Correlation of Venus Surface Features and Geoid

Abstract

The distributions of pairs of features on Venus are compared using simple statistical tests. We consider coronae types, crater types, and chasmata; some of these are obviously associated, and some are possibly associated. Coronae are grouped to represent evolutionary stages, tectonic and volcanic modification of craters is considered, and the chasmata are represented by five great circle arcs. These arcs fit rift or extension zones at the 90% level, totaling 55,000 km, comparable to the length of spreading ridges on Earth. Comparing these sets with Venus' geoid field, we find that all the chasmata correlate positively with geoid highs and negatively with lows, with the peaks in the geoid field occurring at the intersections of the arcs. Modified craters also exhibit this relation to the geoid. The domal coronae, the youngest and currently active, may be sites of upwelling. These correlate strongly with geoid highs and negatively with geoid lows, whereas later-stage coronae, the majority, do not show this correlation. Strong association of the youngest coronae with Themis–Atla suggests that the most recent activity occurs along this arc.