Seasonal variation of structure of Martian atmosphere from LWC PFS data

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Clare Andrea Wheeler
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1 Seasonal variation of structure of Martian atmosphere from LWC PFS data Zasova L.V. (1,2), Grassi D. (2), Ignatiev N.I. (1,2), Formisano V. (2), M. Giuranna (2), Khatuntsev I.V. (1), Maturilli A. (2) and the PFS Team IKI, RAS, Moscow, Russia IFSI, INAF, Rome, Italy

2 Longwavelength channel of PFS covers a spectral range cm-1 1 with spectral resolution 1.8 cm-1 1 and allows to retrieve vertical temperature profiles from the surface up to km Vertical temperature profiles and aerosol opacity of Martian atmosphere may be retrieved from the same single spectrum on the day side, when the surface temperature is rather high. At night side the temperature is low and spectra have to be averaged. In the polar regions we also deal with spectra averaged over 2-10, so effective field of view increases up to km respectively.

4 1. Late winter. Orbits 20 and 68 O68,Ls=342 Tharsis Ascraeus Mons Alba Patera Polar hood CO2 polar cap Temperature field in coordinates latitude-altitude altitude along unique orbit 68 passed through the Northern polar region at night. Polar hood terminator Not known before: Temperature inversion in the N interval near 10 km altitude with temperature maximum at 20km altitude is found by PFS LWC measurements. Amplitude of thermal inversion reaches of 20K in the polar hood. It smooths out above the CO2 polar cap, where temperature maximum corresponds to the altitudes not available for the observations with spectral resolution of PFS (polar warming). -Thermal inversion is a results of dynamics (in descending Hadley branch)? -The ice clouds in polar hood are responsible for this inversion? -Influence of topography (Alba Patera)?

5 25N N 47N 2 3 Altitude, km N 4 55N 5 H2O ice Examples of measured and synthetic spectra and temperature profiles, retrieved from those spectra. H20 ice band is appeared in the spectrum at 47N. Edge of polar hood is here. Temperature profiles 2-5 have inversion at around 10 km. It s s amplitude exceeds 20K (in case 4, 5).

6 1. Late winter. Orbits 20 and 68 O68, Ls=342 Thermal inversion in the N interval is a result of influence of topography (Alba Patera on orbit 68)?? O20, Ls=335 Orbit 20 has flat topography, but temperature inversion is also observed >40 N

7 Are the H2O clouds of polar hood responsible for this temperature inversion?? O68,Ls=342 O262 Ls=13 On orbit 262 elevated thermal inversion disappeared, however Northern polar hood (H2O clouds) exists and position of the edge of polar cap is conserved. It means that thermal inversion doesn t t depend on these parameters.

8 1-58N -lg (P, mb) Temperature, K Altitude, km 2 66N 3 72N 4 85N Temperature profiles, obtained from the spectra on orbit 68. Dash-dotted lines mark the temperature of the H2O condensation corresponding to abundance of 0.1, 1, 10, 100, 200, 300 and 400 ppm respectively. Dashed line shows the temperature of the CO2 condensation. At φ>70ºn (curves 3,4) the CO2 condensation is observed in the atmosphere below 20 km.

9 Structure of the Martian atmosphere in the Northern polar region and O2 emission and O3 apparent abundance at late winter. OMEGA and PFS experiments. Zasova L.V., Altieri F, Formisano V., Bibring J-P, Bellucci G., Ignatiev N.I., D. Grassi, Giuranna M. Maturilli A (poster) O2 emission Depth of the 1.52 µm H2O ice band Depth of the 1.43 µm CO2 ice band Apparent abundance of the O3 60N 0 7 µm atm Terminator at φ >70N condensation of the CO2 below 20 km is observed 88N

10 Ice H2O O2 Ice CO2 Position of the bands, for which the images in preliminary slide are shown

11 O68, Ls=342 Tharsis Comparison of temperature fields in N-polar N region from spring equinox (northern late winter) to winter solstice (northern summer) O262 Ls=13 O588 Ls=47 O912, Ls=96

12 O103 Ls= S-pole South polar region O438 Ls=38 O913 Ls=97 terminator Arsia Mons

North and South polar regions ns together with the synthetic ones Lower two polar spectra are North (summer) and South (late summer). r).

13 North polar region South polar region o68, Φ=85º,, Ls=342º, θ =99º o913,φ=-79 79º,, Ls=97º, θ =115º o262, Φ=75º,, Ls=13º, θ =69º o438,φ=-77 77º,, Ls=38º, θ =98º o588,φ=75 =75º,, Ls=57º, θ =77º o103,φ=-85 85º,, Ls=348º, θ =89º o912, Φ=85º,, Ls=96º, θ =76º o30,φ=-86 86º,, Ls=336º, θ =76º Examples of the spectra, observed at North and South polar regions ns together with the synthetic ones Lower two polar spectra are North (summer) and South (late summer). r). In the case of the North pole the presence of water ice on the surface corresponds to the H2O O abundance of ppm. At South pole the surface temperature shows that the CO2 ice on the surface exists.

14 Conclusion Elevated temperature inversion at around 10 km of altitude with temperature maximum around 20 km was found at latitudes > 40 ºN N near spring equinox This inversion is connected to descending branch of Hadley cell l and it disappeared when circulation changes (at Ls=13 it wasn t t observed) Surface temperature at 85 N at Ls =97 is of K, which correspond to Psat (H2O) of ppm Wave structures are observed in OMEGA images on orbit 68 (O2 emission, CO2 and H2O clouds, apparent abundance of O3) in the latitude range from 70N to 80N (up to terminator). They are observed in the region where the CO2 2 clouds present in the atmosphere. The temperature profiles, obtained from the PFS LWC data, show that the CO2 condensation in the atmosphere may occur on the e day side.

Summary. Introduction. Rationale for morning observations The morning atmosphere in N spring. Conclusions. The PFS experiment Physics of PFS data

Summary. Introduction. Rationale for morning observations The morning atmosphere in N spring. Conclusions. The PFS experiment Physics of PFS data Martian morning atmosphere during Northern spring from the Planetary Fourier Spectrometer (PFS) measurements D. Grassi(1), C. Fiorenza (1,2), N.I. Ignatiev(3,1), L.V. Zasova(3,1), A. Maturilli(5,1,4),