J/A+A/537/L2 Transmission spectrum of Venus (Ehrenreich+, 2012)
Transmission spectrum of Venus as a transiting exoplanet.
Ehrenreich D., Vidal-Madjar A., Widemann T., Grono G., Tanga P.,
Barthelemy M., Lilensten J., Lecavelier des Etangs A., Arnold L.
<Astron. Astrophys. 537, L2 (2012)>
=2012A&A...537L...2E 2012A&A...537L...2E
ADC_Keywords: Planets ; Spectroscopy
Keywords: radiative transfer - planets and satellites: atmospheres -
astrobiology - planetary systems - scattering -
planets and satellites: individual: Venus
Abstract:
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 0.1-5m and probes the limb between 70 and
150km in altitude. It is dominated in UV by carbon dioxide absorption
producing a broad transit signal of ∼20ppm as seen from Earth, and
from 0.2 to 2.7m by Mie extinction (∼5ppm at 0.8m) 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.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 80 3740 Transit spectra of Venus from Figs. 2b
(absorption) and 2c (effective height)
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 nm lambda [100/3840] Wavelength (range 0.1--3.8µm)
7- 19 F13.10 10-6 Abs0 Absorption (no haze) (in ppm) (1)
21- 33 F13.10 10-6 Abs1 Absorption (mode-1 haze) (in ppm) (1)
35- 47 F13.10 10-6 Abs2 Absorption (mode-1+2 haze) (in ppm) (1)
49- 58 F10.6 km h0 Effective height (no haze) (1)
60- 69 F10.6 km h1 Effective height (model-1 haze) (1)
71- 80 F10.6 km h2 Effective height (model-2 haze) (1)
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Note (1): the models 1 and 2 correspond to a haze of H2SO4 droplets
following a log-normal distribution with size parameters of
(rg=0.2µm, σg=0.2) and (rg=0.6µm, σg=1.5)
respectively.
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Acknowledgements:
David Ehrenreich, david.ehrenreich(at)obs.ujf-grenoble.fr
(End) Patricia Vannier [CDS] 05-Dec-2011