The Magellan spacecraft obtained radar images of over 98% of the surface of Venus throughout its very successful mission. Here an entire hemisphere of the planet can be seen, as if the radar images allowed Magellan to peel back the dense, obscuring atmosphere. Bright linear features are relatively rough terrain associated with faulting and folding in mountain-belt areas. Dark areas are lowland plains that reflect very little radar signal back to the spacecraft, most likely resulting from a relatively smooth surface at scales greater than the 12-centimeter wavelength of the radar system. Data from subsequent orbits filled in some of the gaps present in this image (bottom), generated shortly after Magellan completed its first mapping cycle.
Magellan mosaic (Press Release P-39225).