Ceres

An Ancient And Impure Frozen Ocean On Ceres Implied By Its Ice-rich Crust

By Keith Cowing

Status Report

Nature

September 30, 2024

Filed under Ceres, Craters, Dawn, dwarf planet, geology, ice, icy world, Nature, Ocean world

An Ancient And Impure Frozen Ocean On Ceres Implied By Its Ice-rich Crust — This simulation was run in a uniformly 90% ice crust (Fig. 1a) at the equator and shows total vertical displacement after 1 Gyr of relaxation. The black lines are the initial state of the simulation, and the solid colour shows the final state of the simulation. In this case, the crater has only shallowed by ~70 m from an initial depth of 2,400 m (seen as the solid colour at the centre of the crater slightly offset from the black line), for a relaxation percentage of <4%. -- Nature

Ceres is a key object in understanding the evolution of small bodies and is the only dwarf planet to have been orbited by a spacecraft, NASA’s Dawn mission.

Dawn data paint an inconclusive picture of Ceres’ internal structure, composition and evolutionary pathway: crater morphology and gravity inversions suggest an ice-rich interior, while a lack of extensive crater relaxation argues for low ice content.

Here we resolve this discrepancy by applying an ice rheology that includes effects of impurities on grain boundary sliding to finite element method simulations of Cerean craters.

We show that Ceres can maintain its cratered topography while also having an ice-rich crust. Our simulations show that a crust with ~90% ice near the surface, which gradually decreases to 0% at 117 km depth, simultaneously matches the observed lack of crater relaxation, observed crater morphology and gravity inversions.

This crustal structure results from a frozen ocean that became more impurity rich as it solidified top-down. Therefore, the Dawn data are consistent with an icy Ceres that evolved through freezing of an ancient, impure ocean.

An ancient and impure frozen ocean on Ceres implied by its ice-rich crust, Nature (open access)

Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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