(Newser) – Almost 500 million years ago in the Ordovician Period, two large bodies in the asteroid belt collided. Two asteroids, or an asteroid and a comet, blew apart and their debris and dust fell to Earth. One of these large bodies was the source of all the L-chondrite meteorites that have frequently fallen to Earth since. And the one that destroyed it? Until now, a remnant of that killer space rock has never been found. But LiveScience reports that scientists have found a strange meteorite in a Swedish limestone quarry that may be the missing "other half," the study detailing its discovery claims. For now, scientists have aptly named the rock "mysterious object." And what’s so mysterious about it? Firstly, all of the previous 100 fossil meteorites found in the quarry have been of the L-chondrite variety. This new rock is part of a group called achondrites, but its texture and exposure age make it very different.