Biomarkers in terrestrial planet atmospheres Super-Earths & Life a fascinating

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

5. NEXT STEP NOW

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

8. Visible spectrum of Earth Chlorophyll ? Water H2O Rayleigh Oxygen O2 Ozone O3 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

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

11. Thermal structure rocky Exo-P atmosphere EUV • well mixed, dry transparent atmosphere ∂T/∂z = -g/cp  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) O3: A) stratosphere high-atmosphere: 10-2 - 10-4 Pa: EUV (λ < 200 nm) photolyse any molecules, heats low density gas : B) thermosphere ~10-4 -Pa Altitude Temperature

12. Titan Earth Earth Giants Titan

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

14. Transit Geometry h ≈ T/(g m) z T( z, ) h is the effective height of an opaque atmosphere: h() = ∫ (1-T) dz So R() = R0 + h()

15. Explore Planets - EGP 2007 + Atmosphere by transits... HD189733b (Tinetti07, Swain08) Earth (Palle 09, Kaltenegger 09)

16. Earth Primary Transit: collect transmitted starlight 2002/2014+ ? Kaltenegger & Traub ApJ 2009 Palle et al. Nature 2009 Data: ATMOS B. Irion 2002 SNR = N1/2(tot) * 2Rp h / Rs2

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 SPECTRAL FINGERPRINT LIFE ? ATMOSPHERE INTERIOR FIND WHAT KIND FORMATION

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

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

22. Different evolution state / age / mass / etc.

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

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

26. VIS (0.4-1.2 mm): Res = 150 Kaltenegger et al 2007 ApJ

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. 1981 Ts ↓ water cycle ↓ weathering ↓ Ts ↑ Greenhouse effect ↑ PCO2 ↑

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 ZoneGl 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)

33. Gl 581d spectra& star/planet contrast ratioKaltenegger, Mohanty & Segura ApJ 2010Spectra (0.1 - 100 mm): Resolution 150

34. Gl 581d Transit Spectrain planetary radius Kaltenegger, Mohanty & Segura ApJ 2010Spectra (0.4 - 40 mm): Resolution 150

35. Exo-P = current students Sarah Rugheimer, Harvard, Astroph. Leah Kilvert, Un. Victoria, Astroph. Wade Henning, Harvard, EPS Roger Fu, Harvard, EPS 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)) • Not just FIND... (POS VIEW  ) • Characterize rocky exoplanets • composition 0– 20 years • habitability 5 – 20years • stage of evolution 5 – 30 years • geochemical cycles 5 – 20 years • HR Diagram of planets 5 – 20 years Are there other worlds like ours? Epicurius (c. 300 B.C) 2300 years and counting.... Let‘s find out

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 CO2 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%) H2O O3 CO2 CH4 Kaltenegger, Segura, Mohanty ApJ sub (ApJ)