NASA's Lunar Reconnaissance Orbiter (LRO) detected water-ice, hydrogen, mercury, carbon monoxide, calcium and magnesium when the Lunar Crater Remote Observation and Sensing Satellite (LCROSS) impacted the Moon's Cabeus Crater near the lunar south pole.
The Centaur/LCROSS used rocket stage impacted at over 5,600mph (9,000kph), creating a debris plume 12 miles (19.3km) high. LRO monitored the ejected debris plume as it passed over the impact site that is permanently shaded from direct sunshine. With temperatures around 35 to 100 Kelvin (-238.15°C, -396.67F), volatile materials condense in the crater and stay there for billions of years, frozen and covered by micrometeorite impacts and Moon dust.
This region of the Moon also has permanently sun-illuminated mountainsides that are perfect for solar power generation and for locating a future Moon base. Finding water-ice reduces the need to transport it from Earth, greatly simplifying the mission and lowering the cost, though the mercury detected could be a problem as it is a major contaminant.
According to a Science Journal article Diviner Lunar Radiometer Observations of the LCROSS Impact, the LCROSS impact heated 323-2,150 sq.ft (30-200sq.m) of the Moon surface to at least 950 Kelvin (677°C, 1,250F), releasing around 661lbs (300kgs) of water ice during 4 minutes of LCROSS observations.
Some estimates state that up to 1 billion gallons of water (3.8 billion liters) of water could be trapped within the Cabeus Crater alone, making the Moon a lot less dry than previously believed.