Implications from stereo‐derived topography of Venusian impact craters

Abstract

inverse gravity trend observed for the terrestrial planets, and they are --50% deeper than current estimates for complex craters on the Earth. Unlike the other terrestrial planets, neither terrain-floor depths nor central structure heights increase with increasing crater diameter. An interesting trend for which we have no explanation is that on Venus, the Moon, Mars, and Ganymede, central peaks generally rise to within a constant elevation relative to the surrounding terrain, but that elevation is lower on the Moon and Mars than on Venus and Ganymede.

Resurfacing on Venus

“…The equilibrium resurfacing produces modified craters in the range 90-182 (140.5 + 30.38, 20 uncertainties). Both results are in good agreement with the estimates of the number of modified craters of Venus provided by Herrick et al (1997) and Herrick and Sharpton (2000), 85-129, and Wichman (1999), 57-123. The equilibrium resurfacing is in contradiction with the very low number of modified craters estimated by Schaber et al (1992), 56 andCollins et al (1999), 29-56.…”

“…This value is imposed by the observation that 40% of the area is covered by young units in the study of the frequency-area distribution performed by Romeo and Turcotte (2009). This moderate magmatic activity can account for the higher number of modified craters estimated by Herrick and Sharpton (2000) and Wichman (1999). Therefore, our catastrophic model is quite different from the proposed catastrophic evolution of Strom et al (1994), where only 4-6% of the planet has been volcanically resurfaced since the last global resurfacing event.…”

“…The updated version (third release) of the crater database initially published by Herrick et al (1997) estimates the number of craters modified by volcanism to be between 85 and 129, while Wichman (1999) estimates this value to be between 57 and 123 (6-13% of the crater population). These higher numbers of modified craters provided new support to equilibrium steady-state resurfacing evolutions (Herrick and Sharpton, 2000;Stofan et al, 2005). In contrast, the analysis of craters modified by volcanism performed by Collins et al (1999) provide that they are in the range 29-56, favoring a catastrophic scenario with a very limited volcanic activity since the global resurfacing event.…”

“…The ejecta diameter is calculated using the continuous ejecta average extent power-laws for craters bigger and smaller than 20 km derived from the crater population by Herrick et al (1997). The crater rim height is obtained from the power law relation deduced for bright-floored craters, which are considered to be pristine, calculated by Herrick and Sharpton (2000). The total number of craters generated is an indication of the duration of the models.…”

“…Detailed studies of the process of crater modification (Herrick and Sharpton, 2000;Wichman, 1999) revealed that the amount of craters partially covered by lava flows is higher than the initial estimation of 56 modified craters of Schaber et al (1992). The updated version (third release) of the crater database initially published by Herrick et al (1997) estimates the number of craters modified by volcanism to be between 85 and 129, while Wichman (1999) estimates this value to be between 57 and 123 (6-13% of the crater population).…”