Earth and Venus, being roughly the same size and distance from the sun, are often regarded as twin planets. So it is natural to wonder how the crust of Venus compares with that of our own world. Although centuries of telescopic observations from Earth could give no insight, beginning in 1990 the Magellan space probe’s orbiting radar penetrated the thick clouds that enshroud Venus and revealed its surface with stunning clarity. From the detailed images of landforms, planetary scientists can surmise the type of rock that covers Venus. It seems that our sister planet is completely covered by rocks of basaltic composition, which are very much like the dark, finegrained rocks that line the ocean basins of Earth. Magellan’s mapping, however, failed to find extensive areas comparable to Earth’s continental crust.