http://www.universetoday.com/128208/buried-lave-tubes/Marius Hills pit
Artist concept of the GRAIL mission, twin spacecraft that fly in tandem around the Moon to measure its gravity field. Credit: NASA/JPL
Artist’s impression of a lava tube measuring several kms wide, with the city of Philadelphia shown inside for scale: Purdue University/David Blair
科學家認為 直接蓋在洞內比較快
還能抗宇宙射線
月面重力圖
地球上的
https://en.wikipedia.org/wiki/Lava_tube