Journal ArticleDOI
Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus
Frank Postberg,Sascha Kempf,Jürgen Schmidt,Nikolai V. Brilliantov,A. Beinsen,Bernd Abel,Udo Buck,Ralf Srama +7 more
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TLDR
The identification of a population of E-ring grains that are rich in sodium salts, which can arise only if the plumes originate from liquid water, and the abundance of various salt components in these particles exhibit a compelling similarity to the predicted composition of a subsurface Enceladus ocean in contact with its rock core.Abstract:
Images from the Cassini spacecraft showed erupting plumes of water vapour and ice particles on Saturn's moon Enceladus, prompting speculation a subsurface ocean might be acting as a source of liquid water. Two groups this week report evidence relevant to the search for this subsurface ocean. The results, at first sight contradictory, leave the ocean a possibility, though still a hypothetical one. Postberg et al. used the Cassini Cosmic Dust Analyser to determine the chemical composition of ice grains in Saturn's E-ring, which consists largely of material from Enceladus. They find a population of E-ring grains rich in sodium salts, which should be possible only if the plumes originate from liquid water. Schneider et al. used Earth-based spectroscopic telescopes to search for sodium emission in the gas plumes erupting from Enceladus and found none. This is inconsistent with a direct supply from a salty ocean and suggests alternative eruption sources such as a deep ocean, a freshwater reservoir or ice. Or if there is a salty reservoir of water, some process not yet determined must be preventing the sodium from escaping into space. Saturn's moon Enceladus emits plumes of water vapour and ice particles from fractures near its south pole, raising the possibility of a subsurface ocean. Minor organic or siliceous components, identified in many ice grains, could be evidence of interaction between Enceladus' rocky core and liquid water; however it has been unclear whether the water is still present today or if it has frozen. Now, the identification of a population of E-ring grains that are rich in sodium salts suggests that the plumes originate from liquid water. Saturn's moon Enceladus emits plumes of water vapour and ice particles from fractures near its south pole1,2,3,4,5, suggesting the possibility of a subsurface ocean5,6,7. These plume particles are the dominant source of Saturn’s E ring7,8. A previous in situ analysis9 of these particles concluded that the minor organic or siliceous components, identified in many ice grains, could be evidence for interaction between Enceladus’ rocky core and liquid water9,10. It was not clear, however, whether the liquid is still present today or whether it has frozen. Here we report the identification of a population of E-ring grains that are rich in sodium salts (∼0.5–2% by mass), which can arise only if the plumes originate from liquid water. The abundance of various salt components in these particles, as well as the inferred basic pH, exhibit a compelling similarity to the predicted composition of a subsurface Enceladus ocean in contact with its rock core11. The plume vapour is expected to be free of atomic sodium. Thus, the absence of sodium from optical spectra12 is in good agreement with our results. In the E ring the upper limit for spectroscopy12 is insufficiently sensitive to detect the concentrations we found.read more
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Journal ArticleDOI
Liquid water on Enceladus from observations of ammonia and 40Ar in the plume
J. H. Waite,W. S. Lewis,Brian Magee,Jonathan I. Lunine,William B. McKinnon,Christopher R. Glein,Olivier Mousis,Olivier Mousis,D. T. Young,Tim Brockwell,Joseph Westlake,M. J. Nguyen,B. D. Teolis,Hasso B. Niemann,Ralph L. McNutt,Mark E. Perry,Wing-Huen Ip +16 more
TL;DR: McKinnon et al. as mentioned in this paper reported that ammonia is present in the plume, along with various organic compounds, deuterium and, very probably, Ar-40, which provides strong evidence for the existence of at least some liquid water, given that temperatures in excess of 180 K have been measured near the fractures from which the jets emanate.
Journal ArticleDOI
A salt-water reservoir as the source of a compositionally stratified plume on Enceladus
TL;DR: Whereas previous Cassini observations were compatible with a variety of plume formation mechanisms, these data eliminate or severely constrain non-liquid models and strongly imply that a salt-water reservoir with a large evaporating surface provides nearly all of the matter in the plume.
Journal ArticleDOI
Cassini finds molecular hydrogen in the Enceladus plume: Evidence for hydrothermal processes.
J. Hunter Waite,Christopher R. Glein,Rebecca Perryman,Ben Teolis,Brian Magee,Greg Miller,J. Grimes,Mark E. Perry,Kelly E. Miller,Alexis Bouquet,Jonathan I. Lunine,Tim Brockwell,Scott Bolton +12 more
TL;DR: The Ion Neutral Mass Spectrometer onboard the Cassini spacecraft is used to detect molecular hydrogen in the plume of escaping material on Enceladus, finding that the most plausible source of this hydrogen is ongoing hydrothermal reactions of rock containing reduced minerals and organic materials.
