Hydro cyclone flow as a physical process of ejection of material in the plumes of Enceladus and influence in the atmosphere.

Abstract

<p>On Enceladus, the first sign of water vapor plumes was detected by the UVIS instrument of Cassini during a stellar occultation in July 2005. The dynamics of these water plumes, probably related to the ocean activity, are an important subject of study in order to understand the exchange of material from this ocean into the atmosphere. There are different theories that might explain the physical processes that allow for the expulsion of material from the subsurface. The formation of these jets could be produced by the sublimation of ice (temperatures below 273 K) rising beneath the hydrostatic pressure along the ice layer or can come from underground boiling liquid that erupts through vents. Other hypothesis assumes that there are regions where the pressure can drop below the saturation vapor pressure of the liquid, allowing for it to boil, so it can produce a pocket of gas in equilibrium with ice grains and liquid water. Another possibility is that the thermal activity in the seafloor of Enceladus creates hot water outflows that locally affect the ice shell and the thinner icy crust in the polar region due to tidal stress. This work presents another possible model for the formation of these vapor plumes. The hydro cyclonic flow could be also a mechanism that produces a constant ejection of these jets and contributes to atmospheric processes. Here we describe a simulation of the dynamic of the energy budget into the atmosphere. Enceladus is tidally locked with Saturn, making the moon spinning around the planet always showing the same face, generating in this way a difference in temperatures between the internal side and the external one. This contrast of temperatures might produce a movement of violent flows of jets on the equator similar to the storms observed on Jupiter. If the tidal axis is not aligned with the major axis, the tidal forces exert a net momentum on the moon, forcing a realignment of the orbit. The result of these processes is a hydro cyclonic flux in the shape of a tornado that eventually generates, due to pressure differences, a straight upwards constant flow that separates the fine particles rising towards the surface from the heavy ones sinking towards the ocean. This hydro cyclonic type of flow might explain the constant jets from the tiger stripes on Enceladus that could decrease when the energy flux received from the sun drops due to the distance between Saturn and the Sun, and the atmospheric and physical conditions are stable.</p>