The moon was borne out of a cataclysmic collision, but scientists haven't been clear on the details of its violent birth. Now, in a study in the journal Science, German researchers say they've finally found clear signs in Apollo-era rock to support major theories about the moon's creation story. Most moons are either adopted or they're their planet's little siblings. But Earth's moon was sired after its ill-fated encounter with a Mars-sized protoplanet named Theia, which came barreling out of space and crashed into Earth's surface. According to many models, the newly formed moon would be 70 to 90 percent of Theia debris and the rest from Earth. Yet, the isotopic fingerprint of lunar meteorites found on Earth seemed to match closely with Earth. Was the moon more a child of Earth than of Theia? But when researchers obtained samples of three lunar rocks collected by Apollo astronauts, they found that the oxygen isotope ratios between the moon and Earth were markedly different. By discovering Theia's mark on the moon, scientists may learn more about the protoplanet destroyed in the moon's creation. Los Angeles Times