Venus Photochemistry and Ground-based Observations
Abstract
There is relatively little detailed information on the nightglow photochemistry of Venus, and by implication, Mars. Two outstanding questions relate to the chemistry through which the CO2 atmospheres are stabilized, and to the mechanism for production of the O(1S) state, the green line source. We believe that it is possible that the two issues are related. The O2(c) state, in level v = 0, is a strong emitter in the Venus atmosphere, in the Herzberg II c-X bands, with an intensity of 3-5 kR. The O(1S) state, earlier believed to be absent in the Venus nightglow, is now known to have an intensity that can be at least as high as its terrestrial counterpart. Over the last few years, several ground-based green line observations have been carried out, and the intensity is found to be quite variable. Because of the substantial concentration of O2(c, v = 0) in the atmosphere, we have proposed that it may react with CO, simultaneously converting CO to CO2 and generating O(1S). Measurements have been made of the rate coefficients for removal of O2(c) by various colliders, including CO, all being fast. To date, only high vibrational level, v = 9-11, have been investigated. Subsequent work must concentrate on the v = 0 level. New ground-based nightglow observations have been carried out in spring, 2007, to measure the green line and the Herzberg II emission, as well as the O2 IR Atmospheric band at 1.27 microns, with further measurements being planned for the fall.There is relatively little detailed information on the nightglow photochemistry of Venus, and by implication, Mars. Two outstanding questions relate to the chemistry through which the CO2 atmospheres are stabilized, and to the mechanism for production of the O(1S) state, the green line source. We believe that it is possible that the two issues are related. The O2(c) state, in level v = 0, is a strong emitter in the Venus atmosphere, in the Herzberg II c-X bands, with an intensity of 3-5 kR. The O(1S) state, earlier believed to be absent in the Venus nightglow, is now known to have an intensity that can be at least as high as its terrestrial counterpart. Over the last few years, several ground-based green line observations have been carried out, and the intensity is found to be quite variable. Because of the substantial concentration of O2(c, v = 0) in the atmosphere, we have proposed that it may react with CO, simultaneously converting CO to CO2 and generating O(1S). Measurements have been made of the rate coefficients for removal of O2(c) by various colliders, including CO, all being fast. To date, only high vibrational level, v = 9-11, have been investigated. Subsequent work must concentrate on the v = 0 level. New ground-based nightglow observations have been carried out in spring, 2007, to measure the green line and the Herzberg II emission, as well as the O2 IR Atmospheric band at 1.27 microns, with further measurements being planned for the fall.
- Publication:
-
Planetary Atmospheres
- Pub Date:
- 2007
- Bibcode:
- 2007plat.work..109S