Journal ArticleDOI
Ongoing hydrothermal activities within Enceladus
Hsiang-Wen Hsu,Frank Postberg,Yasuhito Sekine,Takazo Shibuya,Sascha Kempf,Mihaly Horanyi,Antal Juhász,Nicolas Altobelli,Katsuhiko Suzuki,Yuka Masaki,Tatsu Kuwatani,Shogo Tachibana,Sin Iti Sirono,Georg Moragas-Klostermeyer,Ralf Srama +14 more
TL;DR: Analysis of silicon-rich, nanometre-sized dust particles (so-called stream particles) that stand out from the water-ice-dominated objects characteristic of Saturn indicate ongoing high-temperature (>90 °C) hydrothermal reactions associated with global-scale geothermal activity that quickly transports hydroThermal products from the ocean floor at a depth of at least 40 kilometres up to the plume of Enceladus.
Journal ArticleDOI
Living at the Extremes: Extremophiles and the Limits of Life in a Planetary Context.
Nancy Merino,Heidi S. Aronson,D.P. Bojanova,Jayme Feyhl-Buska,Michael L. Wong,Shu Zhang,Donato Giovannelli +6 more
TL;DR: The current state of knowledge for the biospace in which life operates on Earth is reviewed and discussed in a planetary context, highlighting knowledge gaps and areas of opportunity.
References
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Journal ArticleDOI
Cassini Observes the Active South Pole of Enceladus
Carolyn C. Porco,Paul Helfenstein,Peter C. Thomas,Andrew P. Ingersoll,Jack Wisdom,Robert West,Gerhard Neukum,Tilmann Denk,Roland Wagner,Thomas Roatsch,Susan W. Kieffer,Elizabeth P. Turtle,Alfred S. McEwen,Torrence V. Johnson,Julie A. Rathbun,J. Veverka,Daren Wilson,Jason Perry,Joseph N. Spitale,André Brahic,Joseph A. Burns,Anthony D. DelGenio,Luke Dones,Carl D. Murray,Steven W. Squyres +24 more
TL;DR: Cassini has identified a geologically active province at the south pole of Saturn's moon Enceladus in images acquired by the Imaging Science Subsystem (ISS), this region is circumscribed by a chain of folded ridges and troughs at ∼55°S latitude as mentioned in this paper.
Supporting Online Material for Cassini Observes the Active South Pole of Enceladus
C. C. Porco,P. Helfenstein,P. C. Thomas,Andrew P. Ingersoll,J. Wisdom,R. West,Gerhard Neukum,Tilmann Denk,R. Wagner,T. Roatsch,S. Kieffer,Elizabeth P. Turtle,A. McEwen,T. V. Johnson,Julie A. Rathbun,J. Veverka,Daren Wilson,Jason Perry,J. Spitale,André Brahic,J. Burns,A. D. DelGenio,Luke Dones,C. D. Murray,S. W. Squyres +24 more
TL;DR: The shape of Enceladus suggests a possible intense heating epoch in the past by capture into a 1:4 secondary spin/orbit resonance.
Journal ArticleDOI
Hydration of the alkali ions in the gas phase. Enthalpies and entropies of reactions M+(H2O)n-1 + H2O = M+(H2O)n
I. Dzidic,Paul Kebarle +1 more
Journal ArticleDOI
Cassini ion and neutral mass spectrometer: Enceladus plume composition and structure.
J. Hunter Waite,Michael R. Combi,Wing-Huen Ip,Thomas E. Cravens,Ralph L. McNutt,Wayne Kasprzak,Roger V. Yelle,Janet G. Luhmann,Hasso B. Niemann,David A. Gell,Brian Magee,Greg Fletcher,Jonathan I. Lunine,Wei-Ling Tseng +13 more
TL;DR: INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane.
Journal ArticleDOI
Cassini Encounters Enceladus: Background and the Discovery of a South Polar Hot Spot
John R. Spencer,John C. Pearl,M. E. Segura,F. M. Flasar,A. A. Mamoutkine,Paul N. Romani,Bonnie J. Buratti,Amanda R. Hendrix,Linda Spilker,Rosaly M. C. Lopes +9 more
TL;DR: Cassini's Composite Infrared Spectrometer (CIRS) detected 3 to 7 gigawatts of thermal emission from the south polar troughs at temperatures up to 145 kelvin or higher, making Enceladus only the third known solid planetary body—after Earth and Io—that is sufficiently geologically active for its internal heat to be detected by remote sensing.
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