Right now, two rovers are on planet Mars. The robots are the size of golf carts. They landed on Mars six years ago.
The Mars Exploration Rovers are named Spirt and Opportunity. Scientists thought the robots would only work for 90 days. Both of them still roam the red planet. They explore Mars and relay information to scientists. To learn more about the robots, go to http://marsrovers.jpl.nasa.gov/home/index.html
NASA wants to learn as much as they can about Mars before they send astronauts to visit the planet. You can help. And you don't even need to leave earth!
NASA needs for you to send them a rock. Scientists will use a special tool to learn about your rock. The tool they use is just like the one on the Mars rovers Spirit and Opportunity. They will be able to find out if your rock is like a rock on Mars.
To learn more about joining "Rock Around the World," go to http://ratw.asu.edu/program.html. You might want to ask a teacher or parent to help you.
If you have trouble choosing a rock, check out one of my favorite books. It is written by Byrd Baylor and is called Everybody Needs a Rock.