Venus

        These low-lying regions have abundant small volcanoes and long lava flows. Unlike similar plains on the Moon, Mars, and Mercury, the Venusian plains are relatively free of impact craters.

NASA's team has visited Venus. In 1962, Mariner 2 revealed that Venus has cool clouds and an extremely hot surface. Mariner 10 discovered evidence of rotating clouds.

The Soviets have successfully landed several spacecraft in the plains regions. Seven of the landers conducted chemical analyses of rocks, which indicate a composition similar to that of basaltic volcanic rocks found here on Earth. The Venera 9 lander gave us our first glimpse of the Venusian surface when, in 1975, it relayed a panoramic view of the mysterious planet. In 1981, the Venera 13 lander provided the first color images of the surface of Venus.

In the early 1990's, NASA's  spacecraft studied the rocky planet, examining the shapes of Venusian mountains, canyons and other surface features with higher resolution than has ever been seen before on a global scale. Magellan data has been used to make maps of the surface properties and the planet's interior. The planet is still geologically active in places, even though radar images of its surface indicate that little has changed in the past half-billion years.

Magellan also examined Venus' massive atmosphere of carbon dioxide and high sulfuric acid clouds.