DETECTION OF RECENT VOLCANISM ON VENUS USING MAGELLAN SAR DATA (Invited Presentation)

The low-lying plains covering approximately 80% of Venus are interpreted to be young based on the small and relatively unmodified superposed impact crater population. Volcanic activity is responsible for this relatively new surface. The timing, size, and distribution of recent volcanic deposits have implications for which of the endmember models, catastrophic or equilibrium resurfacing, dominated this activity on Venus. Here we analyze the extent of parabolic impact crater ejecta, interpreted as some of the youngest deposits on Venus, and their stratigraphic relationships with different terrains, such as the tesserae and low-lying plains, to search for recent volcanic activity. Measurements of the backscatter coefficient from Magellan SAR left-look data are used to determine if there is a non-uniform distribution of crater ejecta superposed on the ancient highly deformed tesserae and low-lying plains materials. At Sudenitsa Tesserae, one of our study regions, several areas of low radar backscatter are identified in tessera materials, while no areas of low backscatter are found in the adjacent low-lying plains. The most plausible source of low backscatter material is the parabolic ejecta from relatively recent impact events. There is no obvious source crater for the low backscatter material at Sudenitsa. However, the location of Sudenitsa Tesserae on the northwestern border of the Beta-Atla-Themis (BAT) region, with 2-4 times the number of volcanic features observed on the rest of the planet, may explain the absence of a source crater. For instance, recent north-trending lava flows sourced from Polik-mana Mons, to the south of Sudenitsa Tesserae, may have resurfaced the source crater and some/all of the parabolic ejecta. The presence of the low backscatter material in Sudenitsa Tesserae and a missing source crater suggests that the parent impact crater was recently resurfaced (likely less than 80 Ma). A low-eruption rate lava flow sourced from the BAT region is capable of burying the source crater and some or all of the parabolic ejecta on the low-lying plains, consistent with equilibrium resurfacing models.