Article | Published:

Evolution of Saturn’s mid-sized moons

Nature Astronomy (2019) | Download Citation


The orbits of Saturn’s inner mid-sized moons (Mimas, Enceladus, Tethys, Dione and Rhea) have been notably difficult to reconcile with their geology. Here we present numerical simulations coupling thermal, geophysical and simplified orbital evolution for 4.5 billion years that reproduce the observed characteristics of their orbits and interiors, provided that the outer four moons are old. Tidal dissipation within Saturn expands the moons’ orbits over time. Dissipation within the moons decreases their eccentricities, which are episodically increased by moon−moon interactions, causing past or present oceans to exist in the interiors of Enceladus, Dione and Tethys. In contrast, Mimas’s proximity to Saturn’s rings generates interactions that cause such rapid orbital expansion that Mimas must have formed only 0.1−1 billion years ago if it postdates the rings. The resulting lack of radionuclides keeps it geologically inactive. These simulations explain the Mimas−Enceladus dichotomy, reconcile the moons’ orbital properties and geological diversity, and self-consistently produce a recent ocean on Enceladus.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Data availability

All data generated or analysed during this study are included in this published article and Supplementary Information. The code used to generate those data is freely available at

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


  1. 1.

    Kirchoff et al. in Enceladus and the Icy Moons of Saturn 267–284 (Univ. of Arizona Press, 2018).

  2. 2.

    Lainey et al. New constraints on Saturn’s interior from Cassini astrometric data. Icarus 281, 286–296 (2017).

  3. 3.

    Ćuk, M., Dones, L. & Nesvorný, D. Dynamical evidence for a late formation of Saturn’s moons. Astrophys. J. 820, 97 (2016).

  4. 4.

    Asphaug, E. & Reufer, A. Late origin of the Saturn system. Icarus 223, 544–565 (2013).

  5. 5.

    Canup, R. M. Origin of Saturn’s rings and inner moons by mass removal from a lost Titan-sized satellite. Nature 468, 943–946 (2010).

  6. 6.

    Movshovitz, N., Nimmo, F., Korycansky, D. G., Asphaug, E. & Owen, J. M. Disruption and reaccretion of midsized moons during an outer solar system late heavy bombardment. Geophys. Res. Lett. 42, 256–263 (2015).

  7. 7.

    Charnoz, S. et al. Accretion of Saturn’s mid-sized moons during the viscous spreading of young massive rings: solving the paradox of silicate-poor rings versus silicate-rich moons. Icarus 216, 535–550 (2011).

  8. 8.

    Beuthe, M., Rivoldini, A. & Trinh, A. Enceladus’s and Dione’s floating ice shells supported by minimum stress isostasy. Geophys. Res. Lett. 43, 10088–10096 (2016).

  9. 9.

    Čadek, O. et al. Enceladus’s internal ocean and ice shell constrained from Cassini gravity, shape, and libration data. Geophys. Res. Lett. 43, 5653–5660 (2016).

  10. 10.

    McKinnon, W. B. Effect of Enceladus’s rapid synchronous spin on interpretation of Cassini gravity. Geophys. Res. Lett. 42, 2137–2143 (2015).

  11. 11.

    Tajeddine, R. et al. Constraints on Mimas’ interior from Cassini ISS libration measurements. Science 346, 322–324 (2014).

  12. 12.

    Tortora, P. et al. Rhea gravity field and interior modeling from Cassini data analysis. Icarus 264, 264–273 (2016).

  13. 13.

    Thomas, P. C. et al. Enceladus’s measured physical libration requires a global subsurface ocean. Icarus 264, 37–47 (2016).

  14. 14.

    Hsu, H.-W. et al. Ongoing hydrothermal activities within Enceladus. Nature 519, 207–210 (2015).

  15. 15.

    Waite, J. H. et al. Cassini finds molecular hydrogen in the Enceladus plume: evidence for hydrothermal processes. Science 356, 155–159 (2017).

  16. 16.

    Porco, C. C. et al. Cassini observes the active south pole of Enceladus. Science 311, 1393–1401 (2006).

  17. 17.

    Bland, M. T., McKinnon, W. B. & Schenk, P. M. Constraining the heat flux between Enceladus’ tiger stripes: numerical modeling of funiscular plains formation. Icarus 260, 232–245 (2015).

  18. 18.

