It’s been 20 years since the first Earthling vehicle touched down on the Red Planet. The Sojourner wasn’t much bigger than a toy—just a foot high and a couple feet wide—and definitely not big enough to host humans. Putting people on the surface of Mars will take a much bigger set of wheels. One prototype for the job stops by Atlanta this weekend, July 14-16. You can see it at SunTrust Park, the first stop on the Kennedy Space Center's Summer of Mars tour.