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Biomarkers in Super Earth Atmospheres: Photochemical Responses

Biomarkers in Super Earth Atmospheres: Photochemical Responses. John Lee Grenfell Zentrum f ür Astronomie und Astrophysik, Technische Universit ät (TU) Berlin.

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Biomarkers in Super Earth Atmospheres: Photochemical Responses

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  1. Biomarkers in Super Earth Atmospheres: Photochemical Responses John Lee Grenfell Zentrum für Astronomie und Astrophysik, Technische Universität (TU) Berlin 1,2Rauer, H.,1Gebauer, S., 2v, Paris, P.,2Cabrera, J.,1Godolt, M.,1Palczynski, K. 3Belu, A.,3Selsis, F.,3 Hedelt, P. (1) TU-Berlin, (2) German Space Agency (DLR-PF) Berlin, (3) Uni. Bordeaux

  2. Grenfell et al. II. Chemical Responses (in preparation)

  3. -Earthlike biomass -one bar surface pressure -vary gravity (1g, 3g) -vary M-star class (M0 to M7) Grenfell et al. II. Chemical Responses (in preparation)

  4. Overview of Talk • Motivation • Ozone as an atmospheric biomarker • Models and tools • Super-Earth scenarios • Results • Conclusions

  5. Motivation Understand and predict atmospheric spectra of Super-Earth planets in the HZ of M-stars

  6. Atmospheric Biomarkers: Earth's Ozone Layer Ozone (O3) produced from oxygen which itself comes mainly from biology ...so ozone is a biomarker (life-indicator). Ozone is easier to detect spectrally than oxygen. Altitude (km)‏ „Good“ Ozone O2+UV-->O+O NEED UVB O+O2+M-->O3+M ~9ppm „Bad“ Ozone – smog Source: 2D Model SOCRATES

  7. Ozone in Earth's Atmosphere OZONE CONTINUOUSLY FORMED AND DESTROYED 70km “Good” Ozone formed: O2 +hv--> 2O O2+O+M-->O3+M Height Chlorine reactions destroy ozone 30km 30km Nitrogen reactions destroy ozone 10km “Bad” (Smog) Ozone formed: CO+2O2-->O3+CO2 Ozone Concentration ~9x10-6 by volume

  8. MODELS AND TOOLS: CLIMATE-CHEMISTRY MODEL Global Mean Column Model with coupled radiation and chemistry (Kasting et al., 1984, Segura et al., 2003; Grenfell et al., 2007: Rauer et al. 2010 submitted)‏ Radiative Gases CHEMISTRY ground to mid-mesosphere Solve Continuity Eq. 55 species 220 reactions Biomarker chemistry Start values CLIMATE ground to mid-mesosphere Stratosphere Solve Radiative Transfer Troposphere Wet adiabatic convection Start Values Temperature, water

  9. MODELS AND TOOLS: CLIMATE-CHEMISTRY MODEL Global Mean Column Model with coupled radiation and chemistry (Kasting et al., 1984, Segura et al., 2003; Grenfell et al., 2007: Rauer et al. 2010 submitted)‏ Radiative Gases CHEMISTRY ground to mid-mesosphere Solve Continuity Eq. 55 species 220 reactions Biomarker chemistry Start values OUTPUT TO LINE-BY-LINE SPECTRAL EMISSION MODEL (SQuIRRL) (Schreier and Böttger, 2003) CLIMATE ground to mid-mesosphere Stratosphere Solve Radiative Transfer Troposphere Wet adiabatic convection Start Values Temperature, water

  10. Pathway Analysis Program (PAP)‏ Atmospheric model: chemical rates and concentrations over two timesteps PAP Identify and quantify chemical pathways for e.g. ozone Hence understand changes in ozone photochemistry Lehmann 2004 Grenfell et al. (2006)‏

  11. HOW PAP WORKS Cl+O3-->ClO+O2 ClO+O-->Cl+O2 ---------------------- O3+O-->2O2 5% O3 loss 30km Height Chlorine reactions destroy ozone 30km 10km Ozone Concentration

  12. Super-Earth Scenarios M0 3800K M4.5 3400K Earth (M)‏ 10M (3g)‏ Assume an Earthlike development Rauer et al. (2010) submitted Grenfell et al. (2010) in preparation M8 2400K

  13. Results: Effect of Stellar Spectrum on Temperature RESULTS: Effect of M-Star Class on Planetary Temperature Profile Less UV-B: less jH2O, less OH, more CH4 (and H2O)  Stratospheric Heating M7 M6 M5 ADL M4 M0 M8 Earth

  14. RESULTS: Effect on Ozone of changing M-star spectrum Sun M0 M0 M7 M7 -higher spectral class -less UV -less ozone warmer stratosphere, so faster Chapman sink: O+O32O2 Rauer et al. (2010) submitted

  15. Effect on Ozone of increasing gravity Results: Effect on Ozone of Increasing Gravity Super-Earth (3g)‏ 3g 1g Earth Rauer et al. (2010) submitted

  16. Grenfell et al. Paper II: OZONE RESPONSES Column (Production – Loss) in molecules cm-2 Earth Earthlike around M7 star 2E124E10 PRODUCTION CO+2O2-->O3+CO2 SMOG (~50%) PRODUCTION O2+hv-->O+O O+O2+M-->O3+M CHAPMAN (99%)‏ LOSS O3+CO-->O2+CO2 O3 REDUCTION (~35%)‏ LOSS NOx, HOx destruction CLASSIC CYCLES (~50%)‏ Grenfell et al. (2010) in preparation

  17. Grenfell et al. Paper II: OZONE RESPONSES Column (Production – Loss) in molecules cm-2 Earth Earthlike around M7 star 2E124E10 Weaker UV-B from M-star means Chapman production (needs jO2) - fails M7 Ozone produced from smog mechanism PRODUCTION CO+2O2-->O3+CO2 SMOG (~50%) PRODUCTION O2+hv-->O+O O+O2+M-->O3+M CHAPMAN (99%)‏ LOSS O3+CO-->O2+CO2 O3 REDUCTION (~35%)‏ LOSS NOx, HOx destruction CLASSIC CYCLES (~50%)‏ Grenfell et al. (2010) in preparation

  18. Conclusions • Essential to couple climate and chemistry • Ozone photochemistry may be smog-dominated • (whereas Chapman-dominated on Earth) for earthlike • planets in the Habitable Zone of M-stars

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