Haulani crater on the dwarf planet Ceres

Posted by Dr. Katrin Krohn, German Aerospace Center, Institute of Planetary Research

Haulani is one of the most prominent features on Ceres. The impact crater has bright interior and extensive ejecta with farranging crater rays of about 160 km to 490 km. Haulani shows an overall smooth bright crater floor with flow features and some cracks in the floor’s northwestern part, parallel to the impact crater rim. This crater exhibits a hummocky elongated mountainous ridge in the central part of the crater with flows running downslope the ridge crest ponding toward mass-wasting deposits of the rim. Pits occur on the crater floor and in parts of Haulani’s ejecta. Since Ceres shows evidence of a volatile-rich crust, the pits are likely due to rapid post-impact outgassing of hydrated salts or ground ice.

figure1_haulani_color

Image 1: Color mosaic of Haulani, showing the diverse morphology of the crater.

Image 1 shows Haulani crater with enhanced colors. The flanks of the Haulani impact structure exhibit three different types of lobate materials, forming lobate flows with well-defined margins, smooth fine-grained material distributes on all lobate facies. The flows appear to have been diverted around solid blocks during their emplacement, as well as to have partly incised the crater flanks. These smooth flows are interpreted to be a mixture of impact melt and cryovolcanic flows. Haulani impact may have hit an unstable ice-rich subsurface layer. A discharge of this layer by the impact may have caused subsidence of the surface material and, therefore, the formation of depressions, cracks and the failure of the western part of the crater rim of Haulani. An inhomogeneous distribution of the ice-rich subsurface layer may result in a reasonably intact impact crater with failure structures.

figure2_haulani_dtm

Image 2: DTM of Haulani, showing the elevation differences within and around the crater.

Image 2 shows that the Haulani impact crater was formed on a north-south topographical transition with a higher elevation in the east and a lower elevation in the west. Materials extend into the lower plain from the collapsed western part of the crater rim. The fracturing of the inner crater rim resulted in the formation of a stepwise sliding of material, which resulted in a slight terracing.

Further Reading

Bland, M.T. , et al. (2016), Composition and structure of the shallow subsurface of Ceres revealed by crater morphology. Nature Geoscience 9, 538–542 .

Buczkowski, D.L. , et al.  (2016), The geomorphology of Ceres. Science 353, 6303 .

De Sanctis, M. C., et al. (2015), Ammoniated phyllosilicates with a likely outer Solar System origin on (1) Ceres, Nature, 528, 241-244.

De Sanctis, M.C. , et al. (2016), Bright carbonate deposits as evidence of aqueous al- teration on (1) Ceres. Nature 536, 54–57 .

Krohn, K. et al. (2016), Cryogenic flow features on Ceres: Implications for crater-related cryovolcanism, Geophysical Research Letters, 43, 1-10.

Krohn, K. et al. (2018), The unique geomorphology and structural geology of the Haulani crater of dwarf planet Ceres, Icarus 316, 84-98.

Neumann, W. et al. (2015), Modelling the internal structure of Ceres: Coupling of accretion with compaction by creep and implications for the water-rock differentiation. Astronomy and Anstrophysics 584, A117.

Sizemore et al. (2017), Pitted terrains on (1) Ceres and implications for shallow subsurface volatile distribution. Geophysical Research Letters, 44, 6570-6578.

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