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Ongoing hydrothermal activities within Enceladus



Detection of sodium-salt-rich ice grains emitted from the plume of the Saturnian moon Enceladus suggests that the grains formed as frozen droplets from a liquid water reservoir that is, or has been, in contact with rock1,2. Gravitational field measurements suggest a regional south polar subsurface ocean of about 10 kilometres thickness located beneath an ice crust 30 to 40 kilometres thick3. These findings imply rock–water interactions in regions surrounding the core of Enceladus. The resulting chemical ‘footprints’ are expected to be preserved in the liquid and subsequently transported upwards to the near-surface plume sources, where they eventually would be ejected and could be measured by a spacecraft4. Here we report an analysis of silicon-rich, nanometre-sized dust particles5,6,7,8 (so-called stream particles) that stand out from the water-ice-dominated objects characteristic of Saturn. We interpret these grains as nanometre-sized SiO2 (silica) particles, initially embedded in icy grains emitted from Enceladus’ subsurface waters and released by sputter erosion in Saturn’s E ring. The composition and the limited size range (2 to 8 nanometres in radius) of stream particles 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.

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Figure 1: Identifying particle constituents.
Figure 2: Minimum temperatures for formation of silica nanoparticles.
Figure 3: A schematic of Enceladus’ interior.
Figure 4: Concentration of silica nanoparticles in E-ring grains.


  1. Postberg, F. et al. Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus. Nature 459, 1098–1101 (2009)

    CAS  Article  ADS  PubMed  Google Scholar 

  2. Postberg, F., Schmidt, J., Hillier, J., Kempf, S. & Srama, R. A salt-water reservoir as the source of a compositionally stratified plume on Enceladus. Nature 474, 620–622 (2011)

    CAS  Article  ADS  PubMed  Google Scholar 

  3. Iess, L. et al. The gravity field and interior structure of Enceladus. Science 344, 78–80 (2014)

    CAS  Article  ADS  PubMed  Google Scholar 

  4. Hillier, J. K. et al. The composition of Saturn’s E ring. Mon. Not. R. Astron. Soc. 377, 1588–1596 (2007)

    CAS  Article  ADS  Google Scholar 

  5. Kempf, S. et al. High-velocity streams of dust originating from Saturn. Nature 433, 289–291 (2005)

    CAS  Article  ADS  PubMed  Google Scholar 

  6. Kempf, S. et al. Composition of Saturnian stream particles. Science 307, 1274–1276 (2005)

    CAS  Article  ADS  PubMed  Google Scholar 

  7. Hsu, H.-W. et al. Stream particles as the probe of the dust-plasma-magnetosphere interaction at Saturn. J. Geophys. Res. 116, A09215 (2011)

    ADS  Google Scholar 

  8. Hsu, H.-W., Krüger, H. & Postberg, F. in Nanodust in the Solar System: Discoveries and Interpretations (eds Mann, I., Meyer-Vernet, N. & Czechowski, A. ) 77–117 (Springer Astrophysics and Space Science Library, Vol. 385, 2012)

    Book  Google Scholar 

  9. Srama, R. et al. The Cassini cosmic dust analyzer. Space Sci. Rev. 114, 465–518 (2004)

    CAS  Article  ADS  Google Scholar 

  10. Postberg, F. et al. Discriminating contamination from particle components in spectra of Cassini’s dust detector CDA. Planet. Space Sci. 57, 1359–1374 (2009)

    CAS  Article  ADS  Google Scholar 

  11. Ming, T. et al. Meteoritic silicon carbide and its stellar sources — implications for galactic chemical evolution. Nature 339, 351–354 (1989)

    CAS  Article  ADS  Google Scholar 

  12. Iler, R. K. The Chemistry of Silica (Wiley & Sons, 1979)

    Google Scholar 

  13. Allen, L. H. & Matijević, E. Stability of colloidal silica, I. Effect of simple electrolytes. J. Colloid Interface Sci. 31, 287–296 (1969)

    CAS  Article  ADS  Google Scholar 

  14. Icopini, G. A., Brantley, S. L. & Heaney, P. J. Kinetics of silica oligomerization and nanocolloid formation as a function of pH and ionic strength at 25°C. Geochim. Cosmochim. Acta 69, 293–303 (2005)

