A Global Characterization of the Gravity Signatures of Coronae on Venus

Introduction: Coronae are quasi-circular to circular volcano-tectonic features unique to Venus among the terrestrial planets. They were first identified in Venera 15/16 images [1], and their tectonic, volcanic, and topographic characteristics have been classified in detail using Magellan SAR image and topography data [2, 3]. Several studies of gravity signatures associated with coronae have been conducted in an attempt to constrain models for corona formation and evolution [4-7]. We report here the results of a global survey of corona gravity signatures, using a newly expanded corona data base [3]. Our study is motivated by recent investigations [3, 810] indicating that individual coronae have had long and complex histories and that coronae as a class have been forming over a significant fraction of the period for which there is a surface record of Venus’ geological history (~ 750 Myr) [11]. In addition these investigations suggest that coronae may have contributed significantly to plains volcanism. Through a global analysis of gravity signatures associated with coronae we identify those coronae that we infer to be comparatively young, on the basis of positive gravity anomalies attributable to support by some combination of mantle dynamics and flexure of a strong lithosphere. We identify a second class of coronae that we infer to be older, on the grounds that their topography is compensated and their free-air gravity anomaly is near zero. These two classes have distinct spatial distributions. We discuss the implications of our findings in the context of corona evolution, the resurfacing history of Venus, and the relationship of coronae to large-scale Venus mantle dynamics [12].