TESTING CHANNEL ORIGIN HYPOTHESES IN THE MAHUEA THOLUS QUADRANGLE (V-49), VENUS

There are multiple hypotheses concerning the formation of channels on Venus’ surface. Proposed formation methods include: 1) formation via above-surface lava flows, 2) collapsed subsurface lava tubes, and 3) fluvial processes. To help test between proposed channel formation hypotheses, we have utilized Magellan synthetic aperture radar (SAR) satellite imagery (~75 m/pxl) to construct large-scale (~1:1200k) geologic maps of six channels in the V-49 quadrangle (25° to 50°S, 150-180°E) – Vishera, Matlalcue, Helmud, Umaga, Lusaber, Austrina; this region hosts the largest concentration of channels on Venus, making it an ideal location to continue testing channel formation hypotheses.

Channels in V-49 broadly trend E-W and occur along the northern and southern edges of Zhibek Planitia. The northern channel grouping includes (from west to east) Vishera, Matlalcue, and Helmud valles. These channels are <1 km wide, with lengths from 1038 to 1194 km, and sinuosity values ranging between 1.3 and 1.58. Channels in the northern group display varying gradients throughout their lengths. Vishera Vallis is first visible at approximately 300 km east of Colijnsplaat Corona. For most of its length, the channel trends parallel to a topographically high coronae flow. At 161°E 32°S, the channel trends upslope, and through this topographic high. The channel transects a relatively low section of the corona flow feature, suggesting uplift post channel formation. The southern channels are (from west to east): Umaga, Lusaber, and Austrina Vallis. They are also <1 km in width, have lengths from 425 to 844 km, and sinuosity values ranging from 1.1 to 1.6. Channels in the southern group appear to extend outwards from Mena Colles with variable gradients that slope towards the east and west. All channels in V-49 are deformed by wrinkle ridges and fractures. Given tectonic and topographic relationships, the channels appear to have formed after the corona flows and before regional long-wavelength warping. Channels have sinuosities of ~1.4, 0.4 points lower than terrestrial river sinuosities (Komatsu and Baker, 1994). Assuming V-49 channels formed by gravity driven liquid, their close proximity to volcanic features, and their tectonic/topographic relationships, suggests an origin involving surface magmatic processes.