New Insights Into Temperature-dependent Ice Properties And Their Effect On Ice shell Convection For Icy Ocean Worlds

Ice shell stability with temperature-dependent thermal conductivity (Π = 0): (a) Regime diagram with the stability boundary in RaΘ-space. Parameter ranges relevant to Enceladus, Europa and Titan are indicated. The red circle gives the parameter combination (Ra = 6.5 · 106 , θ = 0.33/Ts = 90 K) for temperature fields and streamlines shown in panels (b-e) with four different k(T) relations: (b) constant: k = k(Tb) = 2.26 W m−1 K−1 , (c) Hobbs (1974), (d) this work, (e) Rabin (2000).

Ice shell dynamics are an important control on the habitability of icy ocean worlds. Here we present a systematic study evaluating the effect of temperature-dependent material properties on these dynamics.

We review the published thermal conductivity data for ice, which demonstrates that the most commonly used conductivity model in planetary science represents a lower bound. We propose a new model for thermal conductivity that spans the temperature range relevant to the ice shells of ocean worlds. This increases the thermal conductivity at low temperatures near the surface by about a fifth. We show that such an increase in thermal conductivity near the cold surface can stabilizes the ice shell of Europa. Furthermore, we show that including temperature dependent specific heat capacity decreases the energy stored in the conductive lid which reduces the response timescale of the ice shell to thermal perturbations by approximately a third. This may help to explain surface features such as chaotic terrains that require large additions of energy to the near-surface ice.

Evan Carnahan, Natalie S. Wolfenbarger, Jacob S. Jordan, Marc A. Hesse

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2011.12502 [astro-ph.EP] (or arXiv:2011.12502v1 [astro-ph.EP] for this version)
Submission history
From: Evan Carnahan [view email]
[v1] Wed, 25 Nov 2020 03:47:17 UTC (6,194 KB)

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