Volume 537, January 2012
|Number of page(s)||6|
|Published online||23 December 2011|
1 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, France
2 Institut d’Astrophysique de Paris, Université Pierre & Marie Curie, CNRS UMR 7095, Paris, France
3 LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, Meudon, France
4 NASA Langley Research Center, Science Directorate, Chemistry and Dynamics Branch, Hampton, Virginia, USA
5 Laboratoire Cassiopée, UMR 6202, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, Nice, France
6 Observatoire de Haute-Provence, CNRS/OAMP, Saint-Michel l’ Observatoire, France
Received: 4 November 2011
Accepted: 1 December 2011
On 5–6 June 2012, Venus will be transiting the Sun for the last time before 2117. This event is an unique opportunity to assess the feasibility of the atmospheric characterisation of Earth-size exoplanets near the habitable zone with the transmission spectroscopy technique and provide an invaluable proxy for the atmosphere of such a planet. In this letter, we provide a theoretical transmission spectrum of the atmosphere of Venus that could be tested with spectroscopic observations during the 2012 transit. This is done using radiative transfer across Venus’ atmosphere, with inputs from in-situ missions such as Venus Express and theoretical models. The transmission spectrum covers a range of 0.1–5 μm and probes the limb between 70 and 150 km in altitude. It is dominated in UV by carbon dioxide absorption producing a broad transit signal of ~20 ppm as seen from Earth, and from 0.2 to 2.7 μm by Mie extinction (~5 ppm at 0.8 μm) caused by droplets of sulfuric acid composing an upper haze layer above the main deck of clouds. These features are not expected for a terrestrial exoplanet and could help discriminating an Earth-like habitable world from a cytherean planet.
Key words: radiative transfer / planets and satellites: atmospheres / astrobiology / planetary systems / scattering / planets and satellites: individual: Venus
Appendix A is available in electronic form at http://www.aanda.org
Full Table A.1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/L2
© ESO, 2012
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