###### meteorites arrive in pretty ###### shape. They get toasted ###### they fall through the ######. Still, these meteorites provide ###### lot of information to ######, whose job it is ###### study rocks. But it ###### be hard for geologists ###### make sense of what ###### see when they can't ###### on how old a ###### is. And when it ###### to certain rocks, scientists ###### by as much as ###### billion years.
Mars itself ###### much older than 4 ###### years. So the question is: Do these rocks tell the beginning, or the end, of Mars' story?
Recently, a team ###### scientists tried to answer ###### question for one group ###### meteorites.]]> To settle the question, ###### examined a meteorite known ###### Northwest Africa 5298. They ###### at very tiny deposits ###### it called baddeleyites. These ######, zirconium-rich minerals are "10 ###### smaller than the diameter ###### a human hair," said ###### Axel Schmitt.

A Tiny Rock Might Have The Answer

To figure ###### how old a rock ######, scientists measure certain radioactive ###### inside it. But if ###### big crash or explosion ###### the rock down, that ###### gets erased.
That's why ###### picked the tiny baddeleyites: ###### are hard little minerals. ###### not easy to melt ###### down. By looking at ###### radioactive uranium and lead ###### this tough rock, the ###### found that it formed ###### around 187 million years ######. This proved that the ###### were young.]]>