Volcanology of Venus
The surface of Venus is dominated by volcanic features and has more volcanoes than any other planet in the Solar System. It has a surface that is 90% basalt, and about 65% of the planet consists of a mosaic of volcanic lava plains, indicating that volcanism played a major role in shaping its surface. There are more than 1,000 volcanic structures and possible periodic resurfacing of Venus by floods of lava. The planet may have had a major global resurfacing event about 500 million years ago, from what scientists can tell from the density of impact craters on the surface. Venus has an atmosphere rich in carbon dioxide, with a density that is 90 times greater than Earth's atmosphere.
Atmosphere of Venus
Due to the lack of the intrinsic magnetic field on Venus, the solar wind penetrates relatively deep into the planetary exosphere and causes substantial atmosphere loss. The loss happens mainly via the magnetotail. Currently the main ion types being lost are O, H and He. The ratio of hydrogen to oxygen losses is around 2 (i.e. almost stoichiometric) indicating the ongoing loss of water.