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

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

-Earthlike biomass -one bar surface pressure -vary gravity (1g, 3g) -vary M-star class (M0 to M7)

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

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

Source: 2D Model SOCRATES Altitude (km)‏ Atmospheric Biomarkers: Earth's Ozone Layer Ozone (O 3 ) produced from oxygen which itself comes mainly from biology...so ozone is a biomarker (life-indicator). Ozone is easier to detect spectrally than oxygen. „Good“ Ozone O 2 +UV-->O+O NEED UVB O+O 2 +M-->O 3 +M „Bad“ Ozone – smog ~9ppm

“Bad” (Smog) Ozone formed: CO+2O 2 -->O 3 +CO 2 “Good” Ozone formed: O 2 +hv--> 2O O 2 +O+M-->O 3 +M 30km 10km ~9x10 -6 by volume Height Ozone Concentration Chlorine reactions destroy ozone Nitrogen reactions destroy ozone Ozone in Earth's Atmosphere 30km 70k m OZONE CONTINUOUSLY FORMED AND DESTROYED

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 submitted)‏ CLIMATE ground to mid- mesosphere Stratosphere Solve Radiative Transfer Troposphere Wet adiabatic convection CHEMISTRY ground to mid- mesosphere Solve Continuity Eq. 55 species 220 reactions Biomarker chemistry Start values Start Values Temperature, water Radiative Gases

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 submitted)‏ CLIMATE ground to mid- mesosphere Stratosphere Solve Radiative Transfer Troposphere Wet adiabatic convection CHEMISTRY ground to mid- mesosphere Solve Continuity Eq. 55 species 220 reactions Biomarker chemistry Start values Start Values Temperature, water Radiative Gases OUTPUT TO LINE-BY-LINE SPECTRAL EMISSION MODEL (SQuIRRL) (Schreier and Böttger, 2003)

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

30km 10km Height Ozone Concentration Chlorine reactions destroy ozone HOW PAP WORKS Cl+O 3 -->ClO+O 2 ClO+O-->Cl+O O 3 +O-->2O 2 5% O 3 loss 30km

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

Results: Effect of Stellar Spectrum on Temperature M8 M0 ADL Earth M7 M6 M5 RESULTS: Effect of M-Star Class on Planetary Temperature Profile Less UV-B: less jH 2 O, less OH, more CH 4 (and H 2 O)  Stratospheric Heating M4

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

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

Grenfell et al. Paper II: OZONE RESPONSES Column (Production – Loss) in molecules cm -2 Earth Earthlike around M7 star 2E12 4E10 PRODUCTION O 2 +hv-->O+O O+O 2 +M-->O 3 +M CHAPMAN (99%)‏ PRODUCTION CO+2O 2 -->O 3 +CO 2 SMOG (~50%) LOSS O 3 +CO-->O 2 +CO 2 O 3 REDUCTION (~35%)‏ Grenfell et al. (2010) in preparation LOSS NOx, HOx destruction CLASSIC CYCLES (~50%)‏

Grenfell et al. Paper II: OZONE RESPONSES Column (Production – Loss) in molecules cm -2 Earth Earthlike around M7 star 2E12 4E10 PRODUCTION O 2 +hv-->O+O O+O 2 +M-->O 3 +M CHAPMAN (99%)‏ PRODUCTION CO+2O 2 -->O 3 +CO 2 SMOG (~50%) LOSS O 3 +CO-->O 2 +CO 2 O 3 REDUCTION (~35%)‏ Grenfell et al. (2010) in preparation LOSS NOx, HOx destruction CLASSIC CYCLES (~50%)‏ Weaker UV-B from M-star means Chapman production (needs jO 2 ) - fails M7 Ozone produced from smog mechanism

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