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Spectroscopic characterization of the atmospheres of potentially habitable planets: GL 581 d as a model case study

von Paris, P. und Cabrera, J. und Godolt, M. und Grenfell, J. L. und Hedelt, P. und Rauer, Heike und Schreier, Franz und Stracke, Barbara (2011) Spectroscopic characterization of the atmospheres of potentially habitable planets: GL 581 d as a model case study. Astronomy and Astrophysics, 534 (A26), Seiten 1-11. EDP Sciences. DOI: 10.1051/00046361/201117091 ISSN 0004-6361

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Context. Were a potentially habitable planet to be discovered, the next step would be the search for an atmosphere and its characterization. Eventually, surface conditions, hence habitability, and biomarkers as indicators for life would be assessed. Aims. The super-Earth candidate Gliese (GL) 581 d is the first potentially habitable extrasolar planet so far discovered. Therefore, GL 581 d is used to illustrate a hypothetical detailed spectroscopic characterization of such planets. Methods. Atmospheric profiles for a wide range of possible one-dimensional (1D) radiative-convective model scenarios of GL 581 d were used to calculate high-resolution synthetic emission and transmission spectra. Atmospheres were assumed to be composed of N2, CO2, and H2O. From the spectra, signal-to-noise ratios (SNRs) were calculated for a telescope such as the planned James Webb Space Telescope (JWST). Exposure times were set to be equal to the duration of one transit. Results. The presence of the model atmospheres can be clearly inferred from the calculated synthetic spectra thanks to strong water and carbon-dioxide absorption bands. Surface temperatures can be inferred for model scenarios with optically thin spectral windows. Dense, CO2-rich (potentially habitable) scenarios do not enable us to determine the surface temperatures nor assess habitability. Degeneracies between CO2 concentration and surface pressure complicate the interpretation of the calculated spectra, hence the determination of atmospheric conditions. Still, inferring approximative CO2 concentrations and surface pressures is possible. In practice, detecting atmospheric signals is challenging because the calculated SNR values are well below unity in most of the cases. The SNR for a single transit was only barely larger than unity in some near-IR bands for transmission spectroscopy. Most interestingly, the false-positive detection of biomarker candidates such as methane and ozone might be possible in low resolution spectra because CO2 absorption bands overlap biomarker spectral bands. This can be avoided, however, by observing all main CO2 IR bands instead of concentrating on, e.g., the 4.3 or 15 μm bands only. Furthermore, a masking of ozone signatures by CO2 absorption bands is shown to be possible. Simulations imply that such a false-negative detection of ozone would be possible even for rather high ozone concentrations of up to 10-5.

Titel:Spectroscopic characterization of the atmospheres of potentially habitable planets: GL 581 d as a model case study
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iD
von Paris, P.philip.vonparis@dlr.deNICHT SPEZIFIZIERT
Cabrera, J.juan.cabrera@dlr.deNICHT SPEZIFIZIERT
Hedelt, P.University of Bordeaux, Bordeaux, FranceNICHT SPEZIFIZIERT
Rauer, Heikeheike.rauer@dlr.deNICHT SPEZIFIZIERT
Schreier, Franzfranz.schreier@dlr.deNICHT SPEZIFIZIERT
Stracke, Barbarabarbara.stracke@dlr.deNICHT SPEZIFIZIERT
Erschienen in:Astronomy and Astrophysics
Referierte Publikation:Ja
In Open Access:Nein
In ISI Web of Science:Ja
DOI :10.1051/00046361/201117091
Seitenbereich:Seiten 1-11
HerausgeberInstitution und/oder E-Mail-Adresse der Herausgeber
Verlag:EDP Sciences
Name der Reihe:Planets and Planetary Systems
Stichwörter:Atmospheres, Gliese 581 d, Habitability
HGF - Forschungsbereich:Verkehr und Weltraum (alt)
HGF - Programm:Weltraum (alt)
HGF - Programmthema:W EW - Erforschung des Weltraums
DLR - Schwerpunkt:Weltraum
DLR - Forschungsgebiet:W EW - Erforschung des Weltraums
DLR - Teilgebiet (Projekt, Vorhaben):W - Projekt COROT Beteiligung (alt)
Standort: Berlin-Adlershof , Oberpfaffenhofen
Institute & Einrichtungen:Institut für Methodik der Fernerkundung > Atmosphärenprozessoren
Institut für Planetenforschung > Extrasolare Planeten und Atmosphären
Hinterlegt von: Stock, Joachim Wolfgang
Hinterlegt am:07 Nov 2011 09:06
Letzte Änderung:19 Jul 2016 17:28

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