Cratering on Ceres: Implications for its crust and evolution

Hiesinger, H.; Marchi, S.; Schmedemann, N.; Schenk, P.; Pasckert, J. H.; Neesemann, A.; O’Brien, D. P.; Kneissl, T.; Ermakov, A.; Fu, R. R.; Bland, M. T.; Nathues, A.; Platz, Thomas; Williams, D. A.; Jaumann, R.; Castillo‐Rogez, Julie; Ruesch, O.; Schmidt, B. E.; Park, R.S.; Preusker, Frank; Buczkowski, D. L.; Russell, C. T.; Raymond, C. A.

doi:10.1126/science.aaf4759

Cited by 147 publications

(209 citation statements)

References 64 publications

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“…Comparisons of d/D for Ceres' largest craters to finite element simulations of viscous relaxation indicated that most had experienced negligible relaxation (Bland et al, ) and suggested that Ceres was less ice‐rich than anticipated. At the same time, morphological analysis indicated that the transition from simple to complex craters on Ceres occurred at a d/D consistent with icy Saturnian satellites and inconsistent with rocky bodies (Hiesinger et al, ). Together, these two lines of analysis indicated that Ceres' crust (roughly Ceres' outer 40 km; Fu et al, ) is composed of a material that behaved like ice on short timescales/high strain rates and like rock on long timescales/low strain rates.…”

Section: Resultsmentioning

confidence: 99%

A Global Inventory of Ice‐Related Morphological Features on Dwarf Planet Ceres: Implications for the Evolution and Current State of the Cryosphere

et al. 2019

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We present a comprehensive global catalog of the geomorphological features with clear or potential relevance to subsurface ice identified during the Dawn spacecraft's primary and first extended missions at Ceres. We define eight broad feature classes and describe analyses supporting their genetic links to subsurface ice. These classes include relaxed craters; central pit craters; large domes; small mounds; lobate landslides and ejecta; pitted materials; depressions and scarps; and fractures, grooves, and channels. Features in all classes are widely distributed on the dwarf planet, consistent with multiple lines of observational evidence that ice is a key component of Ceres' crust. Independent analyses of multiple feature types suggest rheological and compositional layering may be common in the upper ~10 km of the crust. Clustering of features indicates that ice concentration is heterogeneous on nearly all length scales, from ~1 km to hundreds of kilometers. Impacts are likely the key driver of heterogeneity, causing progressive devolatilization of the low latitude and midlatitude crust on billion‐year timescales but also producing localized enhancements in near surface ice content via excavation of deep ice‐rich material and possible facilitation of cryomagmatic and cryovolcanic activity. Impacts and landslides may be the dominant mechanism for ice loss on modern Ceres. Our analysis suggests specific locations where future high‐resolution imaging can be used to probe (1) current volatile loss rates and (2) the history of putative cryomagmatic and cryovolcanic features. The Cerean cryosphere and its unique morphology promise to be a rich subject of ongoing research for years to come.

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Section: Resultsmentioning

confidence: 99%

A Global Inventory of Ice‐Related Morphological Features on Dwarf Planet Ceres: Implications for the Evolution and Current State of the Cryosphere

et al. 2019

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“…This feature does not correlate with the color ratio composite maps (Williams et al, ) nor with maps of spectral features (McCord & Zambon, ). However, this feature broadly corresponds to a zone of low crater density (Hiesinger et al, ).…”

Section: Resultsmentioning

confidence: 99%

“…Smooth circumcrater areas correspond to ejecta blankets covering preexisting heavily cratered terrains. The areas of subdued circumcrater roughness were previously identified as low‐crater‐density areas in Hiesinger et al (). This behavior is notably different from that of lunar, Martian, and Mercurian crater ejecta.…”

Section: Discussionmentioning

confidence: 99%

Surface Roughness and Gravitational Slope Distributions of Vesta and Ceres

et al. 2019

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Heavily cratered terrains dominate the surfaces of asteroid 4 Vesta and dwarf planet 1 Ceres. The data from the Dawn spacecraft allowed reconstruction of high‐resolution shape models of these bodies. We used the stereophotoclinometric shape models to compute gravitational slopes and topographic roughness of Vesta and Ceres. We compute the slope distributions of Vesta and Ceres and compare them to those of the other bodies with heavily cratered terrains. The distribution of slopes of Vesta and Ceres has a kink at ≈34°. The slope distribution is steeper for slopes higher than ≈34°. The Moon and Mars have a similar kink but at a lower (shallower) slope (≈29°–30°). We hypothesize that this kink corresponds to the angle of repose, which is higher on the two minor bodies compared to that of Mars and the Moon. We have also analyzed the topographic roughness of Vesta and Ceres. Vesta's topography is characterized by lower roughness in the southern hemisphere that was resurfaced by giant impacts. The roughness of Ceres is mostly controlled by regional‐scale geology with no significant large‐scale variations. Large, fresh craters have smooth ejecta blankets on both Vesta and Ceres unlike previously observed rough ejecta on the Moon, Mars, and Mercury. On Ceres, the smooth ejecta craters also have smooth floors explained by impact slurry. Lineaments of elevated roughness are abundant on Ceres, whereas are nearly absent on Vesta. The roughness maps we produced provide a synoptic view of the surface texture and could be used to aid geologic mapping.

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“…We have previously used the asteroid‐derived cratering rate, which relies on current best knowledge of the asteroid size‐frequency distribution and collision rates (e.g., Bottke et al, ; Marchi et al, ). Another model describing the impact cratering rate on Ceres is the lunar‐derived model (LDM), which takes the known crater chronology for the Moon and extrapolates it to Ceres (Hiesinger et al, ).…”

Section: Resultsmentioning

confidence: 99%

Water Vapor Contribution to Ceres' Exosphere From Observed Surface Ice and Postulated Ice‐Exposing Impacts

et al. 2019

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Telescopic observations have detected an exosphere around Ceres, composed of either water vapor or its photolytic products. Proposed mechanisms for its formation include sublimation or sputtering from solar energetic particles of buried ice, surface ice, or an optically thin seasonal polar cap. We estimate the amount of water vapor produced by known exposures of water ice, detected in Dawn spacecraft image and spectral data and by ice exposures from subresolution impact craters. We use thermal and sublimation modeling to take into account slope, orientation, and, in the case of water ice within craters, shadowing due to crater walls. We use a Monte Carlo approach to calculate the number of ice‐exposing impacts, where they occur on Ceres' surface, and how long the ice within the impact crater remains bright (e.g., less than one monolayer of sublimation lag). We find that the observed water ice patches on Ceres could account for ~0.06 kg/s of water vapor to (with Oxo crater as the main contributor) and that ice‐exposing impacts that remain bright in appearance after one Ceres year supply 0.08–0.56 kg/s of vapor, depending on the regolith volume fraction of the ice. While water ice has not been detected to date at Occator crater, if it were present we find that Occator is unlikely to be a major contributor of vapor. We find a typical background water vapor production rate from all of Ceres, combining surface and buried ice, of about a few tenths of a kilogram per second.

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Cratering on Ceres: Implications for its crust and evolution

Cited by 147 publications

References 64 publications

A Global Inventory of Ice‐Related Morphological Features on Dwarf Planet Ceres: Implications for the Evolution and Current State of the Cryosphere

A Global Inventory of Ice‐Related Morphological Features on Dwarf Planet Ceres: Implications for the Evolution and Current State of the Cryosphere

Surface Roughness and Gravitational Slope Distributions of Vesta and Ceres

Water Vapor Contribution to Ceres' Exosphere From Observed Surface Ice and Postulated Ice‐Exposing Impacts

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