    CAS  Article  ADS  Google Scholar 

  15. Conrad, C. F. et al. Modeling the kinetics of silica nanocolloid formation and precipitation in geologically relevant aqueous solutions. Geochim. Cosmochim. Acta 71, 531–542 (2007)

    CAS  Article  ADS  Google Scholar 

  16. Tobler, D. J., Shaw, S. & Benning, L. G. Quantification of initial steps of nucleation and growth of silica nanoparticles: an in-situ SAXS and DLS study. Geochim. Cosmochim. Acta 73, 5377–5393 (2009)

    CAS  Article  ADS  Google Scholar 

  17. Tobler, D. J. & Benning, L. G. In situ and time resolved nucleation and growth of silica nanoparticles forming under simulated geothermal conditions. Geochim. Cosmochim. Acta 114, 156–168 (2013)

    Article  ADS  Google Scholar 

  18. Herzig, P. M. et al. Hydrothermal silica chimney fields in the Galapagos Spreading Center at 86° W. Earth Planet. Sci. Lett. 89, 261–272 (1988)

    CAS  Article  ADS  Google Scholar 

  19. Channing, A. & Butler, I. B. Cryogenic opal-A deposition from Yellowstone hot springs. Earth Planet. Sci. Lett. 257, 121–131 (2007)

    CAS  Article  ADS  Google Scholar 

  20. Zolotov, M. Y. Aqueous fluid composition in CI chondritic materials: chemical equilibrium assessments in closed systems. Icarus 220, 713–729 (2012)

    CAS  Article  ADS  Google Scholar 

  21. Sirono, S. Differentiation of silicates from H2O ice in an icy body induced by ripening. Earth Planets Space 65, 1563–1568 (2013)

    CAS  Article  ADS  Google Scholar 

  22. Matson, D. L., Castillo-Rogez, J. C., Davies, A. G. & Johnson, T. V. Enceladus: a hypothesis for bringing both heat and chemicals to the surface. Icarus 221, 53–62 (2012)

    CAS  Article  ADS  Google Scholar 

  23. Schmidt, J., Brilliantov, N., Spahn, F. & Kempf, S. Slow dust in Enceladus’ plume from condensation and wall collisions in tiger stripe fractures. Nature 451, 685–688 (2008)

    CAS  Article  ADS  PubMed  Google Scholar 

  24. Kempf, S. et al. The E ring in the vicinity of Enceladus. I. Spatial distribution and properties of the ring particles. Icarus 193, 420–437 (2008)

    Article  ADS  Google Scholar 

  25. Malamud, U. & Prialnik, D. Modeling serpentinization: applied to the early evolution of Enceladus and Mimas. Icarus 225, 763–774 (2013)

    CAS  Article  ADS  Google Scholar 

  26. Tielens, A. G. G. M. et al. The physics of grain-grain collisions and gas-grain sputtering in interstellar shocks. Astrophys. J. 431, 321–340 (1994)

    CAS  Article  ADS  Google Scholar 

  27. Spahn, F. et al. Cassini dust measurements at Enceladus and implications for the origin of the E ring. Science 311, 1416–1418 (2006)

    CAS  Article  ADS  Google Scholar 

  28. Horányi, M., Burns, J. & Hamilton, D. G. Dynamics of Saturn’s E ring particles. Icarus 97, 248–259 (1992)

    Article  ADS  Google Scholar 

  29. Horányi, M., Juhász, A. & Morfill, G. E. Large-scale structure of Saturn’s E-ring. Geophys. Res. Lett. 35, L04203 (2008)

    Article  ADS  CAS  Google Scholar 

  30. Horányi, M. Dust streams from Jupiter and Saturn. Phys. Plasmas 7, 3847–3850 (2000)

    Article  ADS  Google Scholar 

  31. Burton, M. E., Dougherty, M. K. & Russell, C. T. Saturn’s internal planetary magnetic field. Geophys. Res. Lett. 37, L24105 (2010)

    Article  ADS  Google Scholar 

  32. Jurac, S., Johnson, R. E. & Richardson, J. D. Saturn’s E ring and production of neutral torus. Icarus 149, 384–396 (2001)

    CAS  Article  ADS  Google Scholar 

  33. Johnson, R. E. et al. Sputtering of ice grains and icy satellites in Saturn’s inner magnetosphere. Planet. Space Sci. 56, 1238–1243 (2008)

