Indian scientists analysing data from the Chandrayaan-1 lunar orbiter have identified geological features on the moon which may provide a perfect location for a future moon base.

Any manned base on the Moon is exposed to very harsh conditions: Extreme variations of temperature, high levels of radiation from the Sun, cosmic rays and gamma radiation from distant high-energy astronomical objects, and the constant bombardment of micrometeorites present considerable health and safety challenges.  The simplest solution is to build the entire base underground and let several meters of lunar rock serve as a natural shield.  But if excavating large tunnels or caverns is a costly and dangerous job on Earth, it is almost impossible on the Moon, where workers would need clumsy space suits with limited supplies of food, water and oxygen.  The goal is to find some sort of natural cavern and start construction inside.

Recent high-resolution images of the Moon’s surface have revealed the occasional collapsed lava tubes.  Lava tubes form when a thick heavy flow of molten rock, in the form of lava, begins cooling.  The outer exposed surface of the flow hardens and crystallises into solid rock, while the liquid core continues to flow.  Sometimes the flow stops before it has cooled all the way through and the molten lava drains out of the tube, leaving only a hollow structure.  Suitable tubes are very difficult to find on the Moon, however — they remain hidden underground until something causes the roof to collapse.  Such a collapse fills the tube with rubble and leaves it exposed to open space, rendering it unsuitable for human habitation.

But now, buried in the 70,000 images returned by Chandrayaan-1 before the mission ended, a set of stereoscopic photos have shown what appears to be a tube which has only partially collapsed (left).  Looking at the picture, we see two collapsed tubes aligned with each other, and an empty space between them.  It seems likely that these two collapsed tubes were part of one longer tube, and the area between them represents a section which has not collapsed.  We should not get too excited, however, as the scientists caution that the tube may still be filled with rubble from the collapses at either end, or pooled lava which would have cooled while still in the tube, or even that the alignment is coincidental and that there is no tube at all!

Still, images like this are very exciting because, along with other recent discoveries, they make the viability of a permanent outpost on the Moon seem better and better.