Lunar Lava TubesLava tubes are sub-surface volcanic tunnels. These structures form on surfaces slopi

Lunar Lava TubesLava tubes are sub-surface volcanic tunnels. These structures form on surfaces sloping 0.4-6.5 degrees when a roof of basaltic lava (up to 40m thick) hardens over molten rock below. This molten rock eventually drains away leaving a hollow structure. These structures also form on Earth as seen in Iceland, Portugal, Spain and the USA, however it is thought they would be larger on the moon due to its lower gravity.This picture shows a 50km chain of collapse tunnels moving into an un-collapsed example of a lunar lava tube. In 2008 the Japanese spacecraft Kaguya sent back a picture of a suspected opening to a lava tube from the Marius Hills region (a noted lunar volcanic province). This structure was circular and approximately 65m in diameter and estimated to be 85m deep. Surrounding the hole on the lunar surface was a thin lava sheet which may have protected the tube from collapsing previously due to impacts. From 2009 onwards NASA’s Lunar Reconnaissance Orbiter also sent back pictures of deep caverns on the moon which had potential to be collapsed lava tubes.It is thought that lava tubes would offer an environment to build a base for humans on the moon due to the protection they would offer. There would be three major factors such a tube would protect a human base from. Firstly caverns with roofs thicker than 10m would create a more stable temperature (of about -20 degrees C) than is found on the lunar surface, which varies by 100s of degrees C in a day. Secondly the moon also has no atmosphere, so these tubes would provide protection from cosmic radiation. Finally protection from meteorites, micrometeorites and collision ejecta would be offered (however it should be noted that stable lava tubes could be disrupted by seismic events and meteorite strikes).It has been structurally modelled that tubes would be stable when sized between 1 and 5km wide and therefore could host a pre-fabricated base. The building of this base in the tube would be beneficial as lightweight construction material could be used as it would not have to shield the base from the threats mentioned above.~SAPictures: http://bit.ly/1MRgf85By NASA/GSFC/Arizona State University and http://bit.ly/1H6pWRNBy Melissausburn -- source link

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