Modelling the Rock-Water Interactions in the Sub-surface Environment of Enceladus

Hamp, Rachael; Olsson-Francis, Karen; Schwenzer, Susanne; Ramkissoon, Nisha and Pearson, Victoria (2019). Modelling the Rock-Water Interactions in the Sub-surface Environment of Enceladus. In: Goldschmidt Conference 2019, 18-23 Aug 2019, Barcelona.



Understanding the geochemical cycles occuring at the rock-water interface on Enceladus is crucial in establishing the potential habitability of the sub-surface environment. The work to be presented focuses on the early ocean’s interaction with the silicate interior, with future work exploring the modern-day sub-surface environment on Enceladus.

In preliminary studies we have used thermochemical modelling (CHIM-XPT) [1] to determine the chemical composition of the sub-surface ocean. The modelling focuses on the interaction of an ‘initial’ ocean chemistry with a defined silicate interior [2] to generate a modern ocean composition. We have defined the chemistry for the silicate interior based upon the chemical composition of a CI carbonaceous chondrite [3].

In the preliminary modelling we have used two different ‘initial’ compositions for the sub-surface ocean that represent different theories on its origin. The first uses a dilute sodium chloride solution, based upon the assumption that the subsurface ocean originated as almost pure water [4]. The second is based upon the assumption that the water originated from melted cometary ice [5], with a cometary composition based upon data collected from 67P [6]. We have explored the full temperature and pressure ranges anticipated at the rock-water interface. We will present the results from this preliminary
modelling, the output of which will generate a modern-day ocean composition. This will be used in subsequent modelling and simulation experiments.

We then plan to model the modern-day sub-surface environment to understand the full range of chemical cycles occurring at the rock-water interface. We will use the subsurface ocean composition determined by the preliminary modelling and the chemistry for the silicate interior that has already been defined. This work will have a specific focus on carbon cycling occurring within the sub-surface environment, gaining a better understanding about the potential habitability of this environment.

[1] Reed, M. H., Spycher, N. F., Palandri, J., (2010) User guide for
CHIM-XPT, University of Oregon, Oregon
[2] Hamp R. E. et al., (2019), 50th LPSC 2019, Abstract 1091
[3] Zolotov, M., (2007) Geophys Res Let, L23203
[4] Brown R. H. et al, (2006) Science, 311, 1425-1428
[5] Neveu, M., et al., (2017) Geochim et Cosmochim, 212, 324-371 [6] Hertier K. H., et al., (2017) RAS monthly notices, 469

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