Exoplanet Atmosphere Characterization & Biomarkers

Transcription

1 Giovanna Tinetti ESA/Institut d Astrophysique de Paris γ Exoplanet Atmosphere Characterization & Biomarkers

2 Can we use Remote Sensing Spectroscopy, - Interaction between photon coming from the parent star and planet to characterize Extrasolar Planets?

3 NASA TPF-C ~2025 (0.5 ( μm) EPIC, ECLIPSE, SEE, etc. Photons reflected by the planet VIS-NIR γ Surface albedo /biosignatures + Atmospheric molecules (electronic transition) + Cloud properties

4 NASA TPF-C ~2025 (0.5 EPIC, ECLIPSE, SEE, etc. Spitzer, NASA TPF-I ESA Darwin ~2025 (6.5 ( μm) (6.5-17μm) Photons reflected by the planet VIS-NIR Photons emitted by the planet MIR γ γ Atmospheric/Surface thermal properties + Atmospheric molecules (roto-vibrational modes) + Clouds

5 NASA TPF ~2025 (0.5 TPF-C ( μm) EPIC, ECLIPSE, SEE, etc. Photons reflected by the planet VIS-NIR γ Spitzer, NASA TPF-I ESA Darwin ~2025 (6.5 (6.5-17μm) Photons emitted by the planet MIR γ HST, Spitzer, JWST telescopes Photons transmitted by the planet UV-VIS VIS-IRIR γ

6 Learning from our solar system You are here!

7 Terrestrial Planet planets Spectra in our Solar Vary System offer Widely diverse in spectra Solar which System aid in their characterization.? CO 2 CO 2 VENUS X 0.60 EARTH-CIRRUS O 2 H 2 O H 2 O H 2 O H 2 O O 3 O 2 Iron oxides MARS EARTH-OCEAN H 2 O ice

8 Searching for other Planets in the Galaxy You are here!

9 Chemistry Radiative transfer Climate + Cloud Escape processes Internal structure

10 Averaging over disk and time Extrasolar planet characterization missions Tinetti et al, Astrobiology 2005, 2006

11 Generating spectra Input to the models Satellite data or GCMs Cloud pattern Carbon dioxide images from PNNL, in microns Line lists Surface reflectance Run radiative transfer algorithms to describe the complex interaction of the photon with the atmosphere and the surface of the planet Thermal Stellar Resolution needed to resolve the disk Use specific models to create the Disk-averaged spectra

12 Disk-averaged Earth spectra: VIS Model Earthshine data (Woolf et al. 2002) Tinetti,et al, 2006

13 Disk-averaged Earth spectra: NIR Tinetti,et al, 2006 Model Mars Omega Express data

14 Disk-averaged Earth spectra: NIR Tinetti,et al, Astrobiology, 2006 Model Mars Omega Express data

15 Disk-averaged Earth spectra: IR Mars Global Surveyor-TES data from (Christensen, Pearl, 1997) Tinetti,et al, Astrobiology, 2006, vol. 6, n. 1

16 T=5800K Clever vegetation! γ T~ 288 K (Nelson & Cox 2000)

17 The Red-edge:a edge:a naturally Amplified Signal Arnold et al, 2002; Seager et al., 2005; (Gates 1965, adapted) Montanes-Rodriguez et al., 2005

18 Vegetation in the diurnal cycle Earth, clear sky case Earth with clouds ~40% Red-edge band Low clouds on Ocean iddle clouds on Polar regions Earth disk-averaged spectra, detectability of surface biosignatures for TPF-C Tinetti et al. 2006, Astrobiology

19 Vegetation in the diurnal cycle Earth, clear sky case Earth with clouds ~40% Red-edge band Red-edge band High clouds central America -Low clouds and middle clouds can be false positive for Red-Edge in some phases

20 Vegetation in the diurnal cycle Earth, clear sky case Earth with clouds Red-edge band Red-edge band High clouds central Africa & Asia

21 Vegetation in the diurnal cycle Earth, clear sky case Earth with clouds ~40% Red-edge band Red-edge band High clouds in Asia

22 Disk-averaged spectra with only one surface type Ocean NDVI= Grass 0.34 Forest 0.4 Tundra R NIR Desert Ice Cirrus cloud < 0 Cumulus cloud < 0 Stratus cloud < 0 NDVI = (NIR R) / (NIR + R)

23 Vegetation versus cloud For all phases, NDVI is a useful index to discriminate vegetated areas. Problems with fully illuminated (unobservable!) when clouds are present. ~40% vegetation? Caveat: On an extrasolar terrestrial planet the red-edge might be red-shifted, The cloud microphysics/scattering properties might be different

24 Red-edge edge shifted Clear sky Realistic cloud pattern Shifted Red-edge G. Tinetti, S. Rashby, Y. Yung,2006,Apj

25 Leaf model & shifted Red-edge edge 3-photon photosynthetic scheme (Wolstencroft( and Raven, 2002) Optical model of plant leaves (Jacquemoud & Baret 1990) Modified pigment absorption properties Output: whole leaf spectrum shifted to longer wavelengths

26 Clear sky Planetary model Planet tidally locked 80% CO2 22% Low Clouds+ 25% Middle Clouds+ 25% High Clouds GCM T-P profile (Joshi 2003) Realistic cloud pattern Tinetti, Rashby, Yung, Apj, 2006

