CONSTRAINTS on THE SURFACE EVOLUTION OF VENUS GLEANED FROM MULTIPLE DATASETS: IS CATASTROPHIC RESURFACING VIABLE?

NASA’s Magellan mission two decades ago revealed that Venus lacks plate-tectonics processes, yet Venus’ surface evolution and operating geodynamic system remain elusive. It is widely accepted that global-scale catastrophic melt resurfacing played a major role in shaping Venus’ surface. This simplistic view emerged from early (1994) Monte Carlo models aimed at explaining why ~1000 impact craters ≤270 km diameter show near-random spatial distribution and why most craters appear pristine. However, subsequent modeling by several groups clearly shows that a wide range of surface histories can account for these crater observations, and that catastrophic resurfacing is neither a necessary nor unique solution. Further, recent independent studies show that additional crater characteristics, and local and regional geologic relations, are difficult, or impossible, to reconcile with catastrophic resurfacing.

A variety of geologic and surface modeling studies provide robust constraints for surface evolution hypotheses. These studies include: a) Monte Carlo crater modeling; b) impact crater characteristics, evolution and relative ages; c) ancient ribbon-tessera terrain character, distribution, and history; d) radial dike swarm characteristics, global distribution, and temporal constraints; e) global and regional wrinkle ridge patterns, and the relative ages of wrinkle ridge suites; f) the age of volcanic plains units relative to adjacent features; g) the nature and distribution of shield terrain; h) the surface expression and evolution of Artemis, a monstrous circular feature with two concentric troughs (2400 and >5000 km diameter), a radial dike swarm (12,000 km diameter), and concentric wrinkle ridges (13,000 km diameter); i) the characteristics and relative ages of crustal plateaus and volcanic rises; and j) constraints derived from geologic mapping of numerous VMap regions (~7.5x10⁶ km² each) by independent workers, which eliminates the need for a singular resurfacing event.