Iván López

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We present a 1:10M scale map of the Niobe Map Area (NMA) of Venus (0N-57N/60E-80E). Geologic mapping employed NASA Magellan synthetic aperture radar and altimetry data. The NMA geologic map, and its companion Aphrodite Map Area (AMA), cover ~25% of Venus’ surface, providing with an important and unique perspective to study global and regional geologic processes. Both areas display a regional coherence of preserved geologic patterns that record three sequential geologic eras: the ancient era, the Artemis superstructure era, and the youngest fracture zone era. The NMA preserves a limited record of the fracture zone era, contrary to the AMA. However, the NMA host a diverse and rich assemblage of material and structures of the ancient era, and structures that define the Artemis superstructure era, with a footprint covering more than 25 percent of the surface of Venus. These two eras likely overlap in time and account for the formation of basement materials and lower plain units. Impact craters formed throughout the NMA recorded history. Approximately 40% of the impact craters show interior flood deposits, indicating that a significant number of NMA impact craters experienced notable geological events after impact crater formation. This and other geologic relations record a geohistory inconsistent with postulated global catastrophic resurfacing. Together, the NMA and the AMA record a rich geologic history of the surface of Venus that provide a framework to formulate new working hypotheses of Venus evolution, an to plan future studies of the planet.

Vicki L Hansen

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We present a 1:10M scale geologic map of the Aphrodite Map area (AMA) of Venus (0N-57S /60E-80E). Geologic mapping employed NASA Magellan synthetic aperture radar and altimetry data. The AMA geologic map, with detailed structural elements and geologic units covering over one eighth of Venus’ surface, affords an important and unique perspective to test models of global scale geologic processes through time. Geologic relations record a history inconsistent with global catastrophic resurfacing. The AMA displays a regional coherence of preserved geologic patterns that record three sequential geologic eras: the ancient era, the Artemis superstructure era, and the youngest fracture zone era. The ancient era and Artemis superstructure, with a footprint covering more than 25 percent of the surface, are recorded in the Niobe map area to the north. The latter two eras likely overlap in time. The fracture zone domain, part of a globally extensive province, marks the most spatially focused tectonomagmatic domain within the AMA. Impact craters are both cut by, and overprint, fracture zone structures. Twelve percent of AMA impact craters that occur within the fracture zone domain predate or formed during fracture zone development. This observation indicates the relative youth of the fracture zone era and is consistent with the possibility that this domain remains geologically active. The AMA records a rich geologic history of large tract of the surface of Venus and provides an important framework to formulate new working hypotheses of Venus evolution, and contribute to planning future studies of the surface of planets.