US space probe Spirit, which landed on Mars on 4 January, has started exploring the red planet.
It rolled down a three-metre ramp and got past a 10cm drop. Some scientists said this was a very risky move and they were glad Spirit managed it.
Charles Elachi, a Nasa scientist at the Jet Propulsion Laboratory, said: "Mars now is our sandbox, and we are ready to play and learn."
Nasa scientists hope they can find if there was once water on Mars.