protoliththe original rocks from which igneous, metamorphic, or sedimentary rocks were formed

pyroclastica type of rock material formed by volcanic explosion

pyroxenea group of common ferromagnesian rock-forming minerals

regolithon the Moon, the surface rock debris that overlies bedrock

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

rheologythe study of the deformation and flow of matter

SBEsurface boundary exosphere

SELENESelenological and Engineering Explorer, a Japanese Aerospace Exploration Agency lunar orbiter

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

SIMSsecondary-ion mass spectrometry

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

SMDNASA’s Science Mission Directorate

SPAthe lunar South Pole-Aitken Basin

stratigraphythe study of rock layers

TEMtransmission electron microscopy

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

VSENASA’s Vision for Space Exploration

xenolitha foreign inclusion in an igneous rock

zircona silicate mineral (ZrSiO4)

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