When you think about a habitable colony on the moon, says The Economist, you probably imagine “gleaming domes or shiny metallic tubes”. The problem is that to keep out solar radiation, the walls would need to be metres thick. It’d be “more like a hobbit hole than Moonbase Alpha”. But scientists have another solution: setting up a base inside the “giant geological tunnels” just below the lunar surface. These lava tubes, a legacy of when the moon had volcanoes, are hundreds of times bigger than the ones we have on Earth – “colossal cave systems that are up to a kilometre across and hundreds of kilometres long”.
The idea wouldn’t be to stick a moon base inside a lava tube – it would be to pressurise a whole section of the tube with breathable air, so that residents could live and work “with no need for space suits”. Researchers have calculated that this could be done safely, without risking collapse. They also reckon the ends of the tunnels could be sealed with a version of the inflatable membranes already used for flood prevention in tunnels on Earth. The one big flaw? You’d have to “prepare humanity for a return to life in caves”.