A window to transiting exoplanet characterization. Observations and modeling of Earth’s transmission spectrum through lunar eclipses: A window to transiting exoplanet characterization. E. Palle, M.R. Zapatero, P. Montañes-Rodriguez, R. Barrena, A. Garcia-Muñoz

Lunar eclipse August 16th 2008

We observed the Earth transmission spectrum during a lunar eclipse NOT, Visible, 0.4-1 μm WHT, Near-IR, 0.9-2.5 μm La Palma, Canaries

A penumbral eclipse seen from the Moon Lunar explorer "KAGUYA" (SELENE) on February 10, 2009 Moon here JAXA/NHK

Umbra Penumbra Brigth Moon

Umbra/Bright Umbra Bright Hα

Earth’s Transmission Spectrum The pale red dot Palle et al, Nature, 2009

Evolution of the Earth’s Transmission Spectrum during the eclipse: ZJ

Evolution of the Earth’s Transmission Spectrum during the eclipse: O2 dimer band

Modeling efforts: Constructing a true model Earth – moon distance ∞ = exoplanets Non-radial symmetry Direct transmission Diffraction, refraction Diffuse light JAXA/NHK

Modeling efforts: The alpha value 0 0.5 0.7

Transmission models: Rayleigh atmosphere Garcia-Muñoz et al, in preparation

Transmission models: Rayleigh atmosphere Garcia-Muñoz et al, in preparation Difference

Transmission models: Rayleigh + Clouds (8km) + aerosols (Direct +Diffuse) Garcia-Muñoz et al, in preparation Diffuse light insensitive to alpha and dominant at short wavelengths

Oxygen complexes in the Earth’s atmosphere: Oxygen dimers Oxygen at visible wavelengths Intensity reversal again explained trough diffuse light contribution

Oxygen complexes in the Earth’s atmosphere: Oxygen dimers Oxygen at near-IR wavelengths O2•O2 O2•N2

Earth’s Reflectance Spectrum: Earthshine NOT, Visible, 0.4-1 μm WHT, Near-IR, 0.9-2.5 μm La Palma, Canaries 0.5 1.0 1.5 2.0 2.5 μm

Transmission Spectrum Reflected spectrum Transmission Spectrum Blue planet? O2 O2•O2 O2•N2 CH4 CO2 CH4 O2•O2 O2 CO2 0.5 1.0 1.5 2.0 2.5 μm Palle et al, 2009

M8 star + 1 Earth ... with the E-ELT Palle et al, ApJ, submitted 20, 100, 500, 1000 spectra combined - SNR 1000

M8 star + 1 Earth ... with the E-ELT Palle et al, ApJ, submitted 20, 100, 500, 1000 spectra combined - SNR 1000

Earth’s transmission spectrum in the mid-IR

More Moon Soon ... 21st December 2010: 0.3 – 24 micron VISIR @ VLT3 CRIRES @ VLT1 COMICS @ SUBARU SPEX @ IRTF Palomar & HST More Moon Soon ... 21st December 2010: 0.3 – 24 micron

Thank you

Still, we must pursue the characterization with direct observations Exploration of surface features Presence of continents Rotational period Localized surface biomarkers (vegetation) Orbital light curve Ocean glints and polarization effects

Conclusions We have obtained the Earths transmission spectra 0.4-2.5 μm First order detection and characterization of the main constituents of the Earth's atmosphere Detection of the Ionosphere : Ca II, ( Mg, Fe, ??) Detection of O2•O2 and O2•N2 interactions Offers more information than the reflectance spectra We are developing models to understand the Earth’s transmission spectrum and extend this knowledge to extrasolar transiting rocky planets Using the measured Earth transmission spectrum and several stellar spectra, we compute the probability of characterizing a transiting earth with E-ELT For a Earth in the habitability zone of an M-star, it is possible to detect H2O , O2 , CH4 ,CO2 (= Life) within a few tens of hours of observations.

Thank you

How deep we see in the planet atmosphere? h min ? Are antropogenic signatures visible in the lower layers? Is there a surface signal? Traub, 2009

But, how far are we from making the measurements ? Thus, the transmission spectrum of telluric planets contains more information for the atmospheric characterization than the reflected spectrum. And it is also less technically challenging But, how far are we from making the measurements ?

F* F* - F* ( ) + F*( ) T Aa ____ A* Ap*a ______ + Ruido + Ruido

Differential transit spectroscopy M star + Earth : 1 (2) measurement Ss+p / Sp Wavelength (μm)

Detection Perspectives ~5 h ~ 25 h ~ 50 h ~ 150 h Palle et al, ApJ, submitted

Molecular complexes in the Earth’s atmosphere: the dimers Van de Waals molecules: Weakly bound complexes They are present as minor rather than trace species. One likely origin of continuum absorption. Observed on Earth (gas) and Jupiter (gas; (H2)2), Ganymede, Europa and Callisto (condensed), and in the laboratory (gas/condensed). Never on Venus/Mars, where there must be CO2 – X NOT contained in the common spectral libraries Calo and Narcisi (1980) Their total abundance is confined to the lower scale height of the atmosphere.

H2O Ca II O3 O2 Earth’s Transmission Spectrum Visible 0.4 0.5 0.6 0.7 0.8 0.9 μm

Fraunhofer lines structure NO2 ? Ca II Hα Ca II

CO2 O2•O2 H2O Earth’s Transmission Spectrum Near-IR ZJ O2 O2•O2 O2•N2 1.0 1.25 1.5 μm

Earth’s Transmission Spectrum Near-IR HK CH4 H2O CO2 1.5 2.0 2.5 μm

The Ring effect Rotational Raman Scattering (RRS) Early evidence: Sky-scattered Fraunhofer lines were less deep but broader than solar lines Incident exiting λex-Δλ, λex, λex+Δλ frequency redistribution Incident λ + Stokes + Anti-Stokes branches incident photon λex difference/ ratio

M8 star + 1 Earth ... with the E-ELT Wavelength (μm) Wavelength (μm) Work in progress ...

The Ring effect: Rotational Raman scattering Vountas et al. (1998) Transmission spectrum Solar spectrum

Garcia-Muñoz et al, in preparation

Reflection vs Transmission

How deep we see in the planet atmosphere? Evidences? Ref.: Kaltenegger & Traub 2009

The Earthshine on the moon ES/MS = albedo (+ geometry and moon properties)

Spectral Albedo of the Earth: 2003/11/19 Rayleigh Scattering Chappuis Ozone band B-O2 A-O2 Atmospheric Water vapor Montañés-Rodriguez et al., ApJ, 2006

Kaltenegger & Traub 2009 0.5 1.0 1.5 2.0 2.5 Palle et al, 2009

CoRoT & KEPLER can provide this input Many other surveys: Plato, TESS, Ground-based searches, ... Terrestrial inner-orbit planets based on their transits: - About 50 planets if most have R ~ 1.0 Re - About 185 planets if most have R ~ 1.3 Re About 640 planets if most have R ~ 2.2 Re (Or possibly some combination of the above) About 12% of the cases with two or more planets per system

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