For centuries, man has dreamed of visiting the Moon. This finally happened on 20 July 1969, when Neil Armstrong and Buzz Aldrin of the United States set foot on the Moon in the southern Sea of Tranquility, just north of the Moon's equator. Since then, futurists and space enthusiasts have been anticipating the colonization of the Moon by humans, or at least further trips. This has failed to materialize, as the last manned landing on the Moon was in 1972. Things began looking up on 14 January 2004, when US President George W. Bush announced the Vision for Space Exploration, which made plans for another series of manned visits to the Moon beginning by 2020.
Even though it looks like man is going back to the Moon, the future of lunar exploration still looks spotty. Lunar exploration is extremely expensive. This is for two reasons: high launch costs -- due to rocket-based space launch technology, which is very inefficient, not to mention dangerous -- and a lack of economies of scale. The Vision for Space Exploration itself is likely to cost more than $20 billion USD (US Dollars), resulting in half a dozen Moon landings, but intense criticism has already been directed at the Vision, including from within NASA. Robotic probes are seen as having similar science returns for much lower cost. Manned lunar exploration is seen as prohibitively expensive, more appropriate during the 60s than today, as during the 60s the United States was concerned with showing its technological superiority to Soviet Russia.
For lunar exploration to really begin, humanity needs to develop a cheaper way of launching payloads into space. Current costs are approximately $10,000 USD - $25,000 USD per kilogram ($6,000 USD - $15,000 USD per pound) to low Earth orbit, and almost twice as much for launches to the Moon. This means that launching a 20.5 metric ton (45,000 lb) spacecraft like the Orion Crew Vehicle (with a six-person capacity) costs more than $200 million USD for launch costs alone. This clearly makes lunar exploration something that can currently only be attempted by the wealthiest nations or coalitions of nations.
The possibility of cheaper lunar exploration was given a boost by the 13 September 2007 announcement of the Google Lunar X Prize, a $5 million USD prize for the first team that can launch a rover to the Moon, have to rove 500 meters or more, and transmit back high-definition video from the surface of the Moon. There are also bonus prizes for such milestones as making a rover that can survive the lunar night, roving more than 5 kilometers (3.1 miles), capture images of man made objects on the moon, or detect ice in lunar craters. Many commentators on lunar exploration consider this kind of achievement to be the immediate future of lunar exploration, until alternative methods of space launch are developed to lower the cost of manned missions.