From our small world we have gazed upon the cosmic ocean for untold
thousands of years. Ancient astronomers observed points of light
that appeared to move among the stars. They called these objects
planets, meaning wanderers, and named them after Roman deities --
Jupiter, king of the gods; Mars, the god of war; Mercury, messenger
of the gods; Venus, the god of love and beauty, and Saturn, father
of Jupiter and god of agriculture. The stargazers also observed
comets with sparkling tails, and meteors or shooting stars apparently
falling from the sky.
Science flourished during the European Renaissance. Fundamental
physical laws governing planetary motion were discovered, and the
orbits of the planets around the Sun were calculated. In the 17th
century, astronomers pointed a new device called the telescope at
the heavens and made startling discoveries.
But the years since 1959 have amounted to a golden age of solar
system exploration. Advancements in rocketry after World War II
enabled our machines to break the grip of Earth's gravity and travel
to the Moon and to other planets.
The United States has sent automated spacecraft, then human-crewed
expeditions, to explore the Moon. Our automated machines have orbited
and landed on Venus and Mars, explored the Sun's environment, observed
comets, and asteroids, and made close-range surveys while flying
past Mercury, Jupiter, Saturn, Uranus and Neptune.
These travelers brought a quantum leap in our knowledge and understanding
of the solar system. Through the electronic sight and other "senses"
of our automated spacecraft, color and complexion have been given
to worlds that for centuries appeared to Earth-bound eyes as fuzzy
disks or indistinct points of light. And dozens of previously unknown
objects have been discovered.
Future historians will likely view these pioneering flights through
the solar system as some of the most remarkable achievements of
the 20th century.