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When astronauts return to the Moon, they should keep their eyes peeled for extraterrestrial artefacts – pieces of technology from alien civilisations that have wound up on the lunar surface either by chance or design. So says Ian Crawford, a researcher from University of London’s Birkbeck College in the UK. He told a SETI specialist meeting of the Royal Astronomical Society (RAS) in London last week that although he considers such a find a long-shot, it is definitely worth bearing in mind.