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An aqueously altered carbon-rich Ceres


The surface mineralogy of dwarf planet Ceres appears to be dominated by products of rock–fluid interactions, such as phyllosilicates—some of which are NH4-bearing—and carbonates1,2,3. Elemental concentrations derived from the inferred mineral mixing fractions, however, do not match measurements of H, C, K and Fe on Ceres4. A complicating factor in assessing Ceres’s unique surface composition is the secular accretion of asteroids typical of chondritic compositions. Here we show that Ceres’s mineral and elemental data can be explained by the presence of carbonaceous chondritic-like materials (~50–60 vol%), possibly due to infalling asteroids, admixed with aqueously altered endogenic materials that contain higher-than-chondritic concentrations of carbon. We find that Ceres’s surface may contain up to 20 wt% of carbon, which is more than five times higher than in carbonaceous chondrites. The coexistence of phyllosilicates, magnetite, carbonates and a high carbon content implies rock–water alteration played an important role in promoting widespread carbon chemistry. These findings unveil pathways for the synthesis of organic matter, with implications for their transport across the Solar System.

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Fig. 1: Ceres’s post-formation collisional history.
Fig. 2: Spectral models of Ceres.
Fig. 3: Ceres’s upper crust.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


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This work was supported by the NASA Dawn project. We thank H. Y. McSween, B. L. Ehlmann, M. Villarreal and S. Protopapa for their insightful comments.

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S.M. conceived the work. A.R., M.C.D.S., E.A., M.C., H.K. and E.P. provided spectral models. T.H.P. and N.Y. provided elemental models. All authors contributed to the interpretation of the results and to the writing of the manuscript.

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Correspondence to S. Marchi.

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Supplementary Tables 1–3, Supplementary Figures 1–3

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Marchi, S., Raponi, A., Prettyman, T.H. et al. An aqueously altered carbon-rich Ceres. Nat Astron 3, 140–145 (2019).

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