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

Paris, Philip von; Cabrera, J.; Godolt, M.; Grenfell, John Lee; Hedelt, Pascal; Rauer, H.; Schreier, Franz; Stracke, Barbara

doi:10.1051/0004-6361/201117091

Cited by 26 publications

(14 citation statements)

References 72 publications

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“…A26, page 2 of 13 where p is the atmospheric pressure and n m the number density of molecule m. In high-resolution line-by-line models the absorption cross section k m is given by the superposition of many lines, Grenfell et al (2011);Rauer et al (2011) andvon Paris et al (2011).…”

Section: Radiative Transfermentioning

confidence: 99%

Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M stars

Vasquez

Schreier

García

et al. 2012

A&A

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Context. The atmosphere of Earth-like extrasolar planets orbiting different types of stars is influenced by the spectral dependence of the incoming stellar radiation. The changes in structure and composition affect atmospheric radiation, hence the spectral appearance of these exoplanets. Aims. We provide a thorough investigation of infrared radiative transfer in cloud-free exoplanets atmospheres by not only analyzing the planetary spectral appearance but also discussing the radiative processes behind the spectral features in detail and identifying the regions in the atmosphere that contribute most at a given wavelength. Methods. Using cloud-free scenarios provided by a one-dimensional radiative-convective steady-state atmospheric model, we computed high-resolution infrared transmission and emission spectra, as well as weighting functions for exoplanets located within the habitable zone of F, G, K, and M stars by means of a line-by-line molecular absorption model and a Schwarzschild solver for the radiative transfer. The monochromatic spectra were convolved with appropriate spectral response functions to study the effects of finite instrument resolution. Results. Spectra of the exoplanets of F, G, K, and M stars were analyzed in the 4.5 µm N 2 O band, the 4.3 µm and 15 µm CO 2 bands, the 7.7 µm CH 4 band, the 6.3 µm H 2 O band, and the 9.6 µm O 3 band. Differences in the state of the atmosphere of the exoplanets clearly show up in the thermal infrared spectra; absorption signatures known from Earth can be transformed to emission features (and vice versa). Weighting functions show that radiation in the absorption bands of the uniformly mixed gases (CO 2 , CH 4 , N 2 O) and (to some extent) ozone comes from the stratosphere and upper troposphere, and also indicate that changes in the atmospheres can shift sources of thermal radiation to lower or higher altitudes. Molecular absorption and/or emission features can be identified in the high-resolution spectra of all planets and in most reduced resolution spectra. Conclusions. Insight into radiative transfer processes is essential for analyzing exoplanet spectral observations; for instance, understanding the impact of the temperature profile (nb. non-existence of an inversion) on the CO 2 bands facilitates their interpretation and can help avoid false positive or negative estimates of O 3 . The detailed analysis of the radiation source and sink regions could even help give an indication about the feasibility of identifying molecular signatures in cloud-covered planets, i.e. radiation mainly coming from the upper atmosphere is less likely to be hidden by clouds. Infrared radiative transfer and biomarker detectability in cloud-covered exoplanets will be presented in a companion paper.

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Section: Radiative Transfermentioning

confidence: 99%

Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M stars

Vasquez

Schreier

García

et al. 2012

A&A

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“…The importance of the planetary system around the 0.31 M , M3V star GJ581 is in this context: According to Von Paris et al (2011) and Kaltenegger et al (2011), GJ581 d is a potentially habitable exoplanet. Besides, a fifth putative planet, GJ581 g, could exist in the central part of the habitable zone.…”

Section: Introductionmentioning

confidence: 99%

A new analysis of the GJ581 extrasolar planetary system

Santos

Silva

Ferraz-Mello

et al. 2012

Celest Mech Dyn Astr

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We have done a new analysis of the available observations for the GJ581 exoplanetary system. Today this system is controversial due to choices that can be done in the orbital determination. The main ones are the ocurrence of aliases and the additional bodies - the planets f and g - announced in Vogt et al. 2010. Any dynamical study of exoplanets requires the good knowledge of the orbital elements and the investigations involving the planet g are particularly interesting, since this body would lie in the Habitable Zone (HZ) of the star GJ581. This region,for this system, is very attractive of the dynamical point of view due to several resonances of two and three bodies present there. In this work, we investigate the conditions under which the planet g may exist. We stress the fact that the planet g is intimately related with the orbital elements of the planet d; more precisely, we conclude that it is not possible to disconnect its existence from the determination of the eccentricity of the planet d. Concerning the planet f, we have found one solution with period $\approx 450$ days, but we are judicious about any affirmation concernig this body because its signal is in the threshold of detection and the high period is in a spectral region where the ocorruence of aliases is very common. Besides, we outline some dynamical features of the habitable zone with the dynamical map and point out the role played by some resonances laying there.Comment: 12 pages, 9 figure

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“…Oxygen or ozone may be quickly consumed by chemical reactions, preventing it from reaching detectable levels (Schindler & Kasting 2000;Selsis et al 2002). Also, non-detection can result from masking by a wide CO 2 absorption (Selsis et al 2002;von Paris et al 2011). Here, we look into an abiotic process (namely GCRs) which can destroy the signature of biosignature molecules.…”

Section: Spectral Signature Of Biosignature Moleculesmentioning

confidence: 99%

Galactic cosmic rays on extrasolar Earth-like planets

Grießmeier

Vakili

Stadelmann

et al. 2016

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Context. Theoretical arguments indicate that close-in terrestial exoplanets may have weak magnetic fields. As described in the companion article (Paper I), a weak magnetic field results in a high flux of galactic cosmic rays to the top of the planetary atmosphere. Aims. We investigate effects that may result from a high flux of galactic cosmic rays both throughout the atmosphere and at the planetary surface. Methods. Using an air shower approach, we calculate how the atmospheric chemistry and temperature change under the influence of galactic cosmic rays for Earth-like (N 2 -O 2 dominated) atmospheres. We evaluate the production and destruction rate of atmospheric biosignature molecules. We derive planetary emission and transmission spectra to study the influence of galactic cosmic rays on biosignature detectability. We then calculate the resulting surface UV flux, the surface particle flux, and the associated equivalent biological dose rates. Results. We find that up to 20% of stratospheric ozone is destroyed by cosmic-ray protons. The effect on the planetary spectra, however, is negligible. The reduction of the planetary ozone layer leads to an increase in the weighted surface UV flux by two orders of magnitude under stellar UV flare conditions. The resulting biological effective dose rate is, however, too low to strongly affect surface life. We also examine the surface particle flux: For a planet with a terrestrial atmosphere (with a surface pressure of 1033 hPa), a reduction of the magnetic shielding efficiency can increase the biological radiation dose rate by a factor of two, which is non-critical for biological systems. For a planet with a weaker atmosphere (with a surface pressure of 97.8 hPa), the planetary magnetic field has a much stronger influence on the biological radiation dose, changing it by up to two orders of magnitude. Conclusions. For a planet with an Earth-like atmospheric pressure, weak or absent magnetospheric shielding against galactic cosmic rays has little effect on the planet. It has a modest effect on atmospheric ozone, a weak effect on the atmospheric spectra, and a noncritical effect on biological dose rates. For planets with a thin atmosphere, however, magnetospheric shielding controls the surface radiation dose and can prevent it from increasing to several hundred times the background level.

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

Cited by 26 publications

References 72 publications

Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M stars

Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M stars

A new analysis of the GJ581 extrasolar planetary system

Galactic cosmic rays on extrasolar Earth-like planets

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