    Howett, C. J. A., Spencer, J. R., Pearl, J. & Segura, M. High heat flow from Enceladus' south polar region measured using 10–600 cm−1 CASSINI/CIRS data. J. Geophys. Res. Planet. 116, E03003 (2011).

  19. 19.

    Spencer, J. R. et al. Enceladus heat flow from high spatial resolution thermal emission observations. Eur. Planet. Sci. Congr. Abstr. 8, 840–841 (2013).

  20. 20.

    Neveu, M. & Rhoden, A. R. The origin and evolution of a differentiated Mimas. Icarus 296, 183–196 (2017).

  21. 21.

    Rhoden, A. R., Henning, W., Hurford, T. A., Patthoff, D. A. & Tajeddine, R. The implications of tides on the Mimas ocean hypothesis. J. Geophys. Res. Planet. 122, 400–410 (2017).

  22. 22.

    Czechowski, L. & Witek, P. Comparison of early evolutions of Mimas and Enceladus. Acta Geophys. 63, 900–921 (2015).

  23. 23.

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

  24. 24.

    Schubert, G., Anderson, J. D., Travis, B. J. & Palguta, J. Enceladus: present internal structure and differentiation by early and long-term radiogenic heating. Icarus 188, 345–355 (2007).

  25. 25.

    Shoji, D., Hussmann, H., Sohl, F. & Kurita, K. Non-steady state tidal heating of Enceladus. Icarus 235, 75–85 (2014).

  26. 26.

    Travis, B. J. & Schubert, G. Keeping Enceladus warm. Icarus 250, 32–42 (2015).

  27. 27.

    Zhang, K. & Nimmo, F. Late-stage impacts and the orbital and thermal evolution of Tethys. Icarus 218, 348–355 (2012).

  28. 28.

    Meyer, J. & Wisdom, J. Tidal evolution of Mimas, Enceladus, and Dione. Icarus 193, 213–223 (2008).

  29. 29.

    Zhang, Z. et al. Cassini microwave observations provide clues to the origin of Saturn’s C ring. Icarus 281, 297–321 (2017).

  30. 30.

    Zhang, Z. et al. VLA multi-wavelength microwave observations of Saturn’s C and B rings. Icarus 317, 518–548 (2019).

  31. 31.

    Charnoz, S., Morbidelli, A., Dones, L. & Salmon, J. Did Saturn’s rings form during the late heavy bombardment? Icarus 199, 413–428 (2009).

  32. 32.

    Hyodo, R., Charnoz, S., Ohtsuki, K. & Genda, H. Ring formation around giant planets by tidal disruption of a single passing large Kuiper belt object. Icarus 282, 195–213 (2017).

  33. 33.

    Dubinski, J. A recent origin for Saturn’s rings from the collisional disruption of an icy moon. Icarus 321, 291–306 (2019).

  34. 34.

    Fuller, J., Luan, J. & Quataert, E. Resonance locking as the source of rapid tidal migration in the Jupiter and Saturn moon systems. Mon. Not. R. Astron. Soc. 458, 3867–3879 (2016).

  35. 35.

    Robbins, S. et al. Estimating the masses of Saturn’s A and B rings from high-optical depth n-body simulations and stellar occultations. Icarus 206, 431–445 (2010).

  36. 36.

    Grossmann, L. Saturn’s rings are surprisingly young and may be from shredded moons. Sci. News 193, 7 (2018).

  37. 37.

    Choblet, G. et al. Powering prolonged hydrothermal activity inside Enceladus. Nat. Astron. 1, 841–847 (2017).

  38. 38.

    Roberts, J. H. The fluffy core of Enceladus. Icarus 258, 54–66 (2015).

  39. 39.

    Tyler, R. Comparative estimates of the heat generated by ocean tides on icy satellites in the outer solar system. Icarus 243, 358–385 (2014).

  40. 40.

    Sekine, Y. et al. High-temperature water-rock interactions and hydrothermal environments in the chondrite-like core of Enceladus. Nat. Commun. 6, 8604 (2015).

  41. 41.

    Meyer, J. & Wisdom, J. Tidal heating in Enceladus. Icarus 188, 535–539 (2007).

  42. 42.

    Roberts, J. H. & Nimmo, F. Tidal heating and the long-term stability of a subsurface ocean on Enceladus. Icarus 194, 675–689 (2008).

  43. 43.

    Dermott, S. F. & Thomas, P. C. The shape and internal structure of Mimas. Icarus 73, 25–65 (1988).

  44. 44.

