267°E in the Arcadia quadrangle (MC-3) between the large volcano Alba Mons and the Tempe Terra plateau.

[2] It is likely an ancient watercourse that formed during the early Hesperian (or late Noachian) period,[3] around 3.7 billion years ago.

[5] The International Astronomical Union (IAU) formally adopted the name Enipeus Vallis in 1991.

[3] This northern valley segment gradually loses its identity amid the narrow grabens of Tantalus Fossae.

[3] Faint longitudinal striations and streamlined erosional bedforms are common all along the floor of the valley.

[17] Enipeus Vallis is located at the western edge of the Tempe Terra plateau in the Tempe-Mareotis region.

[3] The region lies on a broad topographic shelf bounded by the higher elevations of Alba Mons to the west and Tempe Terra to the east.

[21][22] The region is transected by numerous northeast-trending grabens that form parts of the Tempe, Mareotis, and Tantalus Fossae; these are fracture systems of varying ages that are oriented radially from the Tharsis bulge.

The region west of Enipeus Vallis is characterized by Hesperian-aged volcanic flows from Alba Mons.

[3] At the end of the Noachian period, these highland materials underwent an episode of fluvial erosion and resurfacing.