aware of the threat of an orbital impact during space missions and monitors this junk constantly. The agency estimates that there might be more than 3,000 satellites orbiting Earth. In February 2008, for example, the United States blew up a satellite that contained toxic fuel. It was exploded over the Pacific Ocean so that it could not fall and harm humans. Some scientists speculate that one day there might be orbiting"garbage collector" machines to pick up the debris. Since the space surveillance mission began, almost 1Zooo objects that were tracked reentered Earth's atmosphere. Most objects that reenter the atmosphere either burn up or reenter over water. As a result, the risk of someone getting hit on the head by on these objects is very remote. Nearly three-quarters of the is covered by water, and large areas of planet Earth's land are uninhabited