The two unmanned spacecraft of NASA's $79 million Lunar Crater Observation and Sensing Satellite (LCOSS) mission will crash into the Moon in the early hours of Friday morning, 1231 BST, in an attempt to detect the presence of water-ice.

The two LCOSS components - the huge Centaur rocket upper stage and a smaller 'shepherding spacecraft' - which have been connected ever since their June launched from Cape Canaveral, Florida, separated Thursday night.

The 'shepherding spacecraft' will guide the 2.2-ton rocket to Moon's south pole crater Cabeus, which is a shaded 98m-wide depression.

The rocket will hit against the Moon's surface with two-times the speed of a bullet. The impact of the massive collision, equivalent to one-and-a-half tonnes of TNT, will expectedly throw 350 metric tonnes of debris to a nearly 10km altitude.

Four minutes after the rocket's plunge, the 'shepherding spacecraft' will descend through the debris plume, and slam into the Moon's surface generating a second, smaller debris cloud.

However, till it hits the lunar surface, the 'shepherding spacecraft' will use onboard spectrometers to continuously collect data in the sun-lit plume, searching signs of water, hydroxyl compounds
(OH), salts, clays, hydrated minerals and organic molecules.

About the target site, Anthony Colaprete, LCOSS mission's chief investigator, said that the decision to target the Cabeus crater was based on the most recent data received NASA's Lunar Reconnaissance Orbiter (LRO).