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J/A+A/523/A57       The Earth as a transiting planet       (Vidal-Madjar+, 2010)

The Earth as an extrasolar transiting planet: Earth's atmosphere composition and thickness revealed by Lunar eclipse observations. Vidal-Madjar A., Arnold L., Ehrenreich D., Ferlet R., Lecavelier des Etangs A., Bouchy F., Segransan D., Boisse I., Hebrard G., Moutou C., Desert J.-M., Sing D.K., Cabanac R., Nitschelm C., Bonfils X., Delfosse X., Desort M., Diaz R.F., Eggenberger A., Forveille T., Lagrange A.-M., Lovis C., Pepe F., Perrier C., Pont F., Santos N.C., Udry S. <Astron. Astrophys. 523, A57 (2010)> =2010A&A...523A..57V
ADC_Keywords: Earth ; Spectroscopy Keywords: eclipses - Earth - planets and satellites: atmospheres - astrobiology - techniques: spectroscopic - methods: observational Abstract: An important goal within the quest for detecting an Earth-like extrasolar planet, will be to identify atmospheric gaseous bio-signatures. Aims. Observations of the light transmitted through the Earth's atmosphere, as for an extrasolar planet, will be the first important step for future comparisons. We have completed observations of the Earth during a lunar eclipse, a unique situation similar to that of a transiting planet. We aim at showing what species could be detected in its atmosphere at optical wavelengths, where a lot of photons are available in the masked stellar light. We present observations of the 2008 August 16 Moon eclipse performed with the SOPHIE spectrograph at the Observatoire de Haute- Provence (France). Locating the spectrograph's fibers in the penumbra of the eclipse, the Moon irradiance is then a mix of direct, unabsorbed Sun light and solar light that has passed through the Earth's atmosphere. This mixture essentially reproduces what is recorded during the transit of an extrasolar planet. We report here the clear detection of several Earth atmospheric compounds in the transmission spectra, such as ozone, molecular oxygen, and neutral sodium as well as molecular nitrogen and oxygen through the Rayleigh signature. Moreover, we present a method that allows us to derive the thickness of the atmosphere versus the wavelength for penumbra eclipse observations. We quantitatively evaluate the altitude at which the atmosphere becomes transparent for important species like molecular oxygen and ozone, two species thought to be tightly linked to the presence of life. The molecular detections presented here are an encouraging first attempt, necessary to better prepare for the future of extremely-large telescopes and transiting Earth-like planets. Instruments like SOPHIE will be mandatory when characterizing the atmospheres of transiting Earth-like planets from the ground and searching for bio-marker signatures. Description: Spectral distribution of the effective height h of the Earth atmosphere as observed with the SOPHIE instrument on the 193cm telescope at the Observatoire de Haute-Provence during the 16 August 2008 Lunar eclipse. These evaluations are made at about 2Å and 0.02Å spectral resolution. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file fig9o3.dat 34 1471 Ozone, 2Å resolution fig10na.dat 34 1200 NaI, 0.02Å resolution fig11o2b.dat 34 8000 O2 B(0-1), 6880Å, 0.02Å resolution fig12o2g.dat 34 6000 O2 γ(2-0), 6280Å, 0.02Å resolution
Byte-by-byte Description of file: fig*
Bytes Format Units Label Explanations
7- 15 F9.4 0.1nm lambda Wavelength 24- 34 E11.5 km h Effective altitude (1)
Note (1): h,is the effective altitude extracted from the observations as plotted in the corresponding figures in thick solid line. The E11.5 format is in double precision as e.g. 2.5853e+001.
Acknowledgements: Alfred Vidal-Madjar, alf(at)iap.fr
(End) Patricia Vannier [CDS] 06-Jul-2010
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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