Venus is the second planet from the Sun. As the brightest natural object in Earth's night sky after the Moon, Venus can cast shadows and can be, on rare occasion, visible to the naked eye in broad daylight. Venus lies within Earth's orbit, and so never appears to venture far from the Sun, either setting in the west just after dusk or rising in the east a little while before dawn. Venus orbits the Sun every 224.7 Earth days. Venus does not have any moons, a distinction it shares only with Mercury among the planets in the Solar System.
Internal Structure: The similarity in size and density between Venus and Earth suggests they share a similar internal structure: a core, mantle, and crust. The slightly smaller size of Venus means pressures are 24% lower in its deep interior than Earth's. The principal difference between the two planets is the lack of evidence for plate tectonics on Venus, possibly because its crust is too strong to subduct without water to make it less viscous. This results in reduced heat loss from the planet, preventing it from cooling and providing a likely explanation for its lack of an internally generated magnetic field.
Surface: The surface of Venus is dominated by geologic features that include volcanoes, large impact craters, and aeolian erosion and sedimentation landforms. Venus has a topography reflecting its single, strong crustal plate, with a unimodal elevation distribution (over 90% of the surface lies within an elevation of -1.0 and 2.5 km) that preserves geologic structures for long periods of time.
Magnetic Field: The lack of an intrinsic magnetic field at Venus was surprising, given that it is similar to Earth in size and was expected also to contain a dynamo at its core. A dynamo requires three things: a conducting liquid, rotation, and convection. The core is thought to be electrically conductive and, although its rotation is often thought to be too slow, simulations show it is adequate to produce a dynamo. On Venus, a global resurfacing event may have shut down plate tectonics and led to a reduced heat flux through the crust. This would cause the mantle temperature to increase, thereby reducing the heat flux out of the core. As a result, no internal geodynamo is available to drive a magnetic field. Instead, the heat from the core is reheating the crust.