Thursday, Mitt Romney sent a press release to supporters mocking competitor Newt Gingrich's proposal to build a U.S. colony on the moon. Friday, fellow Republican candidate Rick Santorum joined the fun, releasing a satellite radio ad that quotes Gingrich's space plans. "Reckless spending has led to a 15 trillion dollar national debt ... And what does Newt Gingrich suggest? Spending half a trillion dollars on a moon colony," the ad says.