Internal crater modification on Venus: Recognizing crater‐centered volcanism by changes in floor morphometry and floor brightness

Abstract

Abstract. Bright-floored and dark-floored craters on Venus show systematic differences in their size, distribution and apparent modification. Bright-floored craters exhibit the following characteristics: an interior radar brightness comparable to the youngest craters on Venus, a tendency toward smaller crater diameters, and a broad range of crater elevations. In contrast, the dark-floored craters are darker than pristine craters on Venus, are typically much larger, and preferentially occur at lower elevations. They also have larger floors than pristine craters of the same size and are similar in many respects to floor-fractured craters on Venus. Of the four proposed origins for dark crater floors, these observations are most consistent with crater-centered volcanism. Surface weathering or eolian deposition may contribute to floor darkening in some cases, but neither of these mechanisms, nor impact melts, can independently explain the full range of observed modifications.

Resurfacing on Venus

“…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.…”

“…Modified catastrophic resurfacing is in good agreement with the concentration of modified craters observed in the BAT anomaly area, while equilibrium resurfacing produces more modified craters out of the BAT anomaly. The larger numbers of craters modified by volcanic flooding found by Wichman (1999) and Herrick and Sharpton (2000) can be produced by a moderate volcanism covering 40% of the planetary surface from the last global resurfacing event following a moderated decay of the volcanic activity. Therefore, our catastrophic resurfacing model differs from previously proposed catastrophic evolutions (Schaber et al, 1992;Strom et al, 1994;Collins et al, 1999), where the volcanic activity after the global resurfacing event was very restricted.…”

“…""third release updated database of Herrick et al (1997). and *** Wichman (1999) are shown for comparison.…”

“…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).…”

“…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).…”