Molecular spectroscopy for planetary and exoplanetary radiative transfer : The rock of Sisyphus or the barrel of the Danaids? Pierre Drossart LESIA, Observatoire de Meudon
Situation of molecular spectroscopy for planetary atmospheres Giant planets main IR absorbers : CH 4, NH 3 minor absorbers : PH 3, CO, H2O, etc. Titan main IR absorber : CH 4 Telluric Planets (Venus, Earth, Mars) main IR absorber : CO 2 minor absorbers : H 2 O, CO, etc. 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 2
RT in the infrared : vibration-rotation of Vibration rotation bands of CO 2 in the infrared molecules : 1) CO 2 Lopez-Puertas & Taylor, 2001 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 3
vibration/rotation bands: 2) CH 4 7.8 µm 3.3 µm 2.3 µm 1.8 µm Dyad 2 vibrational states 2 sublevels Pentad 5 vibrational states 9 sublevels Octad 8 vibrational states 20 sublevels Tetradecad 14 vibrational states 60 sublevels Wenger and Champion, JQSRT, 1998 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 4
Earth transmittance Neglecting scattering e ν = k ν =>No angular dependence in the extinction coefficient (nor in the source function) All the complexity is in the absorption coefficients = molecular spectroscopy CO CH 4 N 2 O CO 2 H 2 O O 3 Lopez-Puertas & Taylor, 2001 all 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 5
Radiative transfer non-lte scheme Non-LTE regime: Jν Bν Thermal collision time > radiative time Collisional, chemical processes to be taken into account to calculate the source function Lopez-Puertas & Taylor, 2001 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 6
Non-thermal processes 1. Vibrational-vibrational energy transfer. Example : CO 2 molecule ; exchange with N 2 2. Electronic to vibrational energy transfer. Example: O( 1 D) state excitating the N 2 vibrational modes 3. Chemical recombination or chemiluminescence Example: ozone bands at 10 µm 4. Photochemical reactions Example : O 2 emissions at 1.27 µm 5. Dissociative recombination (O + 2 + e- O* + O) 6. Collisions with charged particles (auroral processes) 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 7
Telluric planets Near infrared spectra Non-LTE effects 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 8
The infrared spectrum of Martian atmosphere Solar reflected Thermal CO 2 H 2 O Hydrated CO 2 silicates CO 2 CO CO 2 Reflected sunlight -> mineralogy Thermal emission -> T(z), winds ISO-SWS Lellouch et al., 2000 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 9
Venus nightside windows 2.3 µm CFHT/FTS observations (Res = 0.15 cm -1 ) [Taylor et al. 1997] Altitude range: 26-45 km Absorbers: CO 2, H 2 O, HDO, CO, OCS, SO 2, HF CO 2 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 10
Venus night side spectra Venus Express / VIRTIS Obs. 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 11
Comparative planetology: atmosphere of the terrestrial planets Gabriella Gilli, IAA, PhD Thesis 2012 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 CO 2 15-µm vibrational excited levels CO 2 vmr on the Earth is 1000 time smaller 1. Limb data from VIRTIS/Vex, PFS/Mex (Formisano et al. 2005) and results from MIPAS/Envisat (Funke et al. 2007) were used. 2. 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) 11th ASA/12th HITRAN Conference - REIMS 30/08/2012 12
Basics on non-lte models for Venus, Mars and the Earth CO 2 4.3 µm levels scheme FB band: Transition from 001 level to the ground FH, SH bands: arises from higher energy states CO 2 high energy states directly excited during daytime by solar absorption. Gabriella Gilli, IAA, PhD Thesis 2012 11th ASA/12th HITRAN Conference - REIMS 30/08/2012 13
Results from CO 2 4.3 µm analysis Altitude variations Similar behaviour in the three planets Variation of the shape of the emission Maximum of the emission at 50 km, 110 km, 100 km on Earth, Venus and Mars. - SH bands - pressure level 1000 times denser on the Earth Gabriella Gilli, IAA, PhD Thesis 2012 30/08/2012 Lopez-Valverde, Gilli, PSS, 2011 11th ASA/12th HITRAN Conference - REIMS 14
VIRTIS observations for CO 2 non-lte Gilli et al, JGR 2009 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 15
Basics on non-lte models for Venus, Mars and the Earth CO 4.7 µm levels scheme CO 4.7 µm Vibrational temperatures Gilli et al. 2011 FB and FH bands: main bands responsible for the 4.7 µm emission LTE breakdown for CO(2) occurs at higher pressure then CO(1) in the 3 planets Gabriella Gilli, IAA, PhD Thesis 2012 11th ASA/12th HITRAN Conference - REIMS 30/08/2012 16
VIRTIS-H 4.7 µm individual spectra - Individual spectra observed up to 120 km -FH and FB rotational lines identified - FH dominates the CO spectra in the lower mesosphere - VIRTIS-H promising to derive atmospheric parameters Gabriella Gilli, IAA, PhD Thesis 2012 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 17
OH and O 2 emission on Venus A.V. Shakun, PhD Thesis 2012 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 18
Titan Cassini/VIMS Titan observations @ T0 CM_1467449778.cub (#18) Spectrum in central regions 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 19
VIMS DISR comparison 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 20
Jupiter & Saturn Near IR spectra Non-LTE CH 4 spectra 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 21
Water at 5 µm as seen by NIMS-Galileo Roos-Serote et al, 1999 Map of an IR hot spot on Jupiter (Galileo Visible camera) 5-µm thermal emission (Galileo/NIMS) Variations of water vapor within the hot spot 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 22
Simplified scheme of fluorescence in CH 4 in Jupiter grouping stretching/ bending levels of CH 4 CH 4 radiative transitions: ν 3 (3.3µm) ν 4 (7.8µm) 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 23
CH 4 fluorescence in Jupiter atmosphere with ISO/SWS Objective with JIRAM: Mapping of the homopause level and CH 4 distribution above the homopause 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 24
Cassini/VIMS CH 4 emissions at 3.3 µm Jupiter (2000) Saturn (2005) 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 25
Cassini/VIMS Titan observations : resolution 130 km /phase angle 90 Circle = surface of Titan Profiles taken along the segments Limb profiles Peak emission at ~400km 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 26
Model (left) and Observed VIMS/T0 rebinned spectra (right) across Titan limb Altitude of the limb spectra raise from blue (1000km) to red (100 km). Shift of the peak from 3.31 to 3.33 at low altitudes <=> fundamental at high altitude / overtone at low altitude 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 27
Exoplanets See G. Tinetti presentation Molecules of interest : CH 4, CO 2, H 2 O, CO, etc. Main difference with planetary atmospheres : hot temperatures => many hot bands 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 28
Needs for atmospheric modeling Spectroscopy at short wavelengths for major constituents : CO 2, CH 4 Hot temperatures => hot band spectroscopy for exoplanets Minor constituents : H 2 O 2, OH, H 2 CO for telluric planets NH 3, PH 3, H 2 S for giant planets Hydrocarbons and nitriles for Titan Line broadening (H 2 for giant planets) Coefficients for relaxation line mixing Collision induced absorption 30/08/2012 11th ASA/12th HITRAN Conference - REIMS 29