Updating the Venus Atmospheric Structure for VIRA
Abstract
Many atmospheric profiles of the temperature structure have been obtained since the adoption of the Venus International Reference Atmosphere (VIRA) model in 1985 (Seiff et al., 1985) from occultations (Venus Express, Magellan and Akatsuki orbiters), passive remote sensing (VIRTIS on Venus Express) as well as balloons (VeGa 1 and VeGa 2) and descending probes through the atmosphere (VeGa 1 and VeGa 2 landers). Interim updates to the VIRA model were proposed by Moroz and Zasova (1997) and Zasova et al. (1996). Limaye et al. (2017) presented a comparison of post VIRA results on the atmospheric structure which included results from different Venus Express investigations as well as those from ground based observations. Akatsuki orbiter is currently obtaining radio occultation profiles of temperature (Imamura et al., 2017). These post VIRA data have expanded the coverage in latitude, longitude and local time and altitude, and thus updates to the temperature structure on Venus with altitude (pressure) and latitude and local time are possible and needed.It is worth re-visiting the thermal structure data in light of the apparent confirmation of a gradient in the nitrogen mixing ratio (Peplowski & Lawrence, 2016) as high as 64 km altitude from MESSENGER neutron spectrometer observations and was previously detected by (Oyama et al., 1980) but not explained. It is possible that this gradient exists because both the major constituents (carbon dioxide and nitrogen) of the Venus atmosphere should exist near the surface under supercritical conditions and the supercritical nature was not considered in any of the profiles. This density gradient can affect all calculations of altitude that involve the hydrostatic balance assumption and affect the adiabatic lapse rate (Lebonnois & Schubert, 2017).ReferencesImamura, T., Ando, H., Tellmann, S., Pätzold, M., Häusler, B., Yamazaki, A., et al. (2017). Initial performance of the radio occultation experiment in the Venus orbiter mission Akatsuki. Earth, Planets, and Space, 69. Lebonnois, S., & Schubert, G. (2017). The deep atmosphere of Venus and the possible role of density-driven separation of CO2 and N2. Nature Geosci, 10(7), 473-477. doi:10.1038/ngeo2971http://www.nature.com/ngeo/journal/v10/n7/abs/ngeo2971.html#supplementary-informationLimaye, S. S., Lebonnois, S., Mahieux, A., Pätzold, M., Bougher, S., Bruinsma, S., et al. (2017). The thermal structure of the Venus atmosphere: Intercomparison of Venus Express and ground based observations of vertical temperature and density profiles_. Icarus, 294, 124-155. doi:https://doi.org/10.1016/j.icarus.2017.04.020Moroz, V. I., & Zasova, L. V. (1997). VIRA-2: a review of inputs for updating the Venus International Reference Atmosphere. Advances in Space Research, 19, 1191-1201. Oyama, V. I., Carle, G. C., Woeller, F., Pollack, J. B., Reynolds, R. T., & Craig, R. A. (1980). Pioneer Venus gas chromatography of the lower atmosphere of Venus. Journal of Geophysical Research, 85, 7891-7902. Peplowski, P. N., & Lawrence, D. J. (2016). Nitrogen Content of Venus' Upper Atmosphere from the MESSENGER Neutron Spectrometer. Paper presented at the Lunar and Planetary Science Conference. http://adsabs.harvard.edu/abs/2016LPI....47.1177PZasova, L. V., Moroz, V. I., & Linkin, V. M. (1996). Venera-15, 16 and VEGA mission results as sources for improvements of the Venus reference atmosphere. Advances in Space Research, 17, 171-180.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E2017L