https://www.theguardian.com/science/2017/oct/19/lunar-cave-discovery-raises-hopes-for-human-colonisation-of-moon Some of us have virtually delved the depths of the Moon in "Destiny", but I'd like to use this announcement to encourage CIG to expand the surface modular habitats as just the tip of the iceberg of potentially massive underground settlements. With this announcement, even under VERY heavy and continuing surface meteor bombardment, lava tube originated caves are likely a common planetary feature. Think of Olympus Mons! It is probably like Swiss cheese at many depths.