ALSEP—Apollo Lunar Surface Experiments Package

anorthosite—a type of rock made up mainly of plagioclase feldspar, which has been found in all the Apollo lunar samples and constitutes most of the light-colored crust on the Moon

Archaea—a recently recognized domain of prokaryotic life. Single-celled microorganisms that lack a nucleus, are morphologically similar to bacteria but not closely related, having features such as genetic transcription and translation that are different. They are found in very high temperature environments, and include methanogens and hyperthermophiles that may be similar to the first life on Earth

ASTP—Apollo-Soyuz Test Project, a joint U.S.–U.S.S.R. mission

ATP—Advanced Technology Program of the National Aeronautics and Space Administration (NASA)

bacteria—single-celled micro-organisms lacking a nucleus, morphologically similar to Archaea, but not closely related

breccia—a rock composed of angular fragments of rocks and minerals in a matrix

CAPTEM—Curation and Analysis Planning Team for Extraterrestrial Materials

Chang’e—a Chinese National Space Administration lunar orbiter

Chesapeake—an ancient subsurface impact crater located in the Chesapeake Bay

CHEX—National Research Council’s Committee on Human Exploration

Chicxulub—an ancient subsurface impact crater located near Chicxulub, Mexico

chondrite—a type of stony meteorite containing chondrules, roughly spherical bodies containing pyroxene or olivine embedded in the matrix

chronostratigraphy—the branch of stratigraphy that studies the absolute age of rocks

cool early Earth—hypothesis that the surface of Earth cooled relatively quickly after the formation of the core and the Moon, such that oceans and conditions hospitable for life could exist by 4.3 Ga

Copernican—the lunar geologic period from about 1.1 Ga ago to the present

Cretaceous/Tertiary boundary—on Earth, the boundary between rocks of the Cretaceous and Tertiary periods, about 65.5 million years ago, around the time of a major extinction event

cumulates—igneous rocks formed by the accumulation of crystals from a magma

detrital zircons—zircon crystals found in erosional deposits. Some grains are as old as 4.4 Ga and are the oldest known samples of Earth

differentiated planetary body—a planetary body whose interior is formed of separate internal geologic units with distinct mineralogical characteristics, e.g., core, mantle, crust

Erastosthenian—the lunar geologic period from 1.1 Ga to 3.2 Ga ago

ESMD—NASA’s Exploration Systems Mission Directorate

EVA—extravehicular activity

Exosphere—the highest layer of an atmosphere

feldspathic—pertaining to rocks rich in feldspar minerals

Ga—one billion years

geochronology—determination of the time at which a rock crystallized, usually by radioactive decay of parent-daughter isotope pairs: U-Pb, Sm-Nd, K-Ar, or Rb-Sr

hyperthermophile—microorganisms that live in hot environments, above 60°C

igneous rocks—rocks crystallized from a magma

ISRU—in situ resource utilization

Isua greenstone rocks—a geological formation in southwestern Greenland (Isua) composed of ancient surface rocks

KREEP—lunar basalts and breccias that are rich in potassium (K), rare-earth elements (REE), and phosphorus (P)

Kuiper Belt—a region of the solar system distributed in a roughly circular disk extending from 40 to 100 astronomical units from the Sun

Late Heavy Bombardment (LHB) hypothesis—the theory that meteorite bombardment of the inner solar system declined after accretion of the planets and then peaked again at 3.9 Ga. This event is proposed to have limited the emergence of life on Earth

LCROSS—the Lunar Crater Observation and Sensing Satellite, a secondary payload to be launched with the Lunar Reconnaissance Orbiter

LEAG—the NASA Lunar Exploration Analysis Group (LEAG) is responsible for analyzing scientific, technical, commercial, and operational issues associated with lunar exploration

LPRP—the Lunar Precursor and Robotic Program of the Exploration Systems Mission Directorate

LRO—NASA’s Lunar Reconnaissance Orbiter

LSAM—NASA’s Lunar Surface Access Module

Lunar A—a Japanese Aerospace Exploration Agency lunar mission

lunar dynamo—for the ancient Moon, the possibility that a lunar magnetic field might have been generated by the internal motion of an iron-rich molten core

Lunar Magma Ocean hypothesis—the hypothesis that when the Moon formed, it was molten to a depth of hundreds of kilometers; its crystallization produced the primary crust and mantle

mafic materials—a dark-colored, igneous rocks rich in ferromagnesian minerals

magma—molten rock from the interior of a planetary body

mantle—the geologic zone above the core and below the crust

MER—NASA’s Mars Exploration Rover

obliquity—the angle between the orbital plane of an object and the plane of its rotational equator

olivine—a magnesium iron silicate mineral (FeMg)₂SiO₄

parautochthonous—a rock type intermediate in tectonic character between those found at the site of their formation and those that come from another site

Permian/Triassic boundary—on Earth, the layer of rocks between the Permian and Triassic periods, about 251 million years ago, the time of a major extinction event

petrology—a branch of geology dealing with the composition, mineralogy, origin, occurrence, history, and structure of rocks

plagioclase—a type of feldspar and one of the most common rock-forming minerals, (CaNa)(AlSi)₄O₈

pluton—a large body of igneous rock created by the subsurface intrusion of magma

pre-Nectarian period—the lunar geologic period from the formation of the Moon to about 3.9 Ga ago

protolith—the original rocks from which igneous, metamorphic, or sedimentary rocks were formed

pyroclastic—a type of rock material formed by volcanic explosion

pyroxene—a group of common ferromagnesian rock-forming minerals

regolith—on the Moon, the surface rock debris that overlies bedrock

remanent magnetization—also called paleomagnetism, the component of a rock’s magnetism that has a fixed direction and is independent of Earth’s magnetic field

rheology—the study of the deformation and flow of matter

SBE—surface boundary exosphere

SELENE—Selenological and Engineering Explorer, a Japanese Aerospace Exploration Agency lunar orbiter

SIM—the Apollo Scientific Instrument Module, which contained panoramic and mapping cameras, a gamma-ray spectrometer, a laser altimeter, and a mass spectrometer

SIMS—secondary-ion mass spectrometry

SMART-1—Small Missions for Advanced Research in Technology, a European Space Agency lunar mission

SMD—NASA’s Science Mission Directorate

SPA—the lunar South Pole-Aitken Basin

stratigraphy—the study of rock layers

TEM—transmission electron microscopy

U-Pb geochronology—the determination of the age of a rock based on radioactive decay of isotopes of U and Th to Pb, usually in the mineral zircon

VSE—NASA’s Vision for Space Exploration

xenolith—a foreign inclusion in an igneous rock

zircon—a silicate mineral (ZrSiO₄)