    Malhotra, R. Orbital resonances and chaos in the Solar System. In Solar System Formation and Evolution Vol. 149 (eds Lazzaro, D., Vieira Martins, R., Ferraz-Mello, S. & Fernandez, J.) 37 (ASP Conference Series, 1998).

  45. 45.

    Desch, S. J., Cook, J. C., Doggett, T. C. & Porter, S. B. Thermal evolution of Kuiper belt objects, with implications for cryovolcanism. Icarus 202, 694–714 (2009).

  46. 46.

    Rubin, M. E., Desch, S. J. & Neveu, M. The effect of Rayleigh–Taylor instabilities on the thickness of undifferentiated crust on Kuiper belt objects. Icarus 236, 122–135 (2014).

  47. 47.

    Neveu, M., Desch, S. J. & Castillo-Rogez, J. C. Core cracking and hydrothermal circulation can profoundly affect Ceres’ geophysical evolution. J. Geophys. Res. Planet. 120, 123–154 (2015).

  48. 48.

    Lodders, K. Solar system abundances and condensation temperatures of the elements. Astrophys. J. 591, 1220 (2003).

  49. 49.

    Tobie, G., Mocquet, A. & Sotin, C. Tidal dissipation within large icy satellites: applications to Europa and Titan. Icarus 177, 534–549 (2005).

  50. 50.

    Sabadini, R. & Vermeersen, B. in Global Dynamics of the Earth 1–44 (Springer, 2004).

  51. 51.

    Meyer-Vernet, N. & Sicardy, B. On the physics of resonant disk-satellite interaction. Icarus 69, 157–175 (1987).

  52. 52.

    Nakajima, A., Ida, S., Kimura, J. & Brasser, R. Orbital evolution of Saturn’s mid-sized moons and the tidal heating of Enceladus. Icarus 317, 570–582 (2019).

  53. 53.

    Henning, W. G. & Hurford, T. Tidal heating in multilayered terrestrial exoplanets. Astrophys. J. 789, 30 (2014).

  54. 54.

    Chambers, J. E. A hybrid symplectic integrator that permits close encounters between massive bodies. Mon. Not. R. Astron. Soc. 304, 793–799 (1999).

  55. 55.

    Greenberg, R., Wacker, J. F., Hartmann, W. K. & Chapman, C. R. Planetesimals to planets: numerical simulation of collisional evolution. Icarus 35, 1–26 (1978).

  56. 56.

    Zhang, K. & Nimmo, F. Recent orbital evolution and the internal structures of Enceladus and Dione. Icarus 204, 597–609 (2009).

  57. 57.

    Noyelles, B., Baillie, K., Lainey, V. & Charnoz, S. How Mimas cleared the Cassini division. AAS/DPS Meet. Abstr. 48, 121.07 (2016).

  58. 58.

    Dermott, S. F., Malhotra, R. & Murray, C. D. Dynamics of the Uranian and Saturnian satellite systems: a chaotic route to melting Miranda? Icarus 76, 295–334 (1988).

  59. 59.

    Tsiganis, K., Gomes, R., Morbidelli, A. & Levison, H. F. Origin of the orbital architecture of the giant planets of the Solar System. Nature 435, 459–461 (2005).

  60. 60.

    Barnes, R., Deitrick, R., Greenberg, R., Quinn, T. R. & Raymond, S. N. Long-lived chaotic orbital evolution of exoplanets in mean motion resonances with mutual inclinations. Astrophys. J. 801, 101 (2015).

  61. 61.

    Borderies, N. & Goldreich, P. A simple derivation of capture probabilities for the j+1:j and j + 2:j orbit-orbit resonance problems. Celestial Mech. 32, 127–136 (1984).

  62. 62.

    Wisdom, J. Tidal dissipation at arbitrary eccentricity and obliquity. Icarus 193, 637–640 (2008).

  63. 63.

    Greenberg, R. Orbit-orbit resonances in the solar system: varieties and similarities. Vistas Astron. 21, 209–239 (1977).

  64. 64.

    Sekine, Y. & Genda, H. Giant impacts in the Saturnian system: a possible origin of diversity in the inner mid-sized satellites. Planet. Space Sci. 63, 133–138 (2012).

  65. 65.

    Salmon, J. & Canup, R. M. Accretion of Saturn’s inner mid-sized moons from a massive primordial ice ring. Astrophys. J. 836, 109 (2017).

  66. 66.

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

  67. 67.

