The vehicle has been travelling through space since June. The rover will be parachuted down to Mars early in the morning in a dangerous drop.
Ed Weiler, from Nasa, said: "Mars is an incredibly difficult place to land... some call it the death planet."
The rover, called Spirit, will try to see what happened to the water on Mars, and what it was like many years ago.
It will hopefully land in the Gusev Crater, which may have once been a lake.
The rover will examine minerals and rocks to check if they hold any evidence of water.
Today, Mars is cold and dry, but it may once have had lakes, rivers and seas.
Beagle, the British made Mars probe which landed recently, has still not made contact with its controllers.
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Should we be sending probes into space?
The planet Mars
