Lunar rocks and soil, sampled by astronauts and numerous probes, provide evidence not only of the composition of the moon itself, but also of its history and connections to other cosmic bodies. Moon soil and rocks contain traces of chemical compounds such as methane and ammonia, as well as carbon dioxide and carbon monoxide. Traces of water ice have also been found on the moon, along with light metals such as silver, mercury and sodium.
In 2009, NASA launched the LCROSS mission, aimed specifically at searching for traces of water on the moon by crashing a satellite into the surface and observing the material thrown up by the impact. The plume of lunar soil that came from the satellite's crash landing in the Cabeus crater revealed not only hydrogen but also other chemicals, such as sodium.
The sources of sodium found in the lunar soil may be traceable to collisions with sodium-bearing meteorites. The presence of sodium, as detected by LCROSS and other probes, is consistent with conditions on comets and meteors. The solar wind, a stream of energy the sun emits, carries traces of sodium into the moon's thin atmosphere.
The presence of water and numerous other elements found on Earth and other bodies of the solar system reveal the moon's complex chemical profile and the presence of a water cycle and active atmosphere. The discovery of essential chemicals and compounds needed to sustain human life, such as hydrogen and sodium, hold promise for future exploration and colonization of the moon, and the exploitation of its resources for use on Earth.