Ceres’ Broad‐Scale Surface Geomorphology Largely Due To Asymmetric Internal Convection

• Published in: AGU advances 2022-06, Vol.3 (3), p.n/a
• Main Authors: King, Scott D., Bland, Michael T., Marchi, Simone, Raymond, Carol A., Russell, Christopher T., Scully, Jennifer E. C., Sizemore, Hanna G.
• Format: Article
• Language: English
• Subjects: Carbonates; Ceres; Convection; Geomorphology; Hanami Planum; Heat conductivity; Hydrates; icy bodies; mantle convection; Potassium; Radioisotopes; Rayleigh number; Rheology; Viscosity
• ISSN: 2576-604X; 2576-604X
• DOI: 10.1029/2021AV000571

While we now know much about the volatile‐rich world of Ceres from the Dawn mission, the deep interior remains something of an enigma, shrouded by a crust composed of water ice, carbonates, phyllosilicates, salts and clathrate hydrates. While smaller than most active moons or planets, Ceres has many features commonly associated with active, icy bodies including: hydrothermal, cryovolcanic, and tectonic features. Yet on active icy moons tidal heating is a significant component of the thermal budget; it is unclear whether radiogenic heating alone would be sufficient to supply the heat necessary for Ceres' interior to undergo solid‐state convection. Here we show that transient asymmetric convection develops as the temperature within the body rises from heat generated by the decay of long‐lived radionuclides (e.g., U, Th, K). The onset of transient asymmetric convection may reconcile a number of puzzling features on Ceres including: the missing large craters, Hanami Planum—the region of thickened crust, the gravity and crustal thickness, and the lithospheric stress state represented by the Samhain Catenae. Hemispheric‐scale instabilities may also be important in the evolution of small bodies with small cores throughout the solar system, including the small icy moons of Saturn and Uranus as well as Kuiper belt objects. Plain Language Summary Ceres is the largest body in the asteroid belt. Because Ceres is small, there was not enough gravitational energy when it formed to heat the interior. We investigate whether heat generated by the decay of radiogenic elements can power the tectonism, ice‐volcanism, and evidence for past hydrothermal activity that have been documented by the Dawn mission. Using computer modeling, we find a planet‐scale asymmetric instability (one hemisphere up, one hemisphere down) forms as a small spherical body heats due to the decay of radiogenic elements within the interior. We show that this planet‐scale instability can explain many puzzling features on Ceres including: the high topographic plateau, fracture zones, and the absence of large craters. We suggest that planet‐scale instabilities may play a role in the dynamics of other small icy bodies in the solar system. Key Points As small bodies warm due to radiogenic heating, they undergo a hemisphere‐scale instability with one hemisphere rising and the other sinking On Ceres, a hemispheric‐scale instability can explain the absence of large craters, large topographic plateaus, and tecton