KREEP
KREEP is lunar material rich in potassium, rare earth elements and phosphorus, left over from the Moon's magma ocean.
KREEP is an acronym for potassium (chemical symbol K), Rare Earth Elements and Phosphorus. It names a distinctive chemical component of lunar rocks that is also rich in uranium and thorium.
KREEP is thought to represent the last liquid of the lunar magma ocean. As the ocean crystallised, these elements did not fit into the main minerals and so gathered in the final dregs, between the crust and mantle. Later impacts and volcanism brought KREEP-rich material to the surface. Orbital measurements show it is concentrated in a region on the near side called the Procellarum KREEP Terrane, around Oceanus Procellarum and the Imbrium basin.
Because KREEP contains heat-producing radioactive elements, it may explain why volcanism lasted longer on the near side. Some lunar meteorites, such as those from the Sayh al Uhaymir 169 find, are rich in KREEP, while many others are poor, suggesting they come from regions far from the Procellarum area.
Related terms
Level: Expert Advanced