biomarkers in terrestrial planet atmospheres super-earths & life a fascinating
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Biomarkers in terrestrial planet atmospheres Super-Earths & Life a fascinating cross-disciplinary puzzle. Lisa Kaltenegger MPIA/Harvard University IAUS276, Oct 15, 2010. The Pale Blue Dot Voyager image, 4 billion km away. a dot of light = astronomy. - PowerPoint PPT PresentationTRANSCRIPT
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Biomarkers in terrestrial planet atmospheres
Super-Earths & Life
a fascinating cross-disciplinary puzzle
Lisa KalteneggerMPIA/Harvard UniversityIAUS276, Oct 15, 2010
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The Pale Blue Dot
Voyager image, 4 billion km away
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a dot of light = astronomyWe will never know how to study by any means the chemical composition of starsAuguste Comte (1835)
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RV & Transits: density
Torres 2008
Fortney, 2007Sasselov 2007
Zeng & Sasselov (in press)
5NEXT STEP NOW
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Signs Of Life On An Earth-like Planet
Vegetation ?
Plantproduct
Surface features e.g.Plantlife
Bacteria
ob
serv
ed
WaterOxygen Carbon
dioxide
Methane
Nitrousoxide
Ozone
Needed for life
Primordial; & bacteria product
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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 O3
Chlorophyll ?
Oxygen O2
Water H2O
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Earth IR-emission
Kaltenegger, Traub, Jucks 2007 (ApJ)
TES data; Christensen 2004
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Thermal structure rocky Exo-P atmosphere• 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
Temperature
Alti
tude
~10-4 -Pa
EUV
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TitanEarth
Giants
Titan
Earth
13Selsis 2007 (model Tinetti)
Features: 1) observables & 2) unique ?
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Transit Geometryz
T( z, )
h is the effective height of an opaque
atmosphere:
h() = ∫ (1-T) dz
SoR() = R0 + h()
h ≈ T/(g )
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Explore Planets - EGP
Atmosphere by transits... HD189733b (Tinetti07, Swain08)Earth (Palle 09, Kaltenegger 09)
2007 +
16Kaltenegger & Traub ApJ 2009Palle et al. Nature 2009Data: ATMOS B. Irion 2002
Earth Primary Transit: collect transmitted starlight
SNR = N1/2(tot) * 2Rp h / Rs2
2002/2014+ ?
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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.
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JWST Best Earths: Closest Stars/Transit
Kaltenegger & Traub ApJ 2009
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Line of Evidence
FIND
INTERIOR
ATMOSPHERE
LIFE ?
SPECTRAL FINGERPRINT
WHAT KIND
FORMATION
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MODEL
STAR: FluxPLANET:
CompositionWater delivery OutgassingTectonicGeoch. CycleMagnetosphere
= ATMOSPHERES
SPECTRAL Fingerprint
DATA
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Gravity, size, composition LK
• Photochem• (based on Kasting 1986)
• Extended Photochemistry (based on Pavlov 2000)
• Radiative Transfer • (based on SAO98, Traub & Stier 1979)
LK
LK
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 CodeL. Kaltenegger
Detectable features
Different evolution state / age / mass / etc.
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Biomarkers & spectra change over time IMPORTANT: e.g: Surface temp change, cloud! coverage
Kaltenegger et al ApJ 2007
25Kaltenegger et al 2007 ApJmid IR (5-20m): Res = 25
26Kaltenegger et al 2007 ApJ
VIS (0.4-1.2 m): Res = 150
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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,...
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Climate Stabilization : Carbonate – Silicate Cycle Walker et al. 1981
Ts ↓ water cycle ↓ weathering ↓
Ts ↑ Greenhouse effect ↑ PCO2 ↑
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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)
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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,...
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Test case: Gl 581d
Kaltenegger, Segura & Mohanty 2010 (ApJ)
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Test case: Gl 581d
Kaltenegger, Segura & Mohanty 2009 (ApJ)
Gl 581d spectra& star/planet contrast ratioKaltenegger, Mohanty & Segura ApJ 2010
Spectra (0.1 - 100 m): Resolution 15033
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Gl 581d Transit Spectrain planetary radius Kaltenegger, Mohanty & Segura ApJ 2010Spectra (0.4 - 40 m): Resolution 150
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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 posMPIA Heidelberg
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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
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WHY ?
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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
CreditNAI, Harvard Origins of Life
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Super Earth around M star HZGl 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%)
CO2
O3
CH4
H2OCO2
Kaltenegger, Segura, Mohanty ApJ sub (ApJ)