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Escape and fractionation of volatiles and noble gases from Mars-sized planetary embryos and growing protoplanets.

Odert, Petra and Lammer, Helmut and Erkaev, N. V. and Nikolaou, Athanasia and Lichtenegger, H.I.M. and Johnstone, Colin and Kislyakova, K. G. and Leitzinger, M. and Tosi, Nicola (2018) Escape and fractionation of volatiles and noble gases from Mars-sized planetary embryos and growing protoplanets. Icarus, 307, pp. 327-346. Elsevier. DOI: 10.1016/j.icarus.2017.10.031 ISSN 0019-1035

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Official URL: https://www.sciencedirect.com/science/article/abs/pii/S0019103517301677


Planetary embryos form protoplanets via mutual collisions, which can lead to the development of magma oceans. During their solidification, significant amounts of the mantles’ volatile contents may be outgassed. The resulting H2O/CO2 dominated steam atmospheres may be lost efficiently via hydrodynamic escape due to the low gravity of these Moon- to Mars-sized objects and the high stellar EUV luminosities of the young host stars. Protoplanets forming from such degassed building blocks after nebula dissipation could therefore be drier than previously expected. We model the outgassing and subsequent hydrodynamic escape of steam atmospheres from such embryos. The efficient outflow of H drags along heavier species like O, CO2, and noble gases. The full range of possible EUV evolution tracks of a young solar-mass star is taken into account to investigate the atmospheric escape from Mars-sized planetary embryos at different orbital distances. The estimated envelopes are typically lost within a few to a few tens of Myr. Furthermore, we study the influence on protoplanetary evolution, exemplified by Venus. In particular, we investigate different early evolution scenarios and constrain realistic cases by comparing modeled noble gas isotope ratios with present observations. Isotope ratios of Ne and Ar can be reproduced, starting from solar values, under hydrodynamic escape conditions. Solutions can be found for different solar EUV histories, as well as assumptions about the initial atmosphere, assuming either a pure steam atmosphere or a mixture with accreted hydrogen from the protoplanetary nebula. Our results generally favor an early accretion scenario with a small amount of residual hydrogen from the protoplanetary nebula and a low-activity Sun, because in other cases too much CO2 is lost during evolution, which is inconsistent with Venus’ present atmosphere. Important issues are likely the time at which the initial steam atmosphere is outgassed and/or the amount of CO2 which may still be delivered at later evolutionary stages. A late accretion scenario can only reproduce present isotope ratios for a highly active young Sun, but then unrealistically massive steam atmospheres (few kbar) would be required.

Item URL in elib:https://elib.dlr.de/113937/
Document Type:Article
Title:Escape and fractionation of volatiles and noble gases from Mars-sized planetary embryos and growing protoplanets.
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Odert, Petrapetra.odert (at) oeaw.ac.atUNSPECIFIED
Lammer, Helmutspace research institute, austrian academy of sciences, graz, austria.UNSPECIFIED
Erkaev, N. V.institute for computational modelling, krasnoyarsk, russian federationUNSPECIFIED
Nikolaou, Athanasiaathanasia.nikolaou (at) dlr.deUNSPECIFIED
Lichtenegger, H.I.M.Space Research Institute, Austrian Academy of Sciences, Graz, AustriaUNSPECIFIED
Johnstone, ColinUniversity of Vienna, Department of AstrophysicsUNSPECIFIED
Kislyakova, K. G.University of Vienna, Department of AstrophysicsUNSPECIFIED
Leitzinger, M.insitute for physics, graz, austriaUNSPECIFIED
Tosi, Nicolanicola.tosi (at) dlr.deUNSPECIFIED
Journal or Publication Title:Icarus
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1016/j.icarus.2017.10.031
Page Range:pp. 327-346
Keywords:Atmospheres, evolution, Solar radiation, Planetary formation
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Vorhaben Exploration des Sonnensystems
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Planetary Physics
Deposited By: Nikolaou, Athanasia
Deposited On:10 Nov 2017 12:30
Last Modified:06 Sep 2019 15:26

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