Shale gas is extracted by tapping gas from shale rock using a process called hydraulic fracturing, or fracking.

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Those resources consist of a lot of rock, a lot of sunlight that could be used to generate electricity to process the rock and, at least in the dreams of many lunar scientists, some 20 billion tonnes of frozen water believed to lie at the bottoms of craters near the poles, where it is sheltered from the evaporative effects of sunlight.

ECONOMIST: Spaceflight

It said markets had been hit by a combination of factors including the 2011 Japanese tsunami and the USA's interest in shale gas, which is extracted from shale rock using the controversial process of fracking.

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