An artist's depiction of primeval earth 3 to 4 billion years ago eerily lit by the giant early moon. Image by Karen Wehrstein

Maybe the picture above needs an update, two moons instead of one. At least that’s one explanation for some new findings which refine the Giant Impact:

The study uses new techniques and radioactive isotopes of lead and other elements to date the moon rock at 4.4 billion years old. What’s key is that this is a special type of rock that would have floated up to the moon’s crust soon after its theorized ocean of molten rock cooled. That supposedly happened soon after the moon formed as a result of a spectacular crash between Earth and a planet. The chunks that broke off formed the moon.

One possibility is the impact happened several hundred million laters than thought, another intriguing idea is that one or more moons formed which combined into the single moon we see today. That idea would be difficult to test without lots of lunar samples. But the stark differfence between the side of the moon familiar to all us as the Man in the Moon, and the far side unseen until the 1960s, does offer a that idea some preliminary support.