Water on the moon: how Earth's only natural satellite formed From The UK Telegrahp; 15 Jun 2010; By Andrew Hough Original Article The moon was probably formed after a massive space collision with a planet-sized object billions of years ago, in what Nasa described as the “big whack”.

Scientists believe the moon formed billions of years ago after a huge space collision. Photo: AFP/GETTY IMAGES Astronomers believe the object, most likely the size of Mars, collided with the earth about 4.6 billion years ago. As a result of the high-energy impact, a cloud of “vaporized” rock “shot off” the Earth's surface, before going into orbit around the planet. Scientists believe that cloud of rock then cooled and condensed into a ring of small, solid bodies. The bodies then gathered together to form our planet's only natural satellite, which we can see most nights. According to Nasa, the rapid collision released a large amount of energy and heat and as the moon melted, it created an "ocean" of magma (molten rock). Magma contained water, which eventually erupted via "fire fountains" on to the lunar surface.

As it cooled “dense, iron-rich materials”, then sank deep into the moon. As they solidified it formed a layer of rock beneath the “crust”. “As the crust formed, asteroids bombarded it heavily, shattering and churning it,” Nasa said. “The largest impacts may have stripped off the entire crust. Some collisions were so powerful that they almost split the moon into pieces. “One such collision created the South Pole-Aitken Basin, one of the largest known impact craters in the solar system.” Dr Francis McCubbin, from the Carnegie Institution for Science in Washington DC, who led the latest study into the moon’s surface, said most of the water evaporated during the volcanic activity. What was left, scientists have just discovered, was about 2.5 times the volume of the Great Lakes, in North America. They concluded that there was far more water on the moon than was previously thought and it is likely widespread deep under its surface. "I like to use the analogy of someone who's trying to make non-alcoholic beer. There's always going to be some alcohol left," Dr McCubbin later told the BBC. "Or another way of looking at it - if you took all of the water that was locked up inside the rocks of the Moon and put them on the surface, it would make a metre-thick layer covering the Moon." Nasa said that small eruptions are likely to have continued until as recently as 1 billion years ago. “Since that time, only an occasional impact by an asteroid or comet has modified the surface,” it said. “Because the moon has no atmosphere to burn up meteoroids, the bombardment continues to this day. However, it has become much less intense.”