Hesperia Planum is a broad lava plain in the southern highlands of the planet Mars. The plain is notable for its moderate number of impact craters and abundant wrinkle ridges. It is also the location of the ancient volcano Tyrrhena Mons. The Hesperian time period on Mars is named after Hesperia Planum.
Viking MDIM of Mare Tyrrhenum quadrangle. Hesperia is the intermediate-toned (dusky) region (left of center) lying between the darker regions Mare Tyrrhenum (left) and Mare Cimmerium (right).
Closeup of the surface of northwestern Hesperia Planum, as seen by HiRISE camera on Mars Reconnaissance Orbiter (MRO).
Viking orbiter view of wrinkle ridges in Hesperia Planum. North is at upper left. Image is about 107 km (66 mi) across.
THEMIS daytime IR mosaic image of Tyrrhenus Mons. This ancient, eroded volcano was nicknamed the Dandelion when first seen in Mariner 9 images.
The Hesperian is a geologic system and time period on the planet Mars characterized by widespread volcanic activity and catastrophic flooding that carved immense outflow channels across the surface. The Hesperian is an intermediate and transitional period of Martian history. During the Hesperian, Mars changed from the wetter and perhaps warmer world of the Noachian to the dry, cold, and dusty planet seen today. The absolute age of the Hesperian Period is uncertain. The beginning of the period followed the end of the Late Heavy Bombardment and probably corresponds to the start of the lunar Late Imbrian period, around 3700 million years ago (Mya). The end of the Hesperian Period is much more uncertain and could range anywhere from 3200 to 2000 Mya, with 3000 Mya being frequently cited. The Hesperian Period is roughly coincident with the Earth's early Archean Eon.
HiRISE image illustrating superpositioning, a principle that lets geologists determine the relative ages of surface units. The dark-toned lava flow overlies (is younger than) the light-toned, more heavily cratered terrain at right. The ejecta of the crater at center overlies both units, indicating that the crater is the youngest feature in the image. (See cross section, above right.)
Geologic contact of Noachian and Hesperian Systems. Hesperian ridged plains (Hr) embay and overlie older Noachian cratered plateau materials (Npl). The ridged plains partially bury many of the old Noachian-aged craters. Image is THEMIS IR mosaic, based on similar Viking photo shown in Tanaka et al. (1992), Fig. 1a, p. 352.
Viking orbiter view of Hesperian-aged surface in Terra Meridiani. The small impact craters date back to the Hesperian Period and appear crisp despite their great age. This image indicates that erosion on Mars has been very slow since the end of the Noachian. Image is 17 km across and based on Carr, 1996, p. 134, Fig. 6-8.
