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T. G. Slanger (SRI), N.J. Chanover (NMSU), P.C. Cosby (SRI), D. Crisp (JPL), D.L. Huestis (SRI)
Dayside photodissociation of CO2 results in oxygen atoms and carbon monoxide molecules that are transported by winds to the nightside. A portion of this stored chemical energy appears as visible and infrared nightglow emissions. For example, the intensity of 1.27 micron emission from O2(a) roughly corresponds to the dayside photodissociation rate. That the visible wavelength emissions from O2(c) are much weaker is explained by more rapid quenching. Oxygen atom green-line emission is weaker yet, sometimes conspicuous and often imperceptible. The intensity of O2(a) is also observed to vary by 20% in an hour and by a factor of 10 across the nightside. The O2(c) emissions appear to be more stable, varying by about a factor of 2 between the four observations.
We will review recent telescope observations and suggest a new chemical reaction, O2(c) + CO arrow O(1S) + CO2 + 0.2 eV, that could be the source of the green-line emission, if the rate coefficient were as large as 10-13 cm3s-1. Variation in the local CO density could drive variability in the molecular oxygen nightglow if the rate coefficient for the other channels, O2(A,A',c) + CO arrow O(1D,3P) + CO2, were as large as 10-11 [O atom production is known to be that fast for collisions of O2(X) with high vibrational levels of O2(A)]. In that case, it would also become a significant player in the photochemical stability of the Venus atmosphere.
Supported by NSF and NASA Planetary Astronomy and Atmospheres programs.
The author(s) of this abstract have provided an email address for comments about the abstract: tom.slanger@sri.com
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.