A new test that produced methane under conditions mimicking the deep interiors of Earth and Mars lends support to an idea that the gas could theoretically support unseen colonies of microbes on both worlds. And the study hints at the possibility of a potential vast supply of petroleum products. While the lab work doesn’t reveal what’s really down there, it has nudged a controversial theory about what’s under our feet one step closer to the mainstream. The research was led by Henry Scott of Indiana University at South Bend and was published online last week by the National Academy of Sciences.