Determining Limits on the Intensity of the O2 0-0 Atmospheric Band Emission in the Venus Nightglow

Details Determining Limits on the Intensity of the O2 0-0 Atmospheric Band Emission in the Venus Nightglow Determining Limits on the Intensity of the O2 0-0 Atmospheric Band Emission in the Venus Nightglow

Dec 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p13a1664s&link_type=abstract

American Geophysical Union, Fall Meeting 2011, abstract #P13A-1664

Astronomy and Astrophysics

Astronomy

[0310] Atmospheric Composition And Structure / Airglow And Aurora, [6295] Planetary Sciences: Solar System Objects / Venus

Scientific paper

Recombination of oxygen atoms is the source of excited O2 states in the nighttime mesospheres of the terrestrial planets - Venus, Earth, and Mars. Emission in the O2 Atmospheric 0-0 band at 762 nm is one of the strongest features in the terrestrial visible/near-IR spectral region, with a typical intensity of 5 kR, although this emission does not reach the ground due to self-absorption. We inquire as to what intensity is expected at Venus, although there are no published spectra for either Venus or Mars in this spectral region. A recent estimated upper limit of 200 R for Venus has been given [Krasnopolsky, 2011]. The calculation requires knowledge of the temperature-dependent rate coefficients for three-body oxygen atom recombination in CO2 and for O2(b, v = 0) removal by CO2, as well as an estimate for the fraction of stabilized excited O2 molecules that reach b(v = 0). The resultant nadir intensity depends on [O(3P)]2, and for a value of [O(3P)] = 1.5 × 1011 cm-3, the 95-km intensity is of the order of 2 R, probably accurate to within a factor of two. Such a value is consistent with the lack of detection in recent Venus Express VIRTIS spectra, which include the 762 nm region. Measurements of the Venus nightglow with the 3.5-m telescope at Apache Point Observatory in December, 2010 also show no 762 nm emission, where in principle the 0.03 nm Doppler shift in the emission due to the relative velocities of Earth and Venus could have made observation possible. The principal differences between the Venus and Earth cases are (1) quenching of O2(b, v = 0) is more than two orders of magnitude faster by CO2 than by N2 (the terrestrial quencher) and (2) the densities in the ~95 km mesospheric nightglow region are two orders of magnitude higher at Venus. TGS acknowledge support for this work from the NASA Planetary Astronomy Program, Grant NNX08A0276. AM acknowledges ASI for support. Krasnopolsky, V.A., Planet. Space Sci. 59, 754-766, 2011.

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