Abstract
ABSTRACT We present a 1:2,500,000 geological map of the Alpha Regio (V-32) quadrangle, Venus. The V-32 quadrangle extends from 0° to 25 S, 0°to 30° E with an area of approximately 7,600,000 km2. Geological mapping was conducted using full resolution (maximum 75 m/pixel) SAR, altimetry and stereo-derived topography data from NASA's Magellan mission in ArcGIS 10.5. Nearly 40,000 lineaments were mapped. The oldest unit, tessera terrain, is present in two major regions: Alpha Regio and Minu-Anni Tessera. Two major fracture belts, both oriented approximately NNW-SSE, and four minor fracture belts have been identified and characterized. Two previously unrecognized wrinkle ridge trends of radiating and circumferential orientation have also been identified in the northeastern corner of the quadrangle. A total of 77 geological units were mapped. Plains material, previously mapped as global regional plains units, was divided into 27 units. Earlier estimates of the diameters of several coronae have been extended by hundreds of kilometres.
Highlights
Radar technology is required to image the surface of Venus as the thick and opaque Venusian atmosphere shrouds the surface from visible light
Detailed geological mapping of graben-fissure systems by Ernst, Desnoyers, Head, and Grosfils (2003) at a scale of 1:250,000 in the Beta Regio and Guinevere Planitia regions of Venus identified five times as many systems than were previously identified from mapping conducted at larger scales
The V-32 quadrangle records a history of polyphase contractional deformation, with at least three separate generations. This mapping study represents the first detailed geological map produced for the Alpha Regio (V-32) quadrangle, and one of few maps of areas on Venus to be produced at a scale of 1:2,500,000
Summary
Venus is Earth’s closest neighbour, and shares similarities to Earth in size (85.7% of Earth volume), mass (81.5% of Earth mass), and composition (Colin, 1983). Features on Venus are relatively well preserved, as the lack of water and low surface wind speed (0.3–1.0 m/s) produce little erosion (Phillips & Hansen, 1991). Deformed terrains such as fold belts, plains with wrinkle ridges, fracture belts, rift zones, and topographically elevated, deformed regions (known as tesserae) are present on Venus (Basilevsky & Head, 2000a; Basilevsky & Head, 2003; Ivanov & Head, 1996; Phillips & Hansen, 1991). The first mapping cycle had the radar antenna positioned in a left-looking sense and captured SAR images covering 83.7% of Venus’ surface. The three mapping cycles brought the total coverage of SAR images to 98.3% of Venus’ surface, at a maximum resolution of 75 m/pixel
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