Presentation #206.04 in the session The Mist: Outgassing on Enceladus.
The habitability of Enceladus relies on an energy source that supports life. Parkinson et al. (2008) suggested that the redox chemical energy could be the result of the two-way mass exchange between the surface and the ocean. Like Kite and Rubin (2016), we present a model that incorporates displacements of the liquid-vapor interface and thus the mass flux at the surface. This model also helps to explain the secondary peak of plume brightness at mean anomaly (MA) 30-50 degrees, besides the primary peak at mean anomaly (MA) 180 degrees (Hedman et al. 2013, Nimmo et al. 2014, Helfenstein and Porco 2015, Ingersoll et al. 2020).
We modeled the rising and falling of the liquid-vapor interface due to the diurnal expansion and contraction of the walls, which sheds light to the variability of the plumes. We also modeled the water vapor dynamics with a similar method as Nakajima and Ingersoll (2016). In our model, the energy budgets are considered: we have found that the heat storage in the crack walls is able to produce a secondary peak by absorbing heat when the wall is submerged and evaporating when the wall is exposed.
Important parameters in our model are the width, the max-min width ratio, and the thickness of the ice crust. We explored various sets of parameter selections. Depending on parameter choices, we have found that there are two possible mechanisms that creates the observed secondary peak.
Kite and Rubin, 2016. Sustained eruptions on Enceladus explained by turbulent dissipation in tiger stripes. PNAS 113(15) 3972-3975.
Hedman et al., 2013. An observed correlation between plume activity and tidal stresses on Enceladus. Nature 500, 182-184.
Nimmo et al., 2014. Tidally modulated eruptions on Enceladus: Cassini ISS observations and models. The Astronomical Journal, 148 46.
Helfenstein and Porco, 2015. Enceladus’ geysers: relation to geological features. The Astronomical Journal, 150 96.
Ingersoll et al., 2020. Time variability of the Enceladus plumes: Orbital periods, decadal periods, and aperiodic change. Icarus 344, 113345.
Nakajima and Ingersoll, 2016. Controlled boiling on Enceladus. 1. Model of the vapor-driven jets. Icarus 272, 309-318.