    Shoji, D. & Hussmann, H. Frequency-dependent tidal dissipation in a viscoelastic Saturnian core and expansion of Mimas’ semi-major axis. Astron. Astrophys. 599, L10 (2017).

  68. 68.

    Charnoz, S., Salmon, J. & Crida, A. The recent formation of Saturn’s moonlets from viscous spreading of the main rings. Nature 465, 752–754 (2010).

  69. 69.

    Salmon, J., Charnoz, S., Crida, A. & Brahic, A. Long-term and large-scale viscous evolution of dense planetary rings. Icarus 209, 771–785 (2010).

  70. 70.

    Howett, C. J. A., Spencer, J. R., Pearl, J. & Segura, M. Thermal inertia and bolometric bond albedo values for Mimas, Enceladus, Tethys, Dione, Rhea and Iapetus as derived from Cassini/CIRS measurements. Icarus 206, 573–593 (2010).

  71. 71.

    Thomas, P. C. Sizes, shapes, and derived properties of the Saturnian satellites after the Cassini nominal mission. Icarus 208, 395–401 (2010).

  72. 72.

    Jacobson, R. A. et al. The gravity field of the Saturnian system from satellite observations and spacecraft tracking data. Astron. J. 132, 2520 (2006).

  73. 73.

    Bland, M. T., Singer, K. N., McKinnon, W. B. & Schenk, P. M. Enceladus’ extreme heat flux as revealed by its relaxed craters. Geophys. Res. Lett. 39, L17204 (2012).

  74. 74.

    Bland, M. T., Beyer, R. A. & Showman, A. P. Unstable extension of Enceladus’ lithosphere. Icarus 192, 92–105 (2007).

  75. 75.

    Giese, B. et al. Enceladus: an estimate of heat flux and lithospheric thickness from flexurally supported topography. Geophys. Res. Lett. 35, L24204 (2008).

  76. 76.

    White, O. L. et al. Impact crater relaxation on Dione and Tethys and relation to past heat flow. Icarus 288, 37–52 (2017).

  77. 77.

    Hammond, N. P., Phillips, C. B., Nimmo, F. & Kattenhorn, S. A. Flexure on Dione: investigating subsurface structure and thermal history. Icarus 223, 418–422 (2013).

  78. 78.

    Nimmo, F., Bills, B. G., Thomas, P. C. & Asmar, S. W. Geophysical implications of the long-wavelength topography of Rhea. J. Geophys. Res. Planet. 115, E10008 (2010).

Download references


This research was funded by A.R.R.’s startup funds at Arizona State University and NASA’s Cassini Data Analysis Program award NNX16AI42G. We thank S. Desch for providing access to the computers on which the model was developed and simulations were run.

Author information


  1. Department of Astronomy, University of Maryland, College Park, MD, USA

    • Marc Neveu
  2. CRESST II and Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA

    • Marc Neveu
  3. Southwest Research Institute, Boulder, CO, USA

    • Alyssa R. Rhoden


  1. Search for Marc Neveu in:

  2. Search for Alyssa R. Rhoden in:


M.N. developed the models and ran the simulations. M.N. and A.R.R. designed the research and interpreted the results.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Marc Neveu.

Supplementary information

  1. Supplementary Information

    Supplementary Text, Supplementary Figures 1–12, Supplementary Table 1, description of Supplementary Data 1–12, Supplementary References.

  2. Supplementary Data 1

    Contains the data necessary to reproduce Figure 2.

  3. Supplementary Data 2

    Contains the data necessary to reproduce Figure 3.

  4. Supplementary Data 3

    Contains the data necessary to reproduce Supplementary Figure 1.

  5. Supplementary Data 4

    Contains the data necessary to reproduce Supplementary Figure 2.

  6. Supplementary Data 5

    Contains the data necessary to reproduce Supplementary Figure 3.

  7. Supplementary Data 6

    Contains the data necessary to reproduce Supplementary Figure 4.

  8. Supplementary Data 7

    Contains the data necessary to reproduce Supplementary Figure 5.

  9. Supplementary Data 8

    Contains the data necessary to reproduce Supplementary Figure 7.

  10. Supplementary Data 9

    Contains the data necessary to reproduce Supplementary Figure 8.

  11. Supplementary Data 10

    Contains the data necessary to reproduce Supplementary Figure 9.

  12. Supplementary Data 11

    Contains the data necessary to reproduce Supplementary Figure 10.

  13. Supplementary Data 12

    Contains the data necessary to reproduce Supplementary Figure 11.

About this article

Publication history