NASA is planning to crash a space probe on the surface of the moon in 2009 as part of larger mission to search for water.

The explosion, which will be seen from Earth with a telescope, will open a hole about five metres deep. The probe's mothership will then look for traces of ice or vapour in the plume of debris released from the collision.

The mission is similar to NASA's Deep Impact expedition last July, which blasted into a comet.

An artist's rendering of the probe approaching the moon prior to impact. (NASA/John Frassanito and Associates)

The moon collision and orbiter mission will be the first of several lunar robotic projects before NASA sends astronauts to the moon. That manned expedition is set for 2018.

The orbiter is scheduled to launch in October 2008 and will circle the moon for at least a year. It will map the surface, searching for water and potential future landing sites to send astronauts.

Scientists will also use robots to search other resources such as hydrogen and metals that human explorers could use.

The entire mission will cost more than $600 million US.