If, like me, you have a passion for the mysterious and unknown, I suggest you gaze up at the sky tonight and direct your attention towards the Moon, for this eerier glowing satellite is one of the greatest mysteries known to humankind.
Exactly how the Moon was formed has yet to be adequately explained by science, due in part to a lack of knowledge concerning the structure and origin of its mantle. However, thanks to data recently obtained by the Japanese probe Kaguya, which was placed in orbit around the Moon from November 2007 to June 2009, scientists think they’ve found an important piece of the puzzle.
The Giant Impact theory, the most widely accepted theory of how the Moon came to be, suggests that it was formed about 4.5 billion years ago when a Mars-sized body collided with Earth. So huge was this collision that a massive amount of debris was thrown off into space, which coalesced into a ball to form the Moon.
With the use of sensors onboard the Kaguya probe, the Japanese team of astronomers found, in concentric rings around a number of the Moon’s major craters, exposures of rock rich in the mineral olivine. The study, headed by Dr Satoru Yamamoto of Japan’s National Institute of Environmental Studies in Tsukuba, appeared online in the journal Nature Geoscience on July 5, 2010. Dr Yamamoto told BBC news: “These craters with olivine-rich sites are very large, with diameters of several 100km to a 1,000km.”
Olivine, which is a relatively heavy mineral, is one of the main components of the Earth’s mantle. That it’s also been found in the rims of lunar craters – areas where the crust of the Moon has been broken – has confirmed scientists’ expectations, adding a further chapter to how the Moon is believed to have been formed. The evidence suggests that, during the formation of the Moon, after its crust had cooled and hardened, the molten liquid beneath underwent a process of ‘overturning’, bringing olivine-rich mantle from deep within the lunar bowels to within the base of the crust.
Although, in Yamamoto’s expert opinion, the olivine they found is from the mantle of the Moon, having been rendered exposed by the impact of asteroids and comets, “we can’t rule out the possibility of a crustal origin.” Only by studying samples of lunar olivine will it be possible to answer this question with certainty. But, first of all, the material will need to be retrieved during a future Moon mission.