27 Clear sky Simulated spectrum Exovegetation on the illuminated side Realistic cloud pattern Tinetti, Rashby, Yung, Apj, 2006

28 Plankton? Plankton is challenging to detect, even with clear sky

29 Plankton with clouds Too hard for modern Earth concentrations! Tinetti et al., 2006, Astrobiology

30 Stellar occultation Impact parameter Height You are here Atmosphere

31 HD : the atmosphere (Charbonneau et al. 2002) ±0.0057% ±0.0038% Explanations: clouds and ionisation (Brown, 2001; Fortney et al. 2003) or condensation Na to Na2S on the dark side (Iro et al. 2005, Tinetti et al. 2006)

32 An extended upper atmosphere around the extrasolar planet HD209458b A. Vidal-Madjar (IAP) A. Lecavelier des Étangs (IAP) J.-M. Désert (IAP) G. E. Ballester (Univ. Arizona) R. Ferlet (IAP) G. Hébrard (IAP) M. Mayor (Obs. Genève) Nature 422, 143, 2003

33 Evaporation rate > g/s => Taux d évaporation > g s ±4%

34 Wavelength (Å) Detection of Carbon & Oxygen Outside Transit During Transit Carbon Oxygen Vidal-Madjar et al (astro-ph/ ) ~13 % ~8 % ±4.5 % ±3.5 %

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36 Transmission spectra of Hot Jupiters in the IR CO HO 2 HD183733b simulations with different C/O ratios CO H O Tinetti et al., Apj,, submitted

37 Earth-like planet in transit Spectrum ratio = F star+planet /F star -1 Ehrenreich D., Tinetti G., et al., A&A, 448, 2006, CO 2 O 3 H O 2 O H 2 O 2 O H 2 O 2 CO2

38 Venus-like planet in transit Spectrum ratio = F star+planet /F star -1 Ehrenreich D., Tinetti G., et al., A&A, 448, 2006,

39 Ocean planet in transit Spectrum ratio = F star+planet /F star -1 Ehrenreich D., Tinetti G., et al., A&A, 448, 2006,

40 Earth-size exoplanets in transit Volatile-rich planets are favored Late type stars are favored (better S/N, more numerous) Atmosphere of Earth-size planet might be detectable with 10-40m telescope, dep. on target Technique more sensitive to upper part of the atmosphere Ehrenreich D., Tinetti G.,et al., 2006, A&A

41 Observational geometry Planetary Modeling Spectral Retrieval

42 Chemistry Radiative transfer Climate + Cloud Escape processes Internal structure

43 4D-Spectral Retrieval: the inverse problem Direct 3D model + Genetic Algorithm & Simulated Annealing 100% 90% 80% Retrieved Albedo Configuratio High cloud Medium cloud Low cloud Ice Ground Tundra Grass Forest Ocean 70% 60% 50% 40% 30% 20% 10% 0% Cluster Center ID Terrile, Lee, Tinetti,et al., 2006

44 Evaluation of the Degeneracy Terrile, Lee, Tinetti,et al., 2006

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46 Disk-time averaged spectra Average over the day Fully illuminated/cloudy Red-edge Band Dichotomy/cloudy Fully illuminated/clear sky

47 Following the planet during its orbit

48 Temporal Atmospheric Signatures On the Earth CH 4 and CO 2 both breathe with the seasons. Volcanic activity? CO2 cycle on Mars

49 CH 4 H 2 O N 2 O Annual cycle, surface temperature Annual cycle, 1m-underground temperature Earth on an eccentric orbit: ε = 0.4, θ=45

50 Temporal surface signatures Polar cap variation are detectable in the Mars disk-averaged spectra No Polar caps 50 o extension 70 o extension Totally frozen Mars VIS+NIR

51 Sensitivity to Viewing geometry Clear sky (summer) Clouds (summer) VIS Tinetti et al.,2006

52 Sensitivity to Viewing geometry Clear sky (summer) Clouds (summer) NIR

53 Sensitivity to Viewing geometry Clear sky (summer) Clouds (summer) IR

54 Sensitivity to Phases Earth disk-averaged spectra, 3D model, study for TPF-C Cloud-less disk-averaged spectrum Realistic clouds 100% Strato-cumulus clouds 100% Alto-stratus clouds 100% Cirrus clouds Tinetti et al.,2006

55 Ice versus silicate: : why do we care? Terre Planète-Océan Sotin, Grasset and Mocquet

56 Radius/mass ratio Sotin, Grasset and Mocquet

57 Carbon planets: do they exist? Radius/mass different Atmosphere C rich (more CO than H 2 O!!) Kuchner, Seager

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60 Rayleigh Scattering Size parameter ~ a/λ where a: Gas molecules ~ 10-4 um Aerosol ~ 1 um Water droplets~ 10 um Ice crystals ~ 100 um Pressure Composition Surface reflectivity

61 Sensitivity to Pressure 1 and 2 bar Earth atmosphere: deeper absorption features

62 VIS Earth detection by TPF R=70 O 2 H 2 O H 2 O TPF simulation by T. Velusamy H 2 O CH 4 O 3 IR CO 2 R=100 R=20