The new research, presented in the current edition of the journal Nature, postulates an enormously energetic but oblique crash between Earth and a planet the size of Mars, which is about half Earth's size.Must have been one hell of a light show. Thanks to Alindrea for the heads up.
The energy unleashed by this collision some 4.5 billion years ago would have been enough to destroy the incoming planet and melt Earth all the way through, Canup said. There would also have been some vaporized rock debris kicked up from the crash, which would start orbiting Earth.
"Once the orbiting debris cooled, it's from that stuff that the moon then coalesced," Canup said. The whole process, from collision to formation of the moon, took less than 100 years, she said — an almost inconceivably short time in planetary terms.