A conceptual model for the Hesperian Deuteronilus ocean, its regression and formation of the oceanic deposits of the Zhurong Member of VBF at the Zhurong landing site. (a) Schematic stratigraphic column of the Zhurong landing site in Utopia Planitia and proximity to the interpreted shoreline. The –3600 m contour in (b) and (c) represents the boundary of the Vastitas Borealis Formation (VBF), a smooth lowland unit consisting of sedimentary deposits of a possible ancient oceanic water body before 3.6 Ga [18,20]. After that, ocean regression may have resulted in a shallow marine environment near the current position of the Zhurong rover (c), which is indicated by the sedimentary structures of the Zhurong Member rocks shown in Figs 2 and 3 and Supplementary Figs S6–S8.