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We used Mars Express High Resolution Stereo Camera images of the Tyrrhena Patera volcano to assign cratering model ages to material units defined in the VikingOrbiter‐based geologic mapping. Cratering model ages are generally consistent with their stratigraphy. We can identify three key intervals of major activity at Tyrrhena Patera: (1) formation of the volcanic edifice in the Noachian Period, ∼3.7–4.0 Ga, shortly following the Hellas impact (∼4 Ga) and coincident with the formation of Hadriaca Patera (∼3.9 Ga); (2) modification of the edifice and formation of the caldera rille and channels in the Hesperian Period, possibly extending into the Amazonian Period; and (3) a final stage of modification in the Late Amazonian Epoch, ∼0.8–1.4 Ga. Early‐ to mid‐Hesperian activity on Tyrrhena Patera is consistent with similar activity on Hadriaca Patera at ∼3.3–3.7 Ga. The most recent dateable event on Tyrrhena Patera is modification on the upper shield, caldera rille, and channel floors at ∼800 Ma. This coincidence of resurfacing in three units suggests a widespread process(es), which we speculate involved preferential (aeolian?) erosion of small craters on these flatter surfaces relative to the other units on the volcano. Alternatively, some combination of pyroclastic flow emplacement on the upper shield and fluvial activity in the caldera rille and channels, followed by differential aeolian erosion and deposition, could have produced the present surface. Regardless, major geologic resurfacing ended at Tyrrhena Patera nearly a billion years ago.

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New high-resolution datasets have prompted a mapping-based study of the 2500-km-long Echus Chasma and Kasei Valles system that utilizes geomorphic details, stratigraphic relations, and cratering statistics derived from the new datasets. Our results suggest that between the Hesperian and Amazonian Epochs on Mars (3.7 Ga to Recent) the study area was affected by at least 4 episodes of widespread volcanic activity and 4 periods of episodic fluvio-glacial activity. This paper discusses the Noachian to Hesperian (N2.6 Ga) history of the study area, during which time in the Hesperian three of the volcanic episodes took place along with the first two episodes of fluvioglacial activity. Highlights of our new findings and refinements from this time period include (1) two ancient western floods sourced from Tharsis that occurred around 3.61 and 3.4 Ga and carved the east-trending path of north Kasei Valles; (2) Uranius Dorsum with 58 aligned cones along its length that was emplaced in north Kasei around 3.6 Ga between these periods of early flooding; (3) possible ash deposits surrounding Echus Chasma, one of which contains narrow dendritic valley systems that may have been carved over a period of about 10,000 yr; and (4) evidence that suggests glaciers and near-surface ice may have contributed to erosion of local units.

A seamless mosaic has been constructed including a 3D terrain model at 50 m grid-spacing and a corresponding terrain-corrected orthoimage at 12.5 m using a novel approach applied to ESA Mars Express High Resolution Stereo Camera orbital (HRSC) images of Mars. This method consists of blending and harmonising 3D models and normalising reflectance to a global albedo map. Eleven HRSC image sets were processed to Digital Terrain Models (DTM) based on an opensource stereo photogrammetric package called CASP-GO and merged with 71 published DTMs from the HRSC team. In order to achieve high quality and complete DTM coverage, a new method was developed to combine data derived from different stereo matching approaches to achieve a uniform outcome. This new approach was developed for high-accuracy data fusion of different DTMs at dissimilar grid-spacing and provenance which employs joint 3D and image co-registration, and B-spline fitting against the global Mars Orbiter Laser Altimeter (MOLA) standard reference. Each HRSC strip is normalised against a global albedo map to ensure that the very different lighting conditions could be corrected and resulting in a tiled set of seamless mosaics. The final 3D terrain model is compared against the MOLA height reference and the results shown of this intercomparison both in altitude and planum. Visualisation and access mechanisms to the final open access products are described.