Geologic Map of the Niobe Planitia Region (I-2467), Venus.

Abstract

We present a 1:10M scale geologic map of the Niobe Planitia region of Venus (0°N-57°N/ 60°E-180°E). We herein refer to this area as the Niobe Map Area (NMA). 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 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 hosts a diverse and rich assemblage of material and structures of the ancient era and structures that define the Artemis superstructure era. 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 and to plan future studies of the planet.

Geologic Map of Aphrodite Map Area (AMA; I‐2476), Venus

“…In summary, the most first‐order observation that emerges from the AMA is the regional coherence of preserved geologic patterns, which provide a variable record of three relatively distinct geologic eras: the ancient era, the Artemis superstructure era, and the youngest fracture zone complex era. The first two eras are also variably recorded within the NMA (Hansen & López, 2018; López & Hansen, 2020a, 2020b); all three eras can be extrapolated to the global scale, although the Artemis era is not strictly global as the Artemis superstructure covers about 30% of the planet surface (Hansen, 2018). Geologic relations captured within the AMA illustrate the spatial and temporal relations of these three eras across time and space as described herein.…”

“…The lineaments, which are more widely spaced as compared to other portions of the fracture zone, become more difficult to delineate, due in part to the tessera‐terrain host and its characteristic ribbon‐tessera terrain fabric. A possible north‐trending zone anchored by Rosmerta Corona in the south may also form part of a fracture zone, although this zone lies mostly to the north outside the AMA and is characterized by coronae rather than fractures or other lineaments (Hansen & López, 2018; López & Hansen, 2020a, 2020b).…”

“…The picture that emerges is one in which tectonism (deformation) and magmatic activity became spatially more focused with time. Initially, the Artemis superplume resulted in uplift of a huge circumferential region coupled with formation of radial fractures with a footprint of at least 12,000‐km diameter extending north into the NMA (Hansen & López, 2018; Hansen & Olive, 2010; López & Hansen, 2020a). Locally, magma emerged from these radial fractures forming unit Afu.…”

“…In this contribution we present a geologic map of the Aphrodite Map Area (AMA) ( I‐2476 ; 0°N–57°S/60–180°E). A geologic map of the Niobe Planitia Map sheet ( I‐2467 ; 0–57°N/60–180°E referred to herein as Niobe Map Area [NMA]), adjacent to the AMA but north of the equator, is presented in a separate contribution (López & Hansen, 2020a, 2020b). Geologic mapping of the AMA and NMA were undertaken in a collaborative project.…”