    CAS  Article  ADS  Google Scholar 

  34. Shi, M. et al. Sputtering of water ice surfaces and the production of extended neutral atmospheres. J. Geophys. Res. 100, 26387–26395 (1995)

    Article  ADS  Google Scholar 

  35. Hornung, K. & Kissel, J. On shock wave impact ionization of dust particles. Astron. Astrophys. 291, 324–336 (1994)

    CAS  ADS  Google Scholar 

  36. Hornung, K., Malama, Y. & Kestenboim, K. Impact vaporization and ionization of cosmic dust particles. Astrophys. Space Sci. 274, 355–363 (2000)

    CAS  Article  ADS  MATH  Google Scholar 

  37. Postberg, F. et al. Composition of Jovian dust stream particles. Icarus 183, 122–134 (2006)

    CAS  Article  ADS  Google Scholar 

  38. Stephan, T. TOF-SIMS in cosmochemistry. Planet. Space Sci. 49, 859–906 (2001)

    CAS  Article  ADS  Google Scholar 

  39. Fiege, K. et al. Compositional analysis of interstellar dust as seen by the Cassini Cosmic Dust Analyser. In 76th Annual Meteoritical Society Meeting, (2013)

  40. Hsu, H.-W. et al. Probing IMF using nanodust measurements from inside Saturn’s magnetosphere. Geophys. Res. Lett. 40, 2902–2906 (2013)

    Article  ADS  Google Scholar 

  41. Shibuya, T. et al. Reactions between basalt and CO2-rich seawater at 250 and 350°C, 500 bars: implications for the CO2 sequestration into the modern oceanic crust and composition of hydrothermal vent fluid in the CO2-rich early ocean. Chem. Geol. 359, 1–9 (2013)

    CAS  Article  ADS  Google Scholar 

  42. Seyfried, W. E., Jr, Foustoukos, D. I. & Fu, Q. Redox evolution and mass transfer during serpentinization: an experimental and theoretical study at 200°C, 500 bar with implications for ultramafic-hosted hydrothermal systems at mid-ocean ridges. Geochim. Cosmochim. Acta 71, 3872–3886 (2007)

    CAS  Article  ADS  Google Scholar 

  43. McCollom, T. M. & Seewald, J. S. Experimental constraints on the hydrothermal reactivity of organic acids and acid anions: I. Formic acid and formate. Geochim. Cosmochim. Acta 67, 3625–3644 (2003)

    CAS  Article  ADS  Google Scholar 

  44. Vance, S. et al. Hydrothermal systems in small ocean planets. Astrobiology 7, 987–1005 (2007)

    CAS  Article  ADS  PubMed  Google Scholar 

  45. Nakamura, T. et al. Chondrulelike objects in short-period comet 81P/Wild 2. Science 321, 1664–1667 (2008)

    CAS  Article  ADS  PubMed  Google Scholar 

  46. Brearley, A. J. in Meteorites and the Early Solar System II (eds Lauretta, D. S. & McSween, H. Y. ) 587–624 (Univ. Arizona Press, 2006)

    Google Scholar 

  47. Ozima, M. Growth of orthoenstatite crystals by the flux method. J. Jpn Assoc. Mineral. Petrol. Econ. Geol. 3 (suppl), 97–103 (1982); in Japanese with English abstract

    Google Scholar 

  48. Tachibana, S., Tsuchiyama, A. & Nagahara, H. Experimental study of incongruent evaporation kinetics of enstatite in vacuum and in hydrogen gas. Geochim. Cosmochim. Acta 66, 713–728 (2002)

    CAS  Article  ADS  Google Scholar 

  49. Johnson, J. W., Oelkers, E. H. & Helgeson, H. C. SUPCRT92: a software package for calculating the standard molal thermodynamic properties of minerals, gases, aqueous species, and reactions from 1 to 5000 bar and 0 to 1000°C. Comput. Geosci. 18, 899–947 (1992)

    Article  ADS  Google Scholar 

  50. Icenhower, J. P. & Dove, P. M. The dissolution kinetics of amorphous silica into sodium chloride solution: effects of temperature and ionic strength. Geochim. Cosmochim. Acta 64, 4193–4203 (2000)

    CAS  Article  ADS  Google Scholar 

  51. Martens, H. R. et al. Observations of molecular oxygen ions in Saturn’s magnetosphere. Geophys. Res. Lett. 35, L20103 (2008)

