US space agency NASA has said it plans to start work on a permanently-occupied base on the Moon after astronauts begin flying back there in 2020. The base is likely to be built on one of the Moon’s poles and will serve as a science centre and possible stepping stone for manned missions to Mars. NASA is also expected to ask other countries – and businesses – to help it build the base. According to venerable news resource Reuters, funds for building the lunar base will be diverted from the space shuttle programme, which is to be phased out by 2010. After the Columbia space shuttle accident, US President George W Bush announced plans to send astronauts back to the moon by 2020.