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Post-impact cryo-hydrologic formation of small mounds and hills in Ceres’s Occator crater


The intimate mixture of ice and silicate within the uppermost few kilometres of Ceres influences its geology and the evolution of its subsurface. Both ground ice and cryovolcanic processes have been hypothesized to form geologic terrains on Ceres, including within Occator crater, where they have been suggested to influence the post-impact surface evolution. Both types of processes involve the presence and expression of volatiles and brines, such that distinguishing between them could be difficult. Here, we use images and topography data from the NASA Dawn mission to investigate the morphology, age and distribution of mounds and hills within Occator crater, and infer their origin. The shapes and relative ages of many of these features suggest that they formed as impact-induced water-rich flows that covered the crater floor refroze in a manner similar to the formation of periglacial ice-cored mounds on Earth called pingos. We suggest that impacts on Ceres produced hydrologic conditions for surface changes in the absence of cryovolcanic processes. Our findings imply that cryo-hydrologic processes extend beyond Earth and Mars, and have been active on Ceres in the geologically recent past.

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Fig. 1: Comparison of Cerealia Tholus with pingos on Earth.
Fig. 2: Physical characteristics of small mounds in Occator crater.
Fig. 3: Map of small mounds and materials in Occator crater.
Fig. 4: Two of the best examples of pristine conical and depressed summit mounds in Occator bear strong resemblance to arctic pingos.

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Data availability

All Dawn imaging and topographic data are available online through the NASA Planetary Data System at, with the search terms “Ceres regional DTMs and mosaics for selected regions”, “Occator”, “Dawn Ceres FC2 calibrated” and “XMO7”. Measurements and interpretations for each feature evaluated are available in Supplementary Table 1.


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This research was carried out under funding from the Dawn mission. Dawn was operated by the Jet Propulsion Laboratory for NASA. We thank the Dawn Flight Team at NASA’s Jet Propulsion Laboratory for the development, cruise, orbital insertion and operations of the Dawn spacecraft at Ceres. We thank the instrument teams at the Max Planck Institute, German Aerospace Center (DLR), Italian National Institute for Astrophysics (INAF) and Planetary Science Institute (PSI) for the acquisition and processing of Dawn data.

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Authors and Affiliations



B.E.S. led the conceptual development, analyses, interpretation of the data and preparation of the manuscript. H.G.S. helped with the conceptual development and edited the paper. K.H.G.H. contributed additional analyses and figures and assisted in data interpretation and editing. K.H.G.H., J.E.C.S., K.D.D. and V.N.R. undertook geologic mapping. K.U. contributed a figure and discussion of terrestrial analogues. P.M.S., D.L.B., D.A.W., J.C.C.-R., A.N., C.A.R. and C.T.R. contributed to interpretation of the data and preparation of the manuscript.

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Correspondence to B. E. Schmidt.

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Peer review information Primary Handling Editor: Stefan Lachowycz.

Supplementary information

Supplementary Information

Supplementary Figs. 1–7, Tables 2 and 3, discussion and references, with the footnote for Supplementary Table 1.

Supplementary Table 1

Locations, measurements and characterization data for each of the mounds studied.

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Schmidt, B.E., Sizemore, H.G., Hughson, K.H.G. et al. Post-impact cryo-hydrologic formation of small mounds and hills in Ceres’s Occator crater. Nat. Geosci. 13, 605–610 (2020).

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