Europlanet Science Congress 2020
Virtual meeting
21 September – 9 October 2020
Europlanet Science Congress 2020
Virtual meeting
21 September – 9 October 2020
EPSC Abstracts
Vol.14, EPSC2020-640, 2020
https://doi.org/10.5194/epsc2020-640
Europlanet Science Congress 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Influence of a thermal boundary layer on the thermal evolution of Uranus and Neptune

Ludwig Scheibe1, Nadine Nettelmann2, and Ronald Redmer1
Ludwig Scheibe et al.
  • 1Universität Rostock, Institut für Physik, Rostock, Germany
  • 2Deutsches Zentrum für Luft und Raumfahrt, Institut für Planetenforschung, Berlin, Germany

It has been a long-standing challenge to reconcile the perceived similarities of Uranus and Neptune with their highly different intrinsic heat fluxes. Previous evolution calculations using the conventional assumption of an adiabatic interior yield too high present-day luminosities or - equivalently - too long cooling times for Uranus  (e.g. [1,2]). For Neptune, however, we found that similar assumptions yield too short cooling times [3].
One proposed mechanism for reproducing the observed brightness is a conducting interface between the hydrogen- and helium-rich outer part and the ice-rich inner part that would inhibit efficient energy transport across it [4]. In this work, we use our recently developed tool for modelling giant planets based on the Henyey-method for stellar 
evolutions [5] to investigate such a conducting interface in the planet's interior, examining the influence of parameters such as assumed layer thickness and thermal conductivity on the cooling behaviour. 
We find that even a thin conductive interface of a few kilometers has significant influence on the planetary cooling. Initially, the presence of such a boundary layer speeds up cooling, while after about 0.1-0.5 Gyr the cooling is slowed down drastically compared to the adiabatic case, similar to what was found for Saturn previously [6]. Our preferred solutions for Uranus suggest equilibrium evolution with the solar incident flux, while for Neptune, we find that plateaus in Teff(t) near its observed value require fine-tuned combinations of layer thickness and thermal conducitivity. 

[1] Fortney, Ikoma, Nettelmann, Guillot, and Marley (2011). ApJ 729, 32
[2] Nettelmann, Helled, Fortney, and Redmer (2013). Planet. Space Sci. 77, 143
[3] Scheibe, Nettelmann, Redmer (2019). A&A 632, A70
[4] Nettelmann, Wang, Fortney, Hamel, Yellamilli, Bethkenhagen, and Redmer (2016). Icarus 275, 107
[5] Henyey, Forbes, and Gould (1964). ApJ 139, 306
[6] Leconte and Chabrier (2013): Nat Geosci. 6, 023007

How to cite: Scheibe, L., Nettelmann, N., and Redmer, R.: Influence of a thermal boundary layer on the thermal evolution of Uranus and Neptune, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-640, https://doi.org/10.5194/epsc2020-640, 2020