On the structure and long-term evolution of ice-rich bodies

Status Report From: e-Print archive
Posted: Friday, January 14, 2022

Stephan Loveless, Dina Prialnik, Morris Podolak

The interest in the structure of ice-rich planetary bodies, in particular the differentiation between ice and rock, has grown due to the discovery of Kuiper belt objects and exoplanets. We thus carry out a parameter study for a range of planetary masses M, yielding radii $50 \aplt R \aplt 3000$~km, and for rock/ice mass ratios between 0.25 and 4, evolving them for 4.5~Gyr in a cold environment, to obtain the present structure. We use a thermal evolution model that allows for liquid and vapor flow in a porous medium, solving mass and energy conservation equations under hydrostatic equilibrium for a spherical body in orbit around a central star. The model includes the effect of pressure on porosity and on the melting temperature, heating by long-lived radioactive isotopes, and temperature-dependent serpentinization and dehydration. We obtain the boundary in parameter space [size, rock-content] between bodies that differentiate, forming a rocky core, and those which remain undifferentiated: small bodies, bodies with a low rock content, and the largest bodies considered, which develop high internal pressures and barely attain the melting temperature. The final differentiated structure comprises a rocky core, an ice-rich mantle, and a thin dense crust below the surface. We obtain and discuss the bulk density-radius relationship. The effect of a very cold environment is investigated and we find that at an ambient temperature of ∼20~K, small bodies preserve the ice in amorphous form to the present.

Comments: 21 pages, 12 figures, accepted for publication in Ap.J

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:2201.02976 [astro-ph.EP] (or arXiv:2201.02976v1 [astro-ph.EP] for this version)

Submission history

From: Morris Podolak 

[v1] Sun, 9 Jan 2022 10:08:37 UTC (2,902 KB)

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