Venus is about the same size as Earth, but a very different planet. It rotates in a backward direction, a characteristic it shares with Uranus. Venus is nearer the Sun than Earth and has a very thick atmosphere, the surface temperature is extremely high, as much as 475° Celsius (900° Fahrenheit).
The planets closest to the Sun—Mars, Earth, Venus, and Mercury—are made mostly of rock. The rocky planets all formed in our inner solar system. Their geological history is preserved on their surfaces. Their landscapes reveal the processes that shaped them: impacts, crustal movements, volcanic activity, and erosion. Gravity, temperature, air, and water all play leading roles in their geological stories.
Characteristics of Venus
Planets and moons across our solar system bear the scars of collisions. Impact craters form on their surfaces when a dust particle, rock, asteroid, or comet smashes into them. Impact craters come in all sizes and shapes, depending on the impacting object size, impact angle, and surface into which the object crashes.
The surface of Venus is extremely hot. When an impact creates a crater, some of the ejecta is hot and fluid. Flows of this molten material, called impact melt, can extend for long distances, as shown by this radar image of Addams crater (54 miles/ 87 kilometers across).
Venus has a very thick, hot, carbon dioxide atmosphere. Its surface pressure is more than 90 times that of Earth’s. Winds in the upper atmosphere of Venus travel 110–220 mph (180 – 360 km/h).
An atmosphere can slow down an incoming object or melt it completely. The atmosphere of Venus is so dense that some objects break apart and form clustered impact craters, like those seen in this image.
Rocky worlds can also reshape themselves from internal forces that push and pull at their crustal materials, a process called tectonics. Compressional forces shove crustal material together to create ridges and mountains. Extensional forces stretch and pull the crust apart to form fault scarps, canyons, and valleys. While impacts are sudden, tectonic forces operate over long periods of time. The landforms they create can take millions of years to form.
Earth has globalized plate tectonics. Venus does not. This is thought to be because of how hot and dry the planet is. Instead, tectonics operate regionally, rather than through plates that span the entire globe like Earth.This image shows elevation on Venus, with blue and purple colors being the lowest elevations, and greens, yellows, and oranges being areas of higher elevation.
Like Earth, volcanism also plays a role on Venus. Venus has a hot interior core surrounded by hot mantles. One way these rocky worlds release interior heat is through volcanic activity. This can involve molten rock, or magma, being forced into the crust. As the interior cools, it shrinks, causing the crust to wrinkle like the skin of an apple as the core dries and shrivels over time. Volcanism creates a variety of landforms, not just volcanoes, depending on the properties of the lava (such as viscosity and composition) and on the planetary environment (like gravity and presence of an atmosphere).
Venus displays the greatest diversity of volcanic features among the rocky worlds. Over 80% of Venus is covered by relatively young volcanic plains, less than 500 million years old. The abundance of these plains suggests that Venus may have experienced catastrophic volcanic events that caused lava to flood large parts of its surface.