Posted by tourdemars to Meteorites at July 5, 2003 12:00 PM

Six years ago, Ben Weiss spent all night slicing the oldest rock on Earth into pieces the size of a child's fingernail. The precious slivers of dark brown meteorite offered Weiss, then a first-year Caltech graduate student, a chance to delve into the most hotly contested debate in geology: whether a potato-size piece of Mars blasted from the red planet 15 million years ago carried remnants of Martian life to Earth.