Only after the impact did oceans of molten rock cool so Earth and moon could fully develop internal layers. Carsten Munker of the University of Munster said Earth s core probably started forming soon after the solar system s 50 millionth birthday. Then a planet-sized object hit Earth, which still might have been covered by an ocean of magma, or molten rock. Impact debris was hurled into orbit around Earth, and a portion of the fragments consolidated to form the moon, which was so hot a magma ocean covered it. Then, Earth and moon cooled, with the moon developing a core, overlying mantle and uppermost crust, while Earth also completed its core, mantle and crust, Munker said.
Impacts capture people s imaginations.
A spectacular collision is more exciting than the Earth just rotating around and capturing a moon somehow. He suspected they were tidal rocks. He said the new study proved it by showing how the pinstripe sediment patterns coincided with daily, twice-monthly and monthly tidal cycles. Just as today, rising flood tides deposited light-colored, sandy layers on shallow coastal sea floors and estuaries. When waters went slack, fine silt and clay particles formed thinner dark, muddy layers.