Mapping the Distribution and Global Budget of Impact-Derived Sediment on Venus

Abstract:

The high temperatures (740K) of the Venus surface prohibit fluvial processes. Therefore the sediment on Venus’ surface is the product of impact cratering. This sediment is deposited in parabola-shaped ejecta blankets carried westward by high altitude winds. The thickest and assumed newest deposits for 49 of the ~900 Venus craters are visible in Magellan SAR (S-band) data. With time, the sediments from these ejecta deposits are distributed across the Venus surface by surface winds; however, aeolian deposits such as dunes are rare on Venus, corresponding to ~3 x 10⁴ km³ [Schaller and Melosh, Icarus, 1998]. The total volume of sediment on the surface of Venus is not well constrained. Here we use ArcGIS to map thickness and volume contours of crater ejecta deposits assuming all craters produce a parabola-shaped deposit at the time of formation [after method of Basilevsky et al., JGR, 2004] and calculate the cumulative volume of impact-derived sediment present on the surface of Venus over the average crater retention age of 500 million years. We estimate the planet’s total budget of sediment to be a minimum of 2.9 x 10⁵ km³, suggesting that 10⁵ km³ of sediment is not accounted for by the aeolian deposits observed. This preliminary estimate yields a sediment accumulation rate of 5.8 x 10⁵ m³/year, or 1.2 nm/year assuming a 500 Ma surface age. This is 3 orders of magnitude larger than a global estimate of 0.01 nm/year of sediment production via erosion on Mars during the Amazonian [Golombek and Bridges, JGR, 2000]. With the composite volume maps, we have also identified regions where sediment is most concentrated, many of which are associated with observed venusian aeolian features (i.e. Mead Crater yardang field, Stowe Crater dune field). The calculated sediment budget and the cumulative volume map presented here are used to identify locations that may host additional aeolian features on the surface of the planet, such as the regions around the craters Greenaway and Isabella. This mapping shows that 44% of Venus has never been directly covered by an impact crater deposit and thus may be relatively sediment starved. This work is a step towards further constraining the nature of aeolian processes and sediment cycling on Venus.