    Article  ADS  CAS  Google Scholar 

  52. Christon, S. P. et al. Saturn suprathermal O2+ and mass-28+ molecular ions: long-term seasonal and solar variation. J. Geophys. Res. 118, 3446–3463 (2013)

    CAS  Article  Google Scholar 

  53. Kempf, S. et al. The electrostatic potential of E ring particles. Planet. Space Sci. 54, 999–1006 (2006)

    Article  ADS  Google Scholar 

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We acknowledge support from the CDA team, the Cassini project, and NASA. This research was partly supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan, by the Japan Society for the Promotion of Science, and by the Astrobiology Program of the National Institutes of Natural Sciences, Japan. This work was partly supported by the DLR grant 50 OH1103. We thank J. Schmidt, M. Y. Zolotov and D. J. Tobler for discussions, and E. S. Guralnick, J. K. Hillier, A. Rasca and T. Munsat for advice on writing this Letter. Y.S. thanks A. Okubo for her technical help in taking FE-SEM images.

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Authors and Affiliations



H.-W.H., F.P. and Y.S. outlined the study and wrote the Letter. H.-W.H. performed the CDA dynamic analyses with assistance from A.J., M.H. and S.K.; F.P. and S.K. performed the CDA composition analyses; S.K., G.M.-K. and R.S. performed the CDA measurements and initial data processing; F.P. and N.A. performed the CDA mass spectra data acquisition and data reduction; Y.S. performed the experiments and calculations simulating Enceladus’ ocean conditions; T.S. designed the hydrothermal experiments and the analysis system; S.T. synthesized starting minerals for the experiments; K.S., Y.M. and T.K. contributed to performing fluid and solid analyses in the experiments; and S.-i.S. estimated the lifetime of silica nanoparticles in Enceladus’ ocean. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Hsiang-Wen Hsu.

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Extended data figures and tables

Extended Data Figure 1 Maps of grain density, sputtering erosion rate, and stream particle production rate in the E-ring region.

a, The total E-ring ice grain surface area map in the ρz frame, where ρ and z are distance to Saturn’s rotation axis and to the ring plane, respectively. Note that each bin integrates azimuthally over the entire torus, meaning that the outer bins contain a much larger volume than do the inner ones. b, Plasma sputtering erosion rate of E-ring ice grains in torus segments. The total sputtering rate is 8.6 × 1024 H2O molecules per second, lower but still comparable to the 4.5 × 1025 H2O molecules per second derived in ref. 32. c, Normalized nanoparticle production rate in particles per second. RS, Saturn radius.

Extended Data Figure 2 Ejection probability of 5-nm particles from the E ring.

a, For silica nanoparticles, the ejection probability is mostly close to unity (except within 4.5RS). The higher local plasma density there leads to negative dust potential and thus reduces the ejection probability7. The typical timescale for silica nanoparticles to acquire sufficient kinetic energy to escape is of the order of a day7. b, Water ice nanoparticles have lower secondary emission and are charged less positively and thus are less likely to be ejected. This ‘forbidden region’ (the black region) extends further outward to 5.5 RS, consistent with the CDA measurements53.

Extended Data Figure 3 Stream particle emission patterns.

a, Ejection region (ER) profiles, derived from the nanodust and solar wind measurements (blue)7 and the ejection model (red), both peak at 7–9RS. The uncertainty of both profiles stems from the adopted co-rotation fraction of Saturn’s magnetosphere (80–100%), which determines the electromagnetic acceleration amplitude. The location of the outer rim of Saturn’s A ring and the orbits of icy satellites are marked by grey dashed lines. b, Latitudinal-dependent ejection pattern. Scatter and binned stream particle rates (normalized to 25RS distance) are shown in blue squares and crosses, respectively. The vertical length of the crosses represents the standard deviation of the stream particle rate in the corresponding bin. Our model (red) reproduces the measured trend. c, d, Modelled patterns assuming direct ejection from Enceladus. While the ER profile is similar, these particles are only ejected along the ring plane.

Extended Data Figure 4 Energy dispersive spectrum of clustered silica nanoparticles formed from the fluid sample.

See Methods for details.

Extended Data Table 1 Stream particle flux measurements

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Hsu, HW., Postberg, F., Sekine, Y. et al. Ongoing hydrothermal activities within Enceladus. Nature 519, 207–210 (2015).

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