This picture shows a cutaway view of the possible internal structure of Venus. The image was created from Mariner 10 images used for the outer atmospheric layer. The surface was taken from Magellan radar images. The interior characteristics of Venus are inferred from gravity field and magnetic field measurements by Magellan and prior spacecraft. The crust is shown as adark red, the mantle as a lighter orange-red, and the core yellow. What is known about the Venusian interior comes primarily from the Venera, Pioneer Venus and Magellan spacecraft. Before these explorers, scientists thought that Venus would have tectonic processes similar to that of Earth's mantle convection. Venus and Earth are both similar in size and presumable the same composition. However, Venus showed no sign of plate tectonism, and appears to have a single plate which makes it very different from Earth.