Courtesy of David McKay, NASAIt weighs only 1.9 kilograms and is an estimated 4.5 billion years old. Yet the ALH84001 meteorite is probably the most argued-about rock in the universe (or at least in ...

Caption This photograph shows globules of orange-colored carbonate minerals found in the Martian meteorite dubbed ALH84001. The origin of the carbonate minerals has long puzzled scientists, but by ...