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 – discus