Life on the moon is the next step for us humanoids, given that we've all but destroyed our home planet, and it turns out that we may yet become underground mole people. 

A new analysis of the moon that comes courtesy of NASA's GRAIL spacecraft suggests that there could be some pretty huge craters or lava tubes underneath the surface of our lunar neighbour, and that they're absolutely massive. 

According to a conference paper from the folks at Purdue University, we're not talking about Ailwee Caves big either, we're talking about craters big enough to house entire cities, as illustrated by this handy little graph that shows what it would look like to sneak the entire city of Philadelphia into one of those bad boys. 

Pic via Purdue University/courtesy of David Blair

Theoretically, at least, the possibility of having an underground city up there is a real one, as the "gravity is much lower on the moon and lunar rock doesn't have to withstand the same weathering and erosion", meaning that they would be structurally sound. Living underground on the moon, if that is where we end up in the sci-fi future that we all envisage, is also a better idea than living on the surface, as the caverns provide "possible habitation sites safe from cosmic radiation and micrometeorite impacts".

All this living beneath the surface of the moon carry on sounding familiar? That's because it's the plot of Iron Sky, pretty much, except when we get to the moon we hope that there won't be any Nazis there.