT ADAPTATIONS OF THE VENOUS CIRCULATION. THE VENOUS CIRCULATION SUPPORTS THE CARDIOVASCULAR SYSTEM, AND IN TURN ALL ORGANS OF THE BODY, BY TRANSPORTING BLOOD AND ITS CONTENTS AWAY FROM ORGAN SYSTEMS TOWARD THE HEART AND LUNGS. CONSEQUENTLY, VENOUS RETURN IMPACT'S CARDIAC FUNCTION. AS NASA AIMS TO SEND ASTRONAUTS TO THE MOON AND MARS, UNDERSTANDING THE ADAPTATIONS OF THE VENOUS CIRCULATION TO MICROGRAVITY, LUNAR GRAVITY, AND MARTIAN GRAVITY WILL NOT ONLY INCREASE OUR KNOWLEDGE OF CARDIOVASCULAR FUNCTION IN SPACE ALONG A GRAVITY CONTINUUM, BUT ALSO UNCOVER NEW POTENTIAL ASTRONAUT MEDICAL RISKS. FURTHERMORE, NASA WILL ALSO BE SENDING THE FIRST FEMALE ASTRONAUT INTO DEEP SPACE AS PART OF THE ARTEMIS MOON VENTURE, AND TO DATE THERE EXISTS NO LITERATURE ON POSSIBLE SEX DIFFERENCES OF THE VENOUS CIRCULATION IN RESPONSE TO SPACEFLIGHT. THIS STUDY WILL BE THE FIRST COMPREHENSIVE ASSESSMENT OF VENOUS CIRCULATION ADAPTATIONS TO A SIMULATED GRAVITY CONTINUUM AND ALSO INVESTIGATE SEX DIFFERENCES TO INCREASE OUR KNOWLEDGE OF MALE AND FEMALE CARDIOVASCULAR SPACE BIOLOGY ADAPTATIONS. I WILL INVESTIGATE, FOR THE FIRST TIME, THE FUNCTIONAL, STRUCTURAL, AND MOLECULAR ADAPTATIONS OF VEINS FROM MULTIPLE ORGAN BEDS (HEAD, HEART, DIGESTIVE SYSTEM, AND BONE) TO IDENTIFY VASCULAR BIOLOGY, IMMUNOLOGICAL, AND LOCAL ORGAN SYSTEM PHYSIOLOGICAL ADAPTATIONS TO SIMULATED SPACEFLIGHT ENVIRONMENT CONDITIONS. IN COMPLETING THIS STUDY, WE WILL HAVE INCREASED OUR OVERALL KNOWLEDGE AND UNDERSTANDING OF SPACE BIOLOGY, AS WELL AS IDENTIFY PROSPECTIVE HEALTH RISKS OF OUR ASTRONAUTS IN ADVANCE ON THEIR JOURNEY INTO DEEP SPACE.