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| Titel |
Determination of the exospheric temperature of CO2 and O2 rich exoplanets |
| VerfasserIn |
Guillaume Gronoff, Romain Maggiolo, Christopher J. Mertens, Cyril Simon Wedlund, David Bernard, Mathieu Barthelemy |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083219
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| Zusammenfassung |
| The discovery of Earth-sized exoplanets orbiting in, or near, the so-called habitable zone
leads to questions concerning the presence, the characteristics, and the evolution of their
atmospheres. For giant exoplanets, the characterization of their atmosphere has already
started, with major discoveries such as the observation of evaporation of hot-Jupiter
atmospheres.
One technique to better understand these processes would be to determine the
exospheric temperature of these atmospheres since it is the main parameter for
atmospheric escape (both thermal and non-thermal). The exospheric temperature is highly
dependent on the composition: CO2-rich planets, Venus and Mars, are known to have a
small exospheric temperature (200 - 300 K), compared to other planets like Earth
(800 - 1600 K) or Jupiter (700 - 1000 K). The determination of the exospheric
temperature on exoplanets is therefore an important step to determine the stability and the
evolution of their atmospheres, and to help understand how our own solar system
evolved.
To reach this goal, measurements have to be done in the UV, because the emission/absorption
of lower layers of the planet may mask the infrared features of the upper atmosphere.
Currently, several UV absorption techniques are proposed to determine the atmospheric
composition, but rely on several hypotheses concerning the composition of the
planetary atmosphere. The CO2 and O2 molecules have an uncommon feature in the
150-200 nm region: their UV absorption is strongly temperature (in addition to
wavelength) dependent. In this work, we present the theoretical calculation of the UV
absorption by several planetary atmospheres rich in O2 or CO2, taking into account the
temperature dependence, and we show that this feature allows to decorrelate the scale
height of the thermosphere from the temperature of its neutral species. It means that
it is possible to determine the exospheric temperature and to check whether the
atmosphere is in hydrostatic equilibrium or in hydrodynamical escape. Finally, we
stress the necessity for adequate instrumentation in order to test this technique. |
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