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| Titel |
Aeronomical evidence for higher CO2 levels during Earth's Hadean epoch |
| VerfasserIn |
Herbert I. M. Lichtenegger, Helmut Lammer, Jean-Mathias Grießmeier, Yuri Kulikov, Philip von Paris, Heike Rauer |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040167
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| Zusammenfassung |
| According to recent simulations of the Earth’s thermosphere, the exospheric temperature is
not expected to rise above 7000–8000 K even under extreme solar EUV conditions
anticipated for the early Earth. Rather, when the solar EUV flux exceeds some critical value,
the escaping flow of the bulk upper thermosphere starts cooling it due to adiabatic expansion,
which results in a decrease of the exobase temperature. Under these extreme conditions, the
exobase may expand above the magnetopause and the magnetosphere had not been able
to protect the upper atmosphere against strong non-thermal erosion by the solar
wind. It is shown that a nitrogen-rich terrestrial atmosphere with a present-day
composition would have been removed within a few million years during the extreme
EUV and solar wind conditions that are expected to have prevailed before the late
heavy bombardment period ~ 3.8 Ga ago. Our results suggest that a CO2 amount in
the early nitrogen-rich terrestrial atmosphere of about two orders of magnitude
higher than the present-time level could have confined the upper atmosphere within
the shielding magnetosphere and thus might have had protected it from complete
destruction. |
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