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It is the nearest and most dominant object in our night sky, and has inspired artists, astronauts and astronomers. But fundamental questions remain about our only natural satellite. Where does the Moon come from?

Although humans first walked on the Moon over four decades ago, we still know surprisingly little about the lunar body's origin. Samples returned by the Apollo missions have somewhat confounded scientists' ideas about how the Moon was formed. Its presence is thought to be due to another planet colliding with the early Earth, causing an extraordinary giant impact, and in the process, forming the Moon. But, analysing chemicals in Apollo's rock samples has revealed that the Moon could be much more similar to Earth itself than any potential impactor. Geochemist Professor Alex Halliday of the University of Oxford, and Dr Jeff Andrews-Hanna, Colorado School of Mines – who is analysing the results from Nasa's Gravity Recovery and Interior Laboratory (GRAIL) lunar mission – discuss the theories and evidence to-date.

Are we Going Back?
Settling the question of the Moon's origin seems likely to require more data – which, in turn, requires more missions. ´óÏó´«Ã½ Science correspondent Jonathan Amos tells us about the rationale and future prospects for a return to the Moon, including the Google Lunar XPrize.

As the Moon's commercial prospects are considered, who controls conservation of our only natural satellite? If commerce is driving a return to the Moon, who owns any resources that may be found in the lunar regolith? Dr Saskia Vermeylen of the Environment Centre at Lancaster University is researching the legality of claiming this extra-terrestrial frontier.

(Photo: Presenter Lucie Green. ´óÏó´«Ã½ copyright)