Well, it could be a bit of dimension hopping. Or aliens abducting the whole moon. A wormhole opening. A time machine. An new Philadelphia experiment. An interstellar object entering the solar system, passing Earth and capturing the moon by gravit - but here the problem would be why it would vary its speed and meet so many solar system at the same time. An ancient race having established a galaxy-wide transportation system.
Hm, think we already had all that in some series, didn't we...
But any scenario - combined with that all Earth gets destroyed and the moonbase crew is the last group of homo sapiens in the universe!
With the moon traveling into a huge black hole at the centre of the galaxy - ouch ...!
Well, I already like this new series right now ! ! !
