We present a state-of-the-art map (1:2,000,000) of the entire Hellas basin floor based on USGS mapping standards.

Via crater-based model ages, stratigraphic analyses, and previous investigations of rim areas, we compiled a detailed, self-consistent geologic history for the entire basin.

Phreatomagmatic activity around Hellas basin ∼3.7 Ga ago likely caused intense dissection along rim and deposition of interior formation.

Low-energy fluvial environments occurred along northern rim. No landforms indicating standing body of ice or water in basin are preserved.

Honeycomb terrain possibly canopy of truncated upwelling structures formed before lower wrinkle-ridged plains.

Banded terrain appears to be thin veneer occurring along wind-carved trough in eastern basin.