The mysterious far side of the moon has long excited astronomers and science fiction writers alike because it never faces the Earth.
But scientists now believe the moon may have faced the other way, before an asteroid flipped it around billions of years ago. A study of impact craters suggests that our satellite performed the ultimate about-turn. Dr Mark Wieczorek and Matthieu Le Feuvre, from the Paris Institute of Earth Physics, studied the age and distribution of 46 known craters. Because it faces the direction of orbiting travel, the moon's western hemisphere should have more impact craters than its eastern hemisphere. The French scientists found this was true of young craters, but older craters were mostly concentrated in the east. The implication was that the eastern face had once experienced more bombardment than the western face.
'This could be explained if a large asteroid impact had set the moon turning,' the New Scientist magazine reported. 'Such an impact would have put the satellite's rotation rate out of whack, so that for tens of thousands of years it would have appeared to slowly turn as viewed from Earth. Eventually, it would have settled into the current position.'