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Lunar Prospector Glossary

Term	Definition
Apogee	In an elliptical orbit, the point at which the satellite is farthest from the surface of the body it is orbiting.
Apollo	U.S. manned space program culminating in 6 successful lunar landings
Astronaut	a person that goes into space or is trained for space flight
Basalt	a dark-colored rock that most commonly solidifies on the surface in the form of lava flows; dominant rock type in lunar maria
Basin	a large curcular area on the Moon, surrounded by one or