A group of scientists says a December meteorite over Sri Lanka held "fossilized biological structures"—but many of their colleagues aren't convinced. According to the pro-fossil team, electronic microscope images show tiny pieces of algae known as diatoms, supporting the idea of "panspermia." The theory—developed in part by one of the scientists involved—holds that asteroids distribute biological matter while on the move. The scientists say their discovery is among the biggest in centuries, NPR reports.
But other experts have suggested that the meteorite may simply have been contaminated. It's also possible "that the fireball was of terrestrial origin," notes MIT's Technology Review; indeed, the Meteoritical Society doesn't have a record of the Sri Lanka meteorite. Another explanation: The material inside may not be biological at all. But the group behind the finding is standing its ground. "The highly intricate and woven patterns on the outer shells of diatoms are impossible to generate by any other process than biology," says one. "The cosmic ancestry of humans becomes ever more securely established."