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| Titel |
Escape and fractionation of volatiles and noble gases: from Mars-sized planetary embryos to growing protoplanets |
| VerfasserIn |
Petra Odert, Helmut Lammer, Nikolai V. Erkaev, Athanasia Nikolaou, Herbert I. M. Lichtenegger, Colin P. Johnstone, Kristina G. Kislyakova, Martin Leitzinger, Nicola Tosi |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250144165
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| Publikation (Nr.) |
 EGU/EGU2017-7959.pdf |
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| Zusammenfassung |
| Planetary embryos form larger planetary objects via collisions. Such Moon- to Mars-sized
bodies can have magma oceans. During the solidification of their magma oceans
planetary embryos may therefore degas significant amounts of their volatiles, forming
H2O/CO2 dominated steam atmospheres. Such atmospheres may escape efficiently
due to the low gravity of these objects and the high EUV emission of the young
host star. Planets forming from such building blocks could therefore be drier than
expected. We model the energy-limited outflow of hydrogen which is able to drag along
heavier species such as O and CO2. We take into account different stellar EUV
evolution tracks to investigate the loss of steam atmospheres from Mars-sized planetary
embryos at different orbital distances. We find that the estimated envelopes are
typically lost within a few to a few tens of Myr. Moreover, we address the influence on
protoplanet evolution using Venus as an example. We investigate different early
evolution scenarios and constrain realistic cases by comparing modeled noble gas
isotope ratios with presently observed ones. We are able to reproduce current ratios
by assuming either a pure steam atmosphere or a mixture with accreted hydrogen
from the protoplanetary nebula. Despite being able to find solutions for different
parameter combinations, our results favor a low-activity Sun with possibly a small
amount of residual H from the protoplanetary nebula. In other cases too much CO2 is
lost during evolution, which is inconsistent with Venus’ present atmosphere. A
critical issue is likely the time at which the initial steam atmosphere is outgassed. |
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