Nice story from Reuters on Russian plans to colonize lunar lava caves. They would likely provide significant shielding from the sleet of solar radiation that pummels these airless (or nearly airless) bodies. All explorers need do is seal them up with a skylight, and they’re good to colonize.
The Universe Today site had a post on lunar caves last year. Above is an oblique view (image credit: NASA/GSFC/Arizona State University) in the Marius Hills, which would likely have been an Apollo 18, 19 or 20 landing site had the program not halted with the 17th mission. Wouldn’t that have been amazing for 1973? Discovering a lava cave on the moon.
H. G. Wells wrote all about it over a century ago. We should’ve been listening to him, though I doubt we’ll find lunar life in those caves. Probably a lot of very fascinating geology.
When I was a boy, I loved this film adaptation.
Getting back to the caves, it might be fascinating to explore these. Possible that water (or ice) might be found in the depths of the moon. A lunar base, let alone a colony, would be a massive undertaking. But finding resources in the caves that could sustain human life would be a big plus.