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Tropospheric carbon monoxide concentrations and variability on Venus from Venus Express/VIRTIS-M observations

Tsang, Constantine C. C. and Irwin, Patrick G. J. and Wilson, Colin F. and Taylor, Fredric W. and Lee, Chris and de Kok, Remco and Drossart, Pierre and Piccioni, Giuseppe and Bezard, Bruno and Calcutt, Simon (2008) Tropospheric carbon monoxide concentrations and variability on Venus from Venus Express/VIRTIS-M observations. Journal of Geophysical Research E, 113 . Art. No. E00B08. ISSN 0148-0227. doi:10.1029/2008JE003089.

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We present nightside observations of tropospheric carbon monoxide in the southern hemisphere near the 35 km height level, the first from Venus Express/Visible and Infrared Thermal Imaging Spectrometer (VIRTIS)-M-IR. VIRTIS-M data from 2.18 to 2.50 μm, with a spectral resolution of 10 nm, were used in the analysis. Spectra were binned, with widths ranging from 5 to 30 spatial pixels, to increase the signal-to-noise ratio, while at the same time reducing the total number of retrievals required for complete spatial coverage. We calculate the mean abundance for carbon monoxide at the equator to be 23 ± 2 ppm. The CO concentration increases toward the poles, peaking at a latitude of approximately 60°S, with a mean value of 32 ± 2 ppm. This 40% equator-to-pole increase is consistent with the values found by Collard et al. (1993) from Galileo/NIMS observations. Observations suggest an overturning in this CO gradient past 60°S, declining to abundances seen in the midlatitudes. Zonal variability in this peak value has also been measured, varying on the order of 10% (~3 ppm) at different longitudes on a latitude circle. The zonal variability of the CO abundance has possible implications for the lifetime of CO and its dynamics in the troposphere. This work has definitively established a distribution of tropospheric CO, which is consistent with a Hadley cell circulation, and placed limits on the latitudinal extent of the cell.

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Additional Information:© 2008 American Geophysical Union. Received 26 January 2008; revised 10 June 2008; accepted 25 June 2008; published 1 October 2008. I would like to thank Emmanuel Marcq for his discussions of CO and his work with VIRTIS-H spectra and its findings. We would also like to thank Frank Mills and Robert Carlson for their discussions on this subject. This work was made possible from funding given by the United Kingdom Science Technology Facilities Council, as well as the continued support of CNES and ASI.
Funding AgencyGrant Number
United Kingdom Science Technology Facilities CouncilUNSPECIFIED
Centre National d'Etudes Spatiales (CNES)UNSPECIFIED
Astronomical Society of India (ASI)UNSPECIFIED
Subject Keywords:lower atmosphere; deep atmosphere; radiative-transfer; CO2; temperature; absorption; nightside; spectroscopy; scattering; retrieval
Record Number:CaltechAUTHORS:TSAjgre08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13387
Deposited By: Tony Diaz
Deposited On:04 May 2009 18:19
Last Modified:08 Nov 2021 22:37

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