Revisiting the crater-based age of Cerealia Facula: High-resolution XMO7 data, measurement uncertainties, and chronological frameworks

Introduction: The bright deposits of Cerealia Facula within Occator Crater on Ceres are key indicators of recent endogenic activity, most likely linked to cryovolcanic and hydrothermal processes and the presence of subsurface brines. Constraining the absolute model age of these deposits is essential for understanding the geologic evolution of Occator and the thermal history of Ceres. Previous crater size–frequency distribution (CSFD) studies suggested Cerealia Facula is significantly younger than the Occator impact, but these were limited by small counting areas, low crater statistics, and challenges in crater detection due to complex geomorphology and significant albedo variations. The Dawn mission’s seventh, final Extended Mission Orbit (XMO7) provided the highest-resolution images of Occator, but their full scientific potential required accurate co-registration and orthorectification.

Objectives and Data: This work presents (1) a statistically robust model age for Cerealia Facula based on improved CSFD measurements, and (2) a suite of high-resolution, co-registered geospatial data products publicly available via Zenodo (doi: 10.5281/zenodo.17615400, doi: 10.5281/zenodo.14531595). Our analysis uses Dawn Framing Camera data from multiple mission phases, including XMO7 (resolutions down to ~2.7 m) and LAMO (~34 m). We combined LAMO multispectral RGB data with XMO7 clear-filter imagery, incorporating data from both FC1 and FC2 cameras to maximize spatial coverage. The resulting orthomosaics, including a pan-sharpened RGB product at 8.5 m ground sample distance, provide unprecedented spatial and spectral detail.

Methodology: Accurate image co-registration and orthorectification were achieved using a hierarchical approach, anchoring XMO7 data to a stable geodetic reference frame based on a high-resolution DTM we published early 2025. CSFD measurements were conducted across the entire facula, focusing on craters >50 m to minimize detection bias. Independent counts by multiple analysts assessed variability and robustness. Model ages were derived using both lunar-derived and asteroid-flux-derived chronology models.

Results and Implications: The new orthomosaics and DTM reveal a surface more complex than previously observed, with steep slopes, fractures, and albedo variations complicating crater identification. CSFD results confirm Cerealia Facula postdates the Occator impact, with model ages ranging from 0.4 to 39.5 Ma (most likely in the single-digit Ma range), depending on used scaling parameters during the modelling of the chronology models. These findings are supported by improved statistics and reduced detection variability. Beyond age determination, the principal outcome is the creation of a high-resolution, controlled, publicly accessible geospatial dataset (clear-filter-, pan-sharpened RGB orthomosaic and DTM) for Occator Crater, enabling future studies of cryovolcanic processes and surface modification. Furthermore, the published datasets will allow to perform detailed studies and assessments of potential future landing sites

Conclusion: This work advances our understanding of Ceres’ recent geologic activity and provides a critical baseline for future investigations, extending the scientific legacy of the Dawn mission.