Gas Trapping in Ice and Its Release upon Warming

Bar‐Nun, A.; Laufer, D.; Rebolledo, Oscar R.; Malyk, S.; Reisler, H.; Wittig, C.

doi:10.1007/978-1-4614-3076-6_14

Cited by 15 publications

(43 citation statements)

References 21 publications

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“…This is the case even allowing for the thermal delays in emission suggested by laboratory measurements (Teolis et al 2005;). However, O 2 trapped in an ice regolith can in principle be released thermally, as discussed frequently (e.g., Bar-Nun et al 2013;Laufer et al 2017), and as also seen experimentally on warming an irradiated ice sample (Teolis et al 2005). Therefore, a regolith permeated with O 2 that can be desorbed by the solar flux, could in principal dominate the O 2 sputter source.…”

Section: Simulationsmentioning

confidence: 77%

The Origin and Fate of O 2 $\mbox{O}_{2}$ in Europa’s Ice: An Atmospheric Perspective

et al. 2019

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The early prediction and subsequent detection of an O 2 atmosphere on Europa, coupled with the discovery that Europa has an ocean under its ice mantle, has made this moon a prime astrobiologic target, soon to be visited by the JUICE and Europa Clipper spacecraft. In spite of the considerable number of observational, modeling, and laboratory efforts, understanding the physics leading to the observed morphology of Europa's nearsurface O 2 atmosphere has been problematic. This is the case as the observed emissions depend on the local incident plasma ion flux, the local temperature and composition of the regolith, as well as on the near-surface electron temperature and density. Here we rely heavily on earlier reviews briefly summarizing the observational, laboratory and simulation efforts. Although it is agreed that radiolysis of the surface ice by the incident Jovian plasma is the ultimate source of observed O 2 , a recent, simple model of thermal desorption from a regolith permeated with O 2 has changed the usual paradigm. In that model, the observed orbital dependence of the local source of the near-surface O 2 atmosphere is suggested to be due to the release of O 2 likely trapped on the ice grains at dangling bonds by the solar flux with a smaller contribution due to direct sputtering. This assumes that Europa's icy regolith is permeated with trapped O 2 , which could also affect our understanding of the suggestion that the radiolytic products in Europa's regolith might be a source of oxidants for its underground ocean.

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Section: Simulationsmentioning

confidence: 77%

The Origin and Fate of O 2 $\mbox{O}_{2}$ in Europa’s Ice: An Atmospheric Perspective

et al. 2019

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“…On the other hand, radiolysis and photolysis of water ice as a formation scenario for O 2 leads to the formation of byproducts such as H 2 O 2 , HO 2 , and O 3 in amounts much larger compared to that observed at 67P/C-G. -The presence of S 2 , which has a very short lifetime when exposed to UV photons, requires preservation in the ices originating in the presolar cloud (Calmonte et al 2016;Mousis et al 2017b). However, the degree to which this also applies to other volatiles, apart from H 2 O, O 2 , and S 2 ( Bar-Nun et al 2012;Greenberg et al 2017), or whether they were evaporated and then recondensed from the gas phase in the protosolar nebula (Mousis et al 2018b) is still debated. It seems clear, however, that a single ice phase is not able to reproduce the observed relative abundances, and/or the material in the comet was subject to evolutionary processes, such as temperature-dependent fractionation, occurring on different time scales of the comet's journey through the solar system.…”

Section: Discussionmentioning

confidence: 97%

“…However, the degree to which this also applies to other volatiles, apart from H 2 O, O 2 , and S 2 (Bar-Nun et al. 2012 ; Greenberg et al. 2017 ), or whether they were evaporated and then recondensed from the gas phase in the protosolar nebula (Mousis et al.…”

Section: Discussionmentioning

confidence: 99%

“…In the case of amorphous ice, such a ratio would move the formation temperature of 67P/C-G towards even lower values, possibly into the low 20 K range (Bar-Nun et al 2007). However, such a scenario would also lead to an even higher Ar/CO ratio, which is not observed and is at odds with the absence of the noble gas neon in the coma of comet 67P/C-G ( Bar-Nun et al 2012;. What remains to be understood, however, is the impact of other ices aside from H 2 O.…”

Section: On the Ice Phase And Formation Temperature Of 67p/c-gmentioning

confidence: 99%

“…However, such a scenario would also lead to an even higher Ar/CO ratio, which is not observed and is at odds with the absence of the noble gas neon in the coma of comet 67P/C-G (Bar-Nun et al. 2012 ; Rubin et al. 2018 ).…”

Section: Conditions At the Location Of Formation Of Cometsmentioning

confidence: 99%

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On the Origin and Evolution of the Material in 67P/Churyumov-Gerasimenko

et al. 2020

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Primitive objects like comets hold important information on the material that formed our solar system. Several comets have been visited by spacecraft and many more have been observed through Earth-and space-based telescopes. Still our understanding remains limited. Molecular abundances in comets have been shown to be similar to interstellar ices and thus indicate that common processes and conditions were involved in their formation. The samples returned by the Stardust mission to comet Wild 2 showed that the bulk refractory material was processed by high temperatures in the vicinity of the early sun. The recent Rosetta mission acquired a wealth of new data on the composition of comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) and complemented earlier observations of other comets. The isotopic, elemental, and molecular abundances of the volatile, semivolatile, and refractory phases brought many new insights into the origin and processing of the incorporated material. The emerging picture after Rosetta is that at least part of the volatile material was formed before the solar system and that cometary nuclei agglomerated over a wide range of heliocentric distances, different from where they are found today. Deviations from bulk solar system abundances indicate that the material was not fully homogenized at the location of comet formation, despite the radial mixing implied by the Stardust results. Post-formation evolution of the material might play an important role, which further

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