82-10 Dione Tectonics: A Temporal Framework for Understanding Interior Evolution

Session:

Presenting Author:

Fiona Nichols-Fleming

Authors:

Nichols-Fleming, Fiona¹, Martin, Emily S.², Hammond, Noah P.³, Patthoff, Alex⁴, Watters, Thomas R.⁵

(1) Smithsonian Institution, National Air and Space Museum, Washington, DC, USA, (2) National Air and Space Museum, Washington, DC, USA, (3) Providence College, Providence, RI, USA, (4) Planetary Science Institute, La Habra Heights, CA, USA, (5) Smithsonian Inst, Ctr Earth & Plan Studies/NASM, MRC-315, Washington, DC, USA,

Abstract:

The surface of Dione, the fourth largest moon of Saturn [1], shows abundant evidence of tectonic resurfacing, both contractional and extensional [e.g., 2–4]. However, direct evidence of ongoing geologic activity has so far escaped detection [e.g., 5,6]. The measured gravity field of Dione is based on only four flybys of the Cassini spacecraft, but suggests a high degree of differentiation and is consistent with a subsurface ocean beneath a ~100 km thick water ice crust [7,8]. Thus, Dione provides a complimentary endmember to Enceladus to study the evolution of habitable environments and subsurface oceans, in particular.

 

Here, we use global patterns in tectonics and analysis of the morphology of individual tectonic features to produce observational constraints on the interior structure and thermal state of Dione. Additionally, there appear to be at least two eras of tectonism on Dione: the more recent formation of the Wispy Terrains on the trailing hemisphere and the leading hemisphere, dominated by more ancient tectonic features, including ridges [9]. This allows us to construct a temporal framework within which we can understand how Dione’s interior and thermal budget have changed through time.

 

We find that the orientations of observed ancient tectonics are most consistent with despinning and non-synchronous rotation (NSR) stress fields and orientations of recent tectonics are most consistent with NSR and diurnal tidal stress fields. Additionally, from graben widths within the Wispy Terrain we infer an elastic thickness of ~5-6 km at the time of their formation and therefore surface heat fluxes of ~20-35 mW/m²  ≲1 Ga. These independent results are both consistent with the presence of a long-lived subsurface ocean on Dione.

 

References: [1] Thomas, P. C. (2010) Icarus, 208, 395–401. [2]     Kirchoff, M. R. and Schenk, P. (2015) Icarus, 256, 78–89. [3] Collins, G. C. et al. Planetary Tectonics, Cambridge University Press (2009). [4] Collins, G. C. (2010) AGU 2010, P24A-08. [5] Buratti, B. J. et al. (2011) Icarus, 214, 534–540. [6] Buratti, B. J. et al. (2018) GRL, 45, 5860–5866. [7] Zannoni, M. et al. (2020) Icarus, 345, 113713. [8] Beuthe, M. et al. (2016) GRL, 43, 10,088-10,096. [9] Martin, E. S. et al. (2024) AGU 2024, P31A-09

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10142

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