differ by up to 4 billion years - the vast majority of Mars' planetary existence.]]> dislodged on the inside," Schmitt said.]]> hurtling through space and surviving the searing fall through our atmosphere.]]> interpret what they see when they can't agree on how old a rock is.]]> existence.]]> impact that melts the rock down, erasing the geochemical trail.]]> intact.]]> diameter of a human hair," said study co-author Axel Schmitt, a geochemist at the University of California, Los Angeles.]]> meteorite known as Northwest Africa 5298.]]> durable little minerals.]]> Conflicting age estimates for certain rocks differ by up to 4 billion years - the vast majority of Mars' planetary existence.]]> atmosphere.]]> examine a meteorite known as Northwest Africa 5298.]]> evidence of the damage done to the meteorite by the event that may have released it from the Martian surface sometime around 22 million years ago.]]>