Presentation #114.03 in the session MBAs: Physical Characteristics, Part 1.
Volatile components in small bodies provides important clues on the solar system evolution and are of resource exploration interest. In recent decades, outgassing-like activity has been detected on several asteroids located in the inner solar system, indicating the possible existence of buried ices in these bodies . Prior theoretical studies (e.g., [2, 3]) using spherical shapes predict that bodies with diameters of 10 km or larger in the outer main belt should have retained interior water ice for over 4.5 Gyr. To date, there has been no extension of this analysis to small bodies with complex shapes and realistic orbital properties. Explicit modeling of the interior thermal evolution and gas diffusion is thus necessary to accurately calculate the interior ice evolution for more complicated and realistic small-body models. However, the current numerical studies commonly use the finite difference method, which has limited capability in simulating the global long-duration thermal dynamics of icy small bodies, especially when gas diffusion is involved.
In this study, we developed a novel 3D framework using the mesh-free generalized finite difference method (GFDM)  for modeling long-duration heat conduction and rarefied gas flows in a porous small body. By using a spherical body as an example, we found that the timescale to achieve thermal equilibrium is comparable with theoretical estimate and the surface and interior temperature distributions are in good agreement with theoretical estimates. Our simulation results reveal that ice sublimation mainly occurs near the ice front and ice condensation can occur closely beneath the ice front. The gas density at the surface is highly sensitive to the depth-to-ice. By comparing with the dust levitation gas density threshold, we predict that subsurface ice at a depth ≳1 m could exist for those bodies that do not show cometary activities currently, and this interior ice content can be detectable from the surface gas emission by in-situ investigation.
References:  Jewitt et al., The active asteroids, Asteroid IV (P. Michel et al. ed.), 221-241 (2015).  Schörghofer, ApJ 682, 697-705 (2008).  Schörghofer & Hsieh, JGR: Planets 123, 2322-2335 (2018).  L. Gavete et al., Applied Mathematical Modelling 40, 955-965 (2016).
Acknowledgements: This work was supported by NASA Grant 80NSSC20K1079.