Biomarkers in Super Earth Atmospheres: Photochemical Responses

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

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Motivation
Understand and predict atmospheric spectra of
Super-Earth planets in the HZ of M-stars
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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 O2UV--gtOO NEED UVB
OO2M--gtO3M
9ppm
Bad Ozone smog
Source 2D Model SOCRATES
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Ozone in Earth's Atmosphere
OZONE CONTINUOUSLY FORMED AND DESTROYED
70km
Good Ozone formed O2 hv--gt 2O O2OM--gtO3M
Height
Chlorine reactions destroy ozone
30km
30km
Nitrogen reactions destroy ozone
10km
Bad (Smog) Ozone formed CO2O2--gtO3CO2
9x10-6 by volume
Ozone Concentration
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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 Sol
ve Radiative Transfer Troposphere Wet adiabatic
convection
Start Values
Temperature, water
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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 Sol
ve Radiative Transfer Troposphere Wet adiabatic
convection
Start Values
Temperature, water
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Pathway Analysis Program (PAP)?
PAP
Atmospheric model chemical rates and
concentrations over two timesteps
Identify and quantify chemical pathways for e.g.
ozone
Hence understand changes in ozone photochemistry
Lehmann 2004 Grenfell et al. (2006)?
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HOW PAP WORKS
ClO3--gtClOO2 ClOO--gtClO2 ---------------------
- O3O--gt2O2 5 O3 loss 30km
Height
Chlorine reactions destroy ozone
30km
10km
Ozone Concentration
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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
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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
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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
OO3?2O2
Rauer et al. (2010) submitted
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Effect on Ozone of increasing gravity
Results Effect on Ozone of Increasing Gravity
Super-Earth (3g)?
3g
1g
Earth
Rauer et al. (2010) submitted
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Grenfell et al. Paper II OZONE
RESPONSES Column (Production
Loss) in molecules cm-2 Earth
Earthlike around M7 star
2E12 4E10
PRODUCTION CO2O2--gtO3CO2 SMOG
(50)
PRODUCTION O2hv--gtOO OO2M--gtO3M
CHAPMAN (99)?
LOSS O3CO--gtO2CO2 O3 REDUCTION
(35)?
LOSS NOx, HOx destruction CLASSIC
CYCLES (50)?
Grenfell et al.
(2010) in preparation
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Grenfell et al. Paper II OZONE
RESPONSES Column (Production
Loss) in molecules cm-2 Earth
Earthlike around M7 star
2E12 4E10
Weaker UV-B from M-star means Chapman production
(needs jO2) - fails M7 Ozone produced from smog
mechanism
PRODUCTION CO2O2--gtO3CO2 SMOG
(50)
PRODUCTION O2hv--gtOO OO2M--gtO3M
CHAPMAN (99)?
LOSS O3CO--gtO2CO2 O3 REDUCTION
(35)?
LOSS NOx, HOx destruction CLASSIC
CYCLES (50)?
Grenfell et al.
(2010) in preparation
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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