Carbon monoxide emissions at from Venus’ atmosphere

Abstract: In January 1987, high-resolution spectra of the dayside of Venus in the 2080– range, recorded with the Canada–France–Hawaii telescope using a Fourier-transform spectrometer, revealed two sequences of narrow emission lines, corresponding to the and ) vibrational bands of carbon monoxide. Higher-quality spectra of Venus were recorded subsequently (September 1994) on several points on Venus. We present here the Venus observations and the associated intensities and rotational temperatures. Possible mechanisms responsible for these emissions are reviewed. We show that (1) fluorescence following infrared solar excitation and (2) photolysis leading to the creation of vibrationally excited CO are two plausible mechanisms. A quantitative model which takes into account these two processes, collisions and radiative trapping is presented and allows an approximate matching of the observed line intensities. Inferred temperatures are 170–220K for the (2–1) band, probing the 100–110km range, and 220–300K for the (1–0) band (125–145km altitude). [Copyright &y& Elsevier]