The H2O and O2 exospheres of Ganymede: The result of a complex interaction between the jovian magnetospheric ions and the icy moon

Plainaki, C.; Milillo, A.; Massetti, S.; Mura, A.; Jia, Xianzhe; Orsini, S.; Mangano, V.; Angelis, E. De; Rispoli, Rosanna

doi:10.1016/j.icarus.2014.09.018

Cited by 55 publications

(96 citation statements)

References 76 publications

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“…More recently, Plainaki et al () proposed an innovative method (accurate to an order of magnitude; see Table ) of estimating of expected O 2 production from ion‐irradiated “warm” ice (> ~100 K) at Europa and Ganymede, which they inferred from the temperature‐dependent part of the total sputtering equation of Fama et al (). However, the applicability of the Plainaki et al () method (as updated by Plainaki et al () and Milillo et al ()) to other (possibly colder) icy solar system objects is uncertain because Fama et al () did not elucidate the contribution of O 2 to the sputtered ejecta for ices below ~100 K and did not model the projectile species and energy dependence of the O 2 :H 2 O ratio in the ejecta.…”

Section: Introductionmentioning

confidence: 99%

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

et al. 2017

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O2, H2, and H2O2 radiolysis from water ice is pervasive on icy astrophysical bodies, but the lack of a self‐consistent, quantitative model of the yields of these water products versus irradiation projectile species and energy has been an obstacle to estimating the radiolytic oxidant sources to the surfaces and exospheres of these objects. A major challenge is the wide variation of O2 radiolysis yields between laboratory experiments, ranging over 4 orders of magnitude from 5 × 10−7 to 5 × 10−3 molecules/eV for different particles and energies. We revisit decades of laboratory data to solve this long‐standing puzzle, finding an inverse projectile range dependence in the O2 yields, due to preferential O2 formation from an ~30 Å thick oxygenated surface layer. Highly penetrating projectile ions and electrons with ranges ≳30 Å are therefore less efficient at producing O2 than slow/heavy ions and low‐energy electrons (≲ 400 eV) which deposit most energy near the surface. Unlike O2, the H2O2 yields from penetrating projectiles fall within a comparatively narrow range of (0.1–6) × 10−3 molecules/eV and do not depend on range, suggesting that H2O2 forms deep in the ice uniformly along the projectile track, e.g., by reactions of OH radicals. We develop an analytical model for O2, H2, and H2O2 yields from pure water ice for electrons and singly charged ions of any mass and energy and apply the model to estimate possible O2 source rates on several icy satellites. The yields are upper limits for icy bodies on which surface impurities may be present.

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Section: Introductionmentioning

confidence: 99%

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

et al. 2017

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“…the breaking and topological rearrangement of magnetic field lines in a plasma, resulting in the conversion of magnetic field energy to plasma kinetic and thermal energy) could lead to some sputtering of surface material at low latitudes from recently trapped particles; in those regions, however, such a process is expected to have lower rates than in the polar caps. Recent simulations by Plainaki et al (2015) of Ganymede's sputter-induced water exosphere support this scenario. In contrast to Ganymede, the entire surface of Europa is bombarded by Jovian plasma (maximum precipitating flux is at the trailing hemisphere apex), suggesting that sputter-induced redistribution of water molecules is a viable means of brightening the satellite's surface.…”

Section: Space Weather Interactions In the Solar Systemmentioning

confidence: 91%

“…The moon exosphere source-loss balance, consequently, depends on a complex pattern of planetary space weather conditions. Plainaki et al (2015) used previously published estimates of plasma parameters (McNutt et al 1981;Scudder et al 1981;Gurnett et al 1996;Eviatar et al 2001;Kivelson et al 2004) to calculate the rates of the most important plasma-moon interactions leading to the loss of Ganymede's exosphere. They found that the loss rate for H 2 O in the polar caps is due to its charge exchange with ionospheric O 2 + whereas in the closed magnetic field lines region, the H 2 O loss rate is lower by almost one order of magnitude and is mainly due to charge exchange between ionospheric O + and H 2 O.…”

