Evidence of non-uniform crust of Ceres from Dawn’s high-resolution gravity data
R. S. Park, A. S. Konopliv, A. I. Ermakov, J. C. Castillo-Rogez, R. R. Fu, K. H. G. Hughson, T. H. Prettyman, C. A. Raymond, J. E. C. Scully, H. G. Sizemore, M. M. Sori, A. T. Vaughan, G. Mitri, B. E. Schmidt & C. T. Russell
Nature Astronomy, Volume 4, pages 748–755 (2020)
“The gravity and shape data acquired by the Dawn spacecraft during its primary mission revealed that Ceres is partially differentiated with an interior structure consistent with a volatile-rich crust, a mantle of hydrated rock and isostatically compensated topography. Detailed analyses showed that the mechanically strong crust overlays a weak, fluid-bearing upper mantle. Previous studies, however, assumed that Ceres’s crust is a uniform layer. Here, we report findings from the new high-resolution gravity data from Dawn’s second extended mission (XM2), which reveal a complex crustal structure of Ceres. In the low-altitude regions probed by the Dawn spacecraft during the XM2 phase, we observe that gravity–topography admittance progressively shifts to a lower density solution at higher degrees, implying a radial density gradient across Ceres’s crust that is consistent with decreasing porosity with depth and/or increasing content of dense phases, such as rock and salts. That gradient brings a critical new constraint on the crustal freezing history, suggesting that the salts and silicates concentrated in the liquid phase while the crust was growing. Localized spectral analysis of the new data also shows evidence for a lower crustal density in the north polar region than in the south or near the equator, supporting impact-driven porosity variations for the observed latitudinal density differences. On the local scale, the new data show evidence for density or rheological variations within the crust, in association with lobate landslides and ejecta deposits that were inferred to be ice-rich as well as an extensional fault system8. These inferences provide geophysical context for geological features on the surface and help us advance our understanding of the evolution of an ice-rich but heat-starved body, whose evolution was in part shaped by impacts.”
