A team of NASA-sponsored meteorite hunters has discovered what it believes is an ancient chunk of Mars — on Earth. The team of Antarctic explorers came across the 1.5-pound black rock last December while scouring for meteorites in the Transantarctic Mountains, about 466 miles from the South Pole. A subsequent analysis by the Smithsonian Institution revealed that the rock’s mineralogy and texture are “unmistakably Martian,” according to a statement released Wednesday by NASA.