MAPPING A VOLCANIC WORLD: A NEW UNDERSTANDING OF SHIELD VOLCANO MORPHOLOGY AND SPATIAL RELATIONSHIPS ON VENUS

NASA’s Magellan spacecraft mapped virtually the entire Venusian surface using synthetic aperture radar (SAR) as well as nadir-directed altimetry. The SAR data collected during this mission enabled the discovery and classification of volcanic features and structures across Venus far beyond the scope of earlier missions. These data revealed a planetary surface covered in volcanic edifices of a range of sizes, as well as a surprising dearth of impact craters, consistent with large-scale volcanic resurfacing. Previous studies documented volcanic structures across the planet, but mainly focused on larger edifices, and did not have the use of recently available, stereophotogrammetry-derived topographic data. We have created a new global catalog of Venusian volcanic edifices using the Magellan SAR full-resolution radar map left- and right-look global mosaics (with ~100 meter-per-pixel (m/px) resolution). Using earlier volcano databases as a check for our mapping, we have nonetheless developed our catalog independently and at a finer spatial scale than those existing surveys. Mapping was completed in the ESRI ArcGIS environment. We recorded the latitude, longitude, and footprint (i.e., areal extent) of landforms we interpreted as volcanic on the basis of having a quasi-circular and approximately conical shape, with one side more radar-bright than the opposite side (consistent with being illuminated from a single radar-look direction). Additionally, where possible, we utilized the Magellan global altimetric topography and the stereo-derived topographic data to acquire elevation and volume measurements for a given edifice.

Our preliminary mapping results include 32,348 volcanic edifices <5 km in diameter, 1,347 edifices 5–100 km in diameter, and 88 edifices that show evidence for gravitational deformation. Furthermore, we included an additional 51,390 edifices <5 km in diameter for which only geographic coordinates were recorded, given the locally poor radar image quality. Our results so far indicate that Venus hosts far more volcanoes than previously recognized (or at least catalogued). In this presentation, we review the geographic and morphological properties of these volcanoes, and discuss the implications of this survey for our understanding of the volcanic history of Venus.