If and when humans establish a permanent base on the Moon, it’ll be the pits. Collapse pits, I should add. These are holes in the lunar surface where the roofs of cave-like lava tube have collapsed, allowing relatively easy access to underground “rooms” which can provide a pre-fab haven for astronauts working and living on the Moon. This idea has been around for a long time, but new research just published shows that these caves can maintain fairly mild temperatures, protected from the savage heat of sunlight during the lunar day and the brutal chill of lunar night [ link to paper ].  The basic geology here is that long ago, billions of years in the past, the Moon was pretty active volcanically . Flowing lava would carve channels into the surface — we see many of these long grooves on the Moon called rilles — and sometimes in recurrent eruptions the lava will solidify on top, creating a tube.…