Another talk by Alex Patthoff examined the relative age dating of Enceladus’ surface to work out the timescales for intense geologic activity inferred from the presence of fractures and grooves. The team suggested that the cause of the extensions that formed these features was the freezing of the entire subsurface liquid ocean, and that the time between periods of geologic activity could be as long as 2 billion years. This echoes the talk by James Roberts, in which he argues that Enceladus’ ocean “wants to freeze,” and can do so in a timespan as short as short as 16 million years if certain assumptions about the heat flux are made. This is consistent with the observations that indicate Enceladus’ ice shell is not in thermal equilibrium at all, which opens up entirely new questions on why that is.

Cryovolcanism is important to study because the material ejected out from the plumes comes directly from within the planet and contains clues for what may lie beneath the icy exterior. But the ice shell itself holds mysteries too. Chaos is a feature unique to Europa, but the mechanics behind its formation are still unknown. All models agree it has something to do with melting, shifting, and refreezing at least the top layer of the ice shell, but how deep does that melting go? The models must also explain why chaos only occurs on Europa, as far as we have seen in space missions to date.