2007 GSA Denver Annual Meeting (28–31 October 2007)

Paper No. 2
Presentation Time: 1:45 PM


BJONNES, Emily E., CGGVeritas, 10300 Town Park Dr, Houston, TX 77072, HANSEN, Vicki L., Department of Geological Sciences, University of Minnesota Duluth, Duluth, MN 55812, SWENSON, John B., Department of Earth & Environmental Sciences, University of Minnesota Duluth, 1114 Kirby Dr, Duluth, MN 55812 and MACLIN, Richard F., Department of Computer Sciences, University of Minnesota Duluth, Duluth, MN 55812, Emily.Bjonnes@cggveritas.com

Venus' impact crater character and distribution are widely interpreted as evidence that Venus experienced near-global catastrophic resurfacing over 10-100 m.y., ~0.5-1 Ga. Although there is no direct evidence for catastrophic resurfacing, workers favor catastrophic resurfacing due to Monte Carlo modeling of equilibrium resurfacing aimed at reproducing the near-random distribution of impact craters (A) and the low number of modified craters (B) (Strom et al. 1994). Previous tests of equilibrium resurfacing analyzed resurfacing across 50-10%, and 0.03-0.001% of the surface; 50-10% resurfacing met criteria B, but not A, whereas 0.03-0.001% met criteria A, but not B. We conducted new Monte Carlo modeling of resurfacing across 5-0.1% resurfacing areas. We assumed average crater diameter, d=30 km, and a region of crater modification 2d around circular resurfaced regions. Each experiment, which included 1000 runs, specified a random portion of the surface to cover per resurfacing event with 100% of the planet resurfaced, and ~1000 final impact craters; modified craters and crater distribution were analyzed for each run. Crater spatial distribution was analyzed following the method by Turcotte et al. (1999) by quantifying the deviation distances between craters to a fitted sine curve. Preliminary results indicate that 5% resurfacing meets criteria B, but not A; 0.1% resurfacing meets criteria A, but not B; 1.0 and 0.7% resurfacing meet both criteria A and B. Thus these results indicate that, to a first-order, equilibrium resurfacing is equally viable to catastrophic resurfacing, based on crater constraints. Furthermore, the plausible areas (1-0.7%) are similar to the area of individual crustal plateaus, thus Spatially Isolated Time-Transgressive Equilibrium Resurfacing (SPITTER hypothesis) meets constraints imposed by impact crater distribution and character. Work continues to determine the sensitivity of parameters including timing of resurfacing events, impact crater flux, and length of the experiment. These results indicate that catastrophic resurfacing of Venus is not required by crater distribution or character, and that equilibrium resurfacing of areas of 1-0.7% is equally viable.