Overview

Between 1970 and 2000, solar system exploration included major missions to most of the planets. The United States sent out many unmanned spacecraft that studied the planets, their moons, and even asteroids. The Soviet Union's planetary missions included the Venera spacecraft series, some of which landed on Venus and sent back pictures from the surface. The Soviets, the Japanese, and the European Space Agency all sent probes to study Halley's Comet in 1985-86.

The space probe Mariner 10, launched November 3, 1973, was the first to travel to Mercury. (NASA. Reproduced with permission.)

Background

By 1970 humans had landed spacecraft on the moon but not on any planet. By 1999, however, spacecraft had landed on and mapped Mars and Venus, our nearest planetary neighbors. Mariner 10 visited Mercury, and the Voyager missions visited all four of the gas giant planets. The Galileo probe spent nearly four years studying Jupiter...