Mars Shuttle Possible in 2018? AP

Though it will likely be decades before a human sets foot on the Martian surface, former astronaut Buzz Aldrin and scientists at Purdue University already are working on a shuttle they hope will one day take people from Earth to the Red Planet and back. The interstellar bus line would involve two massive spacecraft that could house up to 50 people on their six-month shuttles between the two planets. The craft would continuously cycle between Earth and Mars using gravity as their primary power source, with an occasional shot from a booster rocket. “If we’re going to go to Mars with human beings, we need to do it in an evolutionary way, so that we can continue doing it,” said Aldrin, the second man to walk on the moon.