Is it aliens? Here's why it's hard to know for sure.

Meteorite hunters scouring Antarctica on snowmobiles discovered something ancient along a stretch of the cold and rocky Allan Hills in 1984 that would later surprise the world. A team of scientists [INS: announced :INS] 12 years later that the 4-pound Martian meteorite that landed there around 13,000 years ago could be Earth's...