A potential gas source found on the moon's surface could hold the key to meeting future energy demands as the earth's fossil fuels dry up in the coming decades, scientists say. Mineral samples from the moon contain abundant quantities of helium 3, a variant of the gas used in lasers and refrigerators. "When compared to the earth the moon has a tremendous amount of helium 3," Lawrence Taylor, a director of the US Planetary Geosciences Institute, said. "When helium 3 combines with deuterium (an isotope of hydrogen) the fusion reaction proceeds at a very high temperature and it can produce awesome amounts of energy."Just 25 tonnes of helium, which can be transported on a space shuttle, is enough to provide electricity for the US for one full year."Helium 3 is deposited on the lunar surface by solar winds and would have to be extracted from moon soil and rocks. To extract helium 3 gas the rocks have to be heated above 800 degrees Celsius.Dr Taylor says 200 million tonnes of lunar soil would produce one tonne of helium.Only 10 kilograms of helium are available on earth. Indian President APJ Abdul Kalam has told the International Conference on Exploration and Utilisation of the Moon that the barren planet held about 1 million tonnes of helium 3. "The moon contains 10 times more energy in the form of helium 3 than all the fossil fuels on the earth," Mr Kalam said. However, Dr Taylor says that the reactor technology for converting helium 3 to energy is still in its infancy and could take years to develop. "The problem is that there is not yet an efficient type of reactor to process helium 3," he said.