1 Biomarkers in terrestrial planet atmospheres Super-Earths & Life a fascinating cross-disciplinary puzzle Lisa Kaltenegger MPIA/Harvard University IAUS276, Oct 15, 2010

2 The Pale Blue Dot Voyager image, 4 billion km away

3 a dot of light = astronomy We will never know how to study by any means the chemical composition of stars Auguste Comte (1835)

4 RV & Transits : density Torres 2008 Fortney, 2007 Sasselov 2007 Zeng & Sasselov (in press)

5 NEXT STEPNOW

6 Signs Of Life On An Earth-like Planet Vegetation ? Plant product Surface features e.g. Plant life Bacteria observed Water Oxygen Carbon dioxide Methane Nitrous oxide Ozone Needed for life Primordial; & bacteria product

7

8 Visible spectrum of Earth Observed Earthshine, reflected from dark side of moon. Ref.: Kaltenegger et al 2007, ApJ 574, 2007 see also e.g.: Montanez-Rodrigez 2005, 07, Arnold 2002, 06, 09; Turnbull 06 Rayleigh Ozone O 3 Chlorophyll ? Oxygen O 2 Water H 2 O

9 Earth IR-emission Kaltenegger, Traub, Jucks 2007 (ApJ) TES data; Christensen 2004

10

11 Thermal structure rocky Exo-P atmosphere well mixed, dry transparent atmosphere ∂T/∂z = -g/c p  convection Earth : -9.8 K/km, Mars -5 K/km, Venus -10 K/km, Titan 1.3 K/km REALITY: atmosphere absorbs & reemits in thermal IR Radiative equilibrium profile & convection mid-atmosphere: UV (λ < 360 nm) O 3 : A) stratosphere high-atmosphere: Pa: EUV (λ < 200 nm) photolyse any molecules, heats low density gas : B) thermosphere Temperature Altitude ~ Pa EUV

12 Titan Earth Giants Titan Earth

13 Selsis 2007 (model Tinetti) Features: 1) observables & 2) unique ?

14 Transit Geometry z T( z, ) h is the effective height of an opaque atmosphere: h( ) = ∫ (1-T) dz So R( ) = R 0 + h( ) h ≈ T/(g  )

15 Explore Planets - EGP Atmosphere by transits... HD189733b (Tinetti07, Swain08) Earth (Palle 09, Kaltenegger 09)

16 Kaltenegger & Traub ApJ 2009 Palle et al. Nature 2009 Data: ATMOS B. Irion 2002 Earth Primary Transit: collect transmitted starlight SNR = N 1/2 (tot) * 2  R p h /  R s /2014+ ?

17 Earth: ATMOS-3:Transmission validation in far-IR ATMOS-3 transmission of sunlight through Earth’s atmosphere, measured with a fast FTS on Shuttle yellow = model Fit is close, but line wings are not perfect, perhaps owing to line- mixing effects in strong bands. Note low transmission below 10 km.

18 JWST Best Earths: Closest Stars/Transit Kaltenegger & Traub ApJ 2009

19 Line of Evidence FIND INTERIOR ATMOSPHERE LIFE ? SPECTRAL FINGERPRINT WHAT KIND FORMATION

20 MODEL STAR: Flux PLANET: Composition Water delivery Outgassing Tectonic Geoch. Cycle Magnetosphere = ATMOSPHERES SPECTRAL Fingerprint DATA

21 Gravity, size, composition LK Photochem (based on Kasting 1986) Extended Photochemistry (based on Pavlov 2000) Radiative Transfer (based on SAO98, Traub & Stier 1979) LK Planet interior,outgassing RF,WH biota, host stars, geo.cycles SR,LK Clouds, Hazes, Escape Kaltenegger et al 2007, 2009, 2009b ApJ Exo-P = Rocky ExoPlanets Code L. Kaltenegger Detectable features

Different evolution state / age / mass / etc.

23

24 Biomarkers & spectra change over time IMPORTANT: e.g: Surface temp change, cloud! coverage Kaltenegger et al ApJ 2007

25 Kaltenegger et al 2007 ApJ mid IR (5-20  m): Res = 25

26 Kaltenegger et al 2007 ApJ VIS (  m): Res = 150

27 Habitable Zone – water liquid on surface of Earth-analog Selsis et al 2007, Kaltenegger et al 2008, Seager et al 2008, Miller-Ricci et al 2008,...

28 Climate Stabilization : Carbonate – Silicate Cycle Walker et al Ts ↓ water cycle ↓ weathering ↓ Ts ↑ Greenhouse effect ↑ P CO2 ↑

29 Pinatubo – explosive exo-volcanos ? Res = 150, SNR calc. for JWST (pure photon noise, template input for instruments) Kaltenegger & Sasselov (ApJ 09), Kaltenegger & Henning (ApJ 2010)

30 Goldilocks Zone Gl 581c... HOT, Gl581d COLD Selsis et al 2007, Kaltenegger et al 2010, von Paris et al 2010, Seager et al 2008, Miller-Ricci et al 2008,...

31 Test case: Gl 581d Kaltenegger, Segura & Mohanty 2010 (ApJ)

32 Test case: Gl 581d Kaltenegger, Segura & Mohanty 2009 (ApJ)

Gl 581d spectra & star/planet contrast ratio Kaltenegger, Mohanty & Segura ApJ 2010 Spectra (  m): Resolution

34 Gl 581d Transit Spectra in planetary radius Kaltenegger, Mohanty & Segura ApJ 2010 Spectra (  m): Resolution 150

35 Wade Henning, Harvard, EPS Roger Fu, Harvard, EPS Sarah Rugheimer, Harvard, Astroph. Leah Kilvert, Un. Victoria, Astroph. Exo-P = current students OPEN (AAS job registry): 2 Postdoc & 1 PhD pos MPIA Heidelberg

36 Science Case: ELT,GMT,TMT, JWST (SPITZER, SPICA, SMALL SPACE MISSIONS (e.g TESS) ) Are there other worlds like ours? Epicurius (c. 300 B.C) 2300 years and counting.... Let‘s find out Not just FIND... (POS VIEW ) Characterize rocky exoplanets - composition 0 – 20 years - habitability 5 – 20 years - stage of evolution 5 – 30 years - geochemical cycles 5 – 20 years - HR Diagram of planets 5 – 20 years

37 WHY ?

38 Summary First potentially Habitable Super-Earth found JWST, ELT/GMT/TMT & new small missions Models: - instrument design, data analysis - explore the underlying physics Earth: a rosetta stone for exoplanets Credit NAI, Harvard Origins of Life

39 Super Earth around M star HZ Gl 581d: Earth Atmosphere, 2.63 bar, 1.8x Earth gravity Tidally locked planet (rapidely rotating planet comparison line (shown in grey)) Scenario 1: high heat transport from day (60%) to night side (40%) CO 2 O3O3 CH 4 H2OH2O CO 2 Kaltenegger, Segura, Mohanty ApJ sub (ApJ)