text:  Countries are racing to establish a permanent human presence on the Moon, but they will need to protect astronauts from radiation and extreme temperatures. At least 100 metres deep and with overhanging walls, this Moon cave could be the perfect shelter. Scientists long suspected that the Moon had this underground, undiscovered world. Now they have proof. A team of researchers at the University of Trento in Italy used radar to identify this cavern in the lunar surface.