Fredrik Bruhn, the CEO of Ångström Aerospace Corporation has designed a better more mobile rover for mars. Unlike other rovers this one almost never gets stuck has fewer motors and never flips over! "The beauty of the system is it needs very little energy to go around rocks, so unless you're landing on a surface that looks like a bed of nails, it should be fine," Bruhn says. Bruhn says he can make four mars balls for as little as 6 milion!
http://www.cnn.com/2008/TECH/space/10/13/eod.mars.balls/index.html