How have we explored the Solar System?

Before the telescope, people explored the sky with their eyes. They saw how the planets seemed to wander through the sky. They learned to predict where the Sun, the moon, and planets would be in the sky. They built some observatories -- places for watching the sky. They watched the Sun and stars to tell the time of year. In China, they even knew when the moon would block the Sun. Most people thought that celestial bodies could cause war or peace on Earth.

After telescopes were first made, people kept making them better. Astronomers saw that planets are not like stars. They are worlds, like the Earth. They could see that some planets have moons.They began to think about what these worlds were like. At first, some thought that the other planets and moons had people or animals living on them. They thought about how it would be to live on these other worlds. Then they made telescopes better and saw that there are no plants or animals on the Moon or on Mars.


Twelve Astronauts walked on the Moon about 35 years ago. They brought rocks and dirt back to Earth.Spacecraft flew by Venus, Mars, and the outer planets. The pictures they took showed us a lot of what we know about these worlds.Robots landed on Mars in 1971, 1976, and 1997. They took thousands of pictures of the planets. Two robots, "Spirit" and "Opportunity", are working on Mars right now. They send photos and movies back to Earth. They also check rocks to find out what the rocks are made of.

So far, we have not found any life except on Earth. Maybe tiny one-celled life once lived on Mars. Maybe there is life under the ice on Jupiter's moon Europa. New spacecraft are being planned to look for life on these worlds.