Mass spectrometric measurements of the neutral gas composition of the thermosphere and exosphere of Venus

摘要: The neutral gas composition and density in the thermosphere of Venus is being measured with a quadrupole mass spectrometer on Pioneer orbiter. Data are obtained near periapsis once per day approximately 150-250 km above surface. principal gases CO2, CO, N2, O, N, He. Atomic oxygen major constituent 155 dayside also nightside up to 180 when helium becomes constituent. average values N remain nearly constant during night, but an abrupt change occurs across terminator from high value low value. varies opposite way, distinct bulge was observed at night morning terminator. data have been used as basis empirical model. Large orbit variations densities were nightside, suggesting perhaps strong turbulent motion atmosphere below. Kinetic temperatures inferred scale heights 285 K 110 night. global temperature model 199 K.