Here's an interesting article on the first 'skylight' - opening to a possible underground lava tube or cavern - discovered on the Moon: http://www.newscientist.com/article/dn18030-found-first-skylight-on-the-moon.html I'm wondering how it might be possible to map out underground caverns and lava tubes on the Moon, without having to look for openings. Shouldn't there be a way to use cavern-sensing radar, or something like that, to spot underground cavities from an orbiting satellite or from a surface rover? What's the most accurate way to map such underground cavities, without having to rely on chance discovery of openings? What's the best sensory/instrumentation for this purpose? My understanding is that to scan through rock, you need to use very low frequency radio waves at high power, but their long wavelengths would limit the resolution of the features being scanned for. Here's a recent article I read about hyperlensing - could this be the answer? http://www.physorg.com/news175702307.html Perhaps this could be a useful approach to mapping out underground cavities with high precision. Could hyperlensing be useful for planetary exploration and underground mapping? What do you all think?