Section: Space Weather At the Galilean Moonsmentioning

confidence: 99%

“…Smyth & Marconi (2006) developed a 2D axisymmetric kinetic model considering ion-neutral collisions and assuming that the source rates for the various species (H 2 O, O 2 , H 2 etc.) were determined by partitioning the O 2 source rate derived by the UV (Plainaki et al 2012(Plainaki et al , 2013, accounting for the release-yield revisions (see Milillo et al 2015;Plainaki et al 2015 …”

Section: à2mentioning

confidence: 99%

“…Therefore, the fastest MHD waves can propagate upstream of a moon whereas the perturbations that slow and divert the flow develop gradually and shocks do not form, except possibly at Callisto . Moons are significant plasma sources for the outer planets' magnetospheres providing material through volcanism, plumes or particles released directly from their surfaces due to sputtering, radiolysis and sublimation Plainaki et al 2012Plainaki et al , 2015. Io and Europa are believed to be major plasma sources for Jupiter's magnetosphere, similarly to Enceladus for Saturn's and Triton for Neptune's magnetospheres (see Table 3).…”

Section: Plasma and Magnetic Fieldsmentioning

confidence: 99%

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Planetary space weather: scientific aspects and future perspectives

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In this paper, we review the scientific aspects of planetary space weather at different regions of our Solar System, performing a comparative planetology analysis that includes a direct reference to the circum-terrestrial case. Through an interdisciplinary analysis of existing results based both on observational data and theoretical models, we review the nature of the interactions between the environment of a Solar System body other than the Earth and the impinging plasma/radiation, and we offer some considerations related to the planning of future space observations. We highlight the importance of such comparative studies for data interpretations in the context of future space missions (e.g. ESA JUICE; ESA/JAXA BEPI COLOMBO). Moreover, we discuss how the study of planetary space weather can provide feedback for better understanding the traditional circumterrestrial space weather. Finally, a strategy for future global investigations related to this thematic is proposed.

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The search for a subsurface ocean in Ganymede with Hubble Space Telescope observations of its auroral ovals

et al. 2015

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We present a new approach to search for a subsurface ocean within Ganymede through observations and modeling of the dynamics of its auroral ovals. The locations of the auroral ovals oscillate due to Jupiter's time-varying magnetospheric field seen in the rest frame of Ganymede. If an electrically conductive ocean is present, the external time-varying magnetic field is reduced due to induction within the ocean and the oscillation amplitude of the ovals decreases. Hubble Space Telescope (HST) observations show that the locations of the ovals oscillate on average by 2.0• ± 1.3 • . Our model calculations predict a significantly stronger oscillation by 5.8Because the ocean and the no-ocean hypotheses cannot be separated by simple visual inspection of individual HST images, we apply a statistical analysis including a Monte Carlo test to also address the uncertainty caused by the patchiness of observed emissions. The observations require a minimum electrical conductivity of 0.09 S/m for an ocean assumed to be located between 150 km and 250 km depth or alternatively a maximum depth of the top of the ocean at 330 km. Our analysis implies that Ganymede's dynamo possesses an outstandingly low quadrupole-to-dipole moment ratio. The new technique applied here is suited to probe the interior of other planetary bodies by monitoring their auroral response to time-varying magnetic fields.

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The H2O and O2 exospheres of Ganymede: The result of a complex interaction between the jovian magnetospheric ions and the icy moon

Cited by 55 publications

References 76 publications

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Planetary space weather: scientific aspects and future perspectives

The search for a subsurface ocean in Ganymede with Hubble Space Telescope observations of its auroral ovals

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The H2O and O2 exospheres of Ganymede: The result of a complex interaction between the jovian magnetospheric ions and the icy moon

Cited by 55 publications

References 76 publications

Water Ice Radiolytic O2, H2, and H2O2 Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Water Ice Radiolytic O2, H2, and H2O2 Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Planetary space weather: scientific aspects and future perspectives

The search for a subsurface ocean in Ganymede with Hubble Space Telescope observations of its auroral ovals

Contact Info

Product

Resources

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Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies