High-resolution data of Ceres’s bright spots (faculae), obtained by Dawn’s second extended mission, suggest the existence of a deep brine-rich reservoir that emerged to the surface through long-lived cryovolcanic activity as a consequence of the impact that created Occator crater.
Dawn XM2 at Occator crater
Close to the end of its mission, the Dawn spacecraft performed high resolution observations of Occator crater at Ceres in order to study its bright points (faculae) at unprecedented detail. These observations establish Ceres as an ocean world.
Spectroscopic data obtained at high spatial resolution from Dawn detected the presence of fresh chloride salts at Cerealia Facula on Ceres. The spatial distribution of the hydration level of these salts suggests that they surfaced a maximum of a few centuries ago and that the upwelling of salty fluids may still be active.
Mounds within Ceres’s Occator crater may have formed by freezing of water-rich impact-induced melt, by a process analogous to that of pingo formation on Earth, according to an analysis of data from NASA’s Dawn mission.
The varied sources of faculae-forming brines in Ceres’ Occator crater emplaced via hydrothermal brine effusion
The second extended phase of the Dawn mission provided high resolution observations of Occator crater of the dwarf planet Ceres. Here, the authors show that the central faculae were sourced in an impact-induced melt chamber, with a contribution from the deep brine reservoir, while the Vinalia Faculae were sourced by the deep brine reservoir alone.
High-spatial-resolution images of the bright points at Occator crater on Ceres, taken during the second extended Dawn mission, allowed reconstruction of the chronology of their formation. The area experienced extensive cryovolcanism less than nine million years ago that lasted several million years, indicating recent geological activity.
High-resolution gravity data from Dawn’s second extended mission could probe the global and local structure of Ceres’s crust. The results show significant spatial and vertical variations of crustal density and porosity, associated with ice features and ice-related processes driven from the interior, and impacts.
Impact heat driven volatile redistribution at Occator crater on Ceres as a comparative planetary process
Dawn mission’s second extended phase provided high resolution observations of Occator crater of the dwarf planet Ceres. Here, the authors show stereo imaging and topographic maps of this crater revealing the influence of crustal composition on impact related melt and hydrothermal processes, and compare features to those on Mars, Earth and the Moon.
Long believed to be a primitive body, Ceres is now an ocean world with deep brines at a regional and potentially global scale. Further studies at Ceres’s conditions and — above all — a follow-up mission are needed to study its evolution and potential habitability.
In its second extended mission at Ceres, the Dawn spacecraft returned a harvest of high-resolution data on the intriguing Occator crater, a landmark for understanding the role of impacts in shaping ice-rich bodies, explain Project Scientist Julie Castillo-Rogez and Chief Engineer Marc Rayman.
NASA's Dawn orbiter probe has revealed localized bright areas on the surface of the dwarf asteroid-belt planet Ceres, most prominently in the Occator crater. These features were tentatively interpreted as containing a large amount of hydrated magnesium sulfates. Now Maria Cristina De Sanctis et al. present high-resolution near-infrared spectra of the Occator bright areas that suggest that the bright material consists mostly of endogenous sodium carbonate, mixed with a dark component and small amounts of phyllosilicates, as well as ammonium carbonate or ammonium chloride. The authors propose that these compounds are residues from the crystallization of brines, following upwelling through nearby fracture systems, together with entrained altered solids that reached the surface from below. Such a model requires a heat source, which may have been transient, triggered by impact heating for instance. Alternatively, internal temperatures may be above the eutectic temperature of subsurface brines, in which case fluids may exist at depth on Ceres today.
Images from NASA's Dawn orbiter spacecraft reveal localized bright areas on the surface of the dwarf planet Ceres, the largest object in the main asteroid belt. These unusual areas are consistent with the presence of hydrated magnesium sulfates mixed with dark background material, although other compositions are possible. Recent reports of water vapour, bound water and OH on Ceres raised the possibility there may be surface water there, and the new images reveal multiple bright spots on the floor of crater Occator that could be from surface ice. The largest of these, corresponding to the crater's central pit, produces haze clouds inside the crater with a diurnal rhythm, a clear indication of possible sublimation of water ice.
The identification and dating of ~30 cryovolcanic domes on Ceres from Dawn data shows that cryovolcanism has been continuous on the dwarf planet at least for the last 2.5 Gyr, but not at rates comparable with standard volcanism on terrestrial planets.
Domes on the dwarf planet Ceres could form by solid-state flow of low-density, ice-rich parts of its crust—a process analogous to salt doming on Earth—according to numerical simulations.
Studying craters on atmosphere-less bodies can unlock information about planetesimal histories. Here, Marchi et al. present results from the NASA Dawn mission to Ceres showing that craters >100–150 km in size are largely absent, and find that Ceres’ internal evolution is responsible for their absence.
The dwarf planet Ceres is thought to have an ice-rich layer in its shallow subsurface. The morphologies of craters, however, suggest little relaxation by viscous flow has occurred and instead indicate a subsurface that is less than 40% ice.
This paper presents geophysical observations of Ceres—the closest dwarf planet to the Sun, in an orbit between those of Mars and Jupiter—based on radio tracking and onboard image data acquired by the Dawn spacecraft. Gravity and shape measurements provide a key parameter that has been unobtainable through remote observations—the moment of inertia. Ceres is shown to be in hydrostatic equilibrium with an inferred normalized mean moment of inertia of 0.37. The Dawn spacecraft data and analysis reported here give the first constraints on the interior structure of a dwarf planet. Ceres emerges as a partially differentiated body, with a rocky core overlaid by a volatile-rich icy shell.
Ahuna Mons dome on Ceres formed by extrusion of a mixture of brine and solids sourced from a muddy mantle plume, according to numerical modelling of slurry rheology and a gravity anomaly found by the Dawn mission.