Pioneer 10 and Pioneer 11 were the first spacecraft to travel to a planet more distant than
Mars. They were launched one year apart, in 1972 and 1973. They both flew by Jupiter, and
Pioneer 11 went on to Saturn.
There were many serious questions about navigating a spacecraft past Mars. Could it safely
make its way through the thousands of asteroids between Mars and Jupiter? How strong would
Jupiter's radiation be -- would it disable or destroy the spacecraft? Pioneer 10 and 11 traveled
safely through the asteroid belt and survived Jupiter's intense radiation.
They showed us we could explore the mysterious outer planets of our solar system. The two
spacecraft paved the way for the Voyager missions launched just a few years later, in 1977.
Next: The Voyager and Ulysses Missions 
