Loughborough University ran a robotics class project to build a Mars explorer out of Legos Mindstorm.

Their site documents the entire project, gives complete parts lists and design constraints, and gives Legos style pictures adding a few blocks at a time as building instructions.

The home page is http://www.lboro.ac.uk/departments/el/robotics/MarsEx/home.htm

From there go to the archives page and follow the entire process of defining and procuring a project "bid". Then fulfill the mission. Or just skip to the building instructions. It uses some non-Lego parts.