Known for its beauty in the sky, Venus is the second planet from the Sun and similar in size to Earth. However, its immense surface heat and pressure make the planet completely uninhabitable. It has a thick, poisonous atmosphere of carbon dioxide and sulphuric acid. Thick clouds hide a surface covered with lava flows, quake faults and impact craters. In fact, one lava-filled basin is larger than the continental United States and one volcano is taller than Mt. Everest.

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 Mariners 2, 5 and 10 have all 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 colour images of the surface of Venus.

In the early 1990's, NASA's Magellan 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 sulphuric acid clouds.

Spacecraft
Launch (Mariner 2): August 27, 1962
Flyby (Mariner 2): December 14, 1962
Mass: 203 kilograms (447 pounds)
Science instruments: Microwave radiometer, infrared radiometer, flux-gate magnetometer, ion chamber and Geiger-Mueller counters, cosmic dust detector, solar plasma detector

Overview

As plans were getting under way to explore the Moon with the Rangers and Surveyors, JPL and NASA also turned their attention to the rest of the solar system. The Mariner series of missions were designed to be the first U.S. spacecraft to other planets, specifically Venus and Mars. Mariner 1 and 2 were nearly identical spacecraft developed to fly by Venus. The rocket carrying Mariner 1 went off-course during launch on July 22, 1962, and was blown up by a range safety officer about 5 minutes into flight.

A month later, Mariner 2 was launched successfully on August 27, 1962, sending it on a 3-1/2-month flight to Venus. On the way it measured for the first time the solar wind, a constant stream of charged particles flowing outward from the Sun. It also measured interplanetary dust, which turned out to be scarcer than predicted. In addition, Mariner 2 detected high-energy charged particles coming from the Sun, including several brief solar flares, as well as cosmic rays from outside the solar system.

As it flew by Venus on December 14, 1962, Mariner 2 scanned the planet with infrared and microwave radiometers, revealing that Venus has cool clouds and an extremely hot surface. (Because the bright, opaque clouds hide the planet’s surface, Mariner 2 was not outfitted with a camera.)

Mariner 2's signal was tracked until January 3, 1963. The spacecraft remains in orbit around the Sun.