Impact craters, terrain type, and terrain ages

Impact craters, terrain type, and terrain ages

. Impact craters (top diagram) are randomly scattered all over Venus. Most are pristine (white dots). Those modified by lava (red dots) or by faults (triangles) are concentrated in places such as Aphrodite Terra. Areas with a low density of craters (blue background) are often located in highlands. Higher crater densities (yellow background) are usually found in the lowland plains. The terrain type (middle diagram) is predominnanately volcanic plains (blue). Within the plains are deformed areas such as tessarae (pink) and rift zones (white), as well as volcanic features such as coronae (peach), lava floods (red) and volcanoes of various sizes (orange). Volcanoes are not concentrated in chains as they are on Earth, indicting that plate tectonics does not operate. Terrain age data (bottom diagram) indicate that volcanoes and coronae tend to clump along equatorial rift zones, which are younger (blue) than the rest of the Venusian surface (green). Tesserae, ridges and plains are older (yellow). In genreal, however, the surface lacks the extreme variation in age that is found on Earth and Mars.

Copyright 2010, Professor Kenneth R. Lang, Tufts University