Discovery of a Doppler-limited CO Line in the Upper Mesosphere of Venus: A New Dynamical Probe
Abstract
The presence of CO in the upper atmosphere of Venus is a consequence of the photochemistry of CO2, the dominant atmospheric constituent. In December 1989 the J = 1-2 transition of CO was observed at 230 GHz. In addition to the broad absorption line first reported by Kakar et al. (1976), a narrow absorption feature at the center of the line due to upper mesospheric CO, where the temperature profile starts to exhibit diurnal variation with altitude. The narrow feature is approximately 600 kHz wide and is predominantly Doppler-broadened. The Doppler core provides a new means of measuring wind velocities at these altitudes in the atmosphere of Venus. Detection of small Doppler shifts in the line core can in principle be used to measure winds with an accuracy of 10 m/s. Results are presently limited by the 17 kHz uncertainty in the measured rest frequency, corresponding to a systematic error in wind velocity up to 22 m/s, and the absence of laboratory measurements of the pressure shift in CO by CO2.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1991
- DOI:
- 10.1086/185949
- Bibcode:
- 1991ApJ...369L..17B
- Keywords:
-
- Carbon Monoxide;
- Doppler Effect;
- Mesosphere;
- Photochemical Reactions;
- Venus Atmosphere;
- Atmospheric Chemistry;
- Atmospheric Composition;
- Carbon Dioxide;
- Solar Radiation;
- VENUS;
- CARBON MONOXIDE;
- ATMOSPHERE;
- MESOSPHERE;
- PHOTOCHEMISTRY;
- WIND;
- ABSORPTION;
- VELOCITY;
- ALTITUDE;
- DOPPLER METHODS;
- SPECTRA;
- DYNAMICS;
- EARTH-BASED OBSERVATIONS;
- DIURNAL VARIATION;
- CIRCULATION;
- DISTRIBUTION;
- MODELS;
- ASTRONOMY;
- TEMPERATURE;
- SPACECRAFT OBSERVATIONS;
- PVO MISSION;
- Lunar and Planetary Exploration; Venus;
- PLANETS: SPECTRA;
- PLANETS: VENUS