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Non-LTE emission from VIRTIS/Venus Express observations

Non-LTE emission from VIRTIS/Venus Express observations. Pierre Drossart 1 With Giuseppe Piccioni 2 , Gabriella Gilli 3 , M. Lopez-Valverde 3 , Raphaël Garcia 4 and the VIRTIS/VEX team. 1 LESIA, Observatoire de Paris 2 IAPS, CNR, Rome; 3 IAA, Granada, 4 IRAP, Toulouse. Launch :

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Non-LTE emission from VIRTIS/Venus Express observations

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  1. Non-LTE emission from VIRTIS/Venus Express observations Pierre Drossart1 With Giuseppe Piccioni2, Gabriella Gilli3, M. Lopez-Valverde3, Raphaël Garcia4 and the VIRTIS/VEX team 1LESIA, Observatoire de Paris 2IAPS, CNR, Rome; 3IAA, Granada, 4 IRAP, Toulouse

  2. Launch : 9 November 2005 Orbit insertion: 11 April 2006 Today : ~2364 orbits

  3. VIRTIS for Venus Express – 7 years after… P. Drossart, G. Piccioni – in mem. A. Coradini Pierre Drossart Москва, ИКИ РАН3M-S3

  4. Aeronomy of Venus The upper atmosphere of planets exhibit a large variety of physical processes, essential to understand the interaction of a planet with its environment, but these regions are difficult to sound, and still relatively poorly explored! Pierre Drossart Москва, ИКИ РАН 3M-S3

  5. O2 average emission (L. Soret and JC. Gérard , Liège) O2 emission altitude : ~95 km Pierre Drossart Москва, ИКИ РАН 3M-S3

  6. VIRTIS O2 Herzberg II spectrum obs. Cf Migliorini et al – O2 emission altitude ~ 95 – 105 km Mean spectrum, obtained by averaging about 8700 spectra, acquired in the period 17-03-2010 – 28-02-2011. Identification of 8 Herzberg II bands. In addition, 3 Chamberlain bands are observed. Pierre Drossart Москва, ИКИ РАН 3M-S3

  7. OH and O2 emission on Venus OH altitude emission ~ 95 km as O2 cf Piccioni et al 2009 A.V. Shakun, PhD Thesis 2012 Pierre Drossart Москва, ИКИ РАН 3M-S3

  8. NO observations from VIRTISon VenusGarcia-Munoz et al, PNAS, 2009 NO altitude (from UV/SPICAV) : ~110 km Pierre Drossart Москва, ИКИ РАН 3M-S3

  9. Basics on non-LTE models for Venus, Mars and the Earth : 1) CO CO 4.7 µm levels scheme CO 4.7 µm Vibrational temperatures Gilli et al. 2011 LTE breakdown for CO(2) occurs at higher pressure then CO(1) in the 3 planets FB and FH bands: main bands responsible for the 4.7 µm emission Pierre Drossart Москва, ИКИ РАН 3M-S3

  10. Results from CO 4.7 m analysis (I) • Rotational lines identified according to the spectral resolution of the instruments Formisano et al. 2005 Formisano et al.2005 Mars 80-110km • In Mars and Venus, FH lines dominate the emission at 100 km, FB becomes optically thin in the upper layers • On the Earth the FB is optically thin at all altitudes, due to the smaller abundance of CO. Funke et al. 2007 Venus 100 km 150 km Earth 68 km Funke et al 2005 Gilli et a. 2011 Pierre Drossart Москва, ИКИ РАН 3M-S3

  11. Results from CO 4.7m analysis (I) • Emitted radiance proportional to the amount of emitters in opt. thin condition • FB, and FH lines saturated in the mesosphere of Venus and Mars (opt. thick condition) • FH and FB band do not saturate at any altitudes on the Earth Gilli et al. 2011 Pierre Drossart Москва, ИКИ РАН 3M-S3

  12. Results from CO 4.7 m analysis (II) (focus on Venus and Mars) 80-110 km 100 km 150 km Gilli et al. 2011 Data-model comparison for the first time at 4.7 m. Good overall agreement. In Mars the residuals are within the noise level The knowledge of the actual thermal structure on Venus and Mars is required Pierre Drossart Москва, ИКИ РАН 3M-S3

  13. Results: VIRTIS-H CO density (I) Difficult to find spatial and diurnal variation, due to the irregular distribution of the data Local time variations No significant variations with Local Time observed in this latitude box Pierre Drossart Москва, ИКИ РАН 3M-S3

  14. Basics on non-LTE models for Venus, Mars and the Earth : 2) CO2 CO2 4.3 m levels scheme • FB band: Transition from 001 level to the ground • FH, SH bands: arises from higher energy states CO2 high energy states directly excited during daytime by solar absorption. Pierre Drossart Москва, ИКИ РАН 3M-S3

  15. Comparative planetology: atmosphere of the terrestrial planets • SIMILARITIES • UV, soft X-rays absorption in the Thermosphere • IR absorption in the mesosphere • DIFFERENCES • Venus and Mars thermosphere colder than on the Earth • O, CO about 10 times more abundant on Venus and Mars • Stronger cooling in the upper regions of Mars and Venus by the CO2 15-m vibrational excited levels • CO2 vmr on the Earth is 1000 time smaller Limb data from VIRTIS/Vex, PFS/Mex (Formisano et al. 2005) and results from MIPAS/Envisat (Funke et al. 2007) were used. Non-LTE models for Venus (Roldan et al. 2000, López-Valverde et al. 2007), for Mars (Lopez-Puertas and Lopez Valverde 1994) and for the Earth (Lopez-Puertas et al. 2005) Pierre Drossart Москва, ИКИ РАН 3M-S3

  16. Basics on non-LTE models for Venus, Mars and the Earth CO2 4.3 m Vibrational temperatures • LTE departure at similar pressure levels for Mars and Venus, lower pressure on Earth • Vibrational temperatures constant at the top of the atmosphere Lopez-Valverde, Gilli,… PSS, 2011 Pierre Drossart Москва, ИКИ РАН 3M-S3

  17. VIRTIS observations for CO2 non-LTE Gilli et al, JGR 2009 Pierre Drossart Москва, ИКИ РАН 3M-S3

  18. CO2 4.3-m non-LTE measurements VIRTIS-M maps VIRTIS-M spectra & profiles Gilli et al. JGR, 2009 - CO2 emission peak around 110-120 km - Higher emission at lower SZA • good S/N up to 160 km • Change in the overall shape of the band with altitude • The altitude peak is maximum at the centre of the band (4.32 m) Pierre Drossart Москва, ИКИ РАН 3M-S3

  19. R. Garcia, 2011 Pierre Drossart Москва, ИКИ РАН 3M-S3

  20. Pierre Drossart Москва, ИКИ РАН 3M-S3

  21. Pierre Drossart Москва, ИКИ РАН 3M-S3

  22. Pierre Drossart Москва, ИКИ РАН 3M-S3

  23. Pierre Drossart Москва, ИКИ РАН 3M-S3

  24. Pierre Drossart Москва, ИКИ РАН 3M-S3

  25. Pierre Drossart Москва, ИКИ РАН 3M-S3

  26. Pierre Drossart Москва, ИКИ РАН 3M-S3

  27. Что дальше на Венере ? Venus as seen by Akatsuki on 6 December 2010 from 600 000 km (UV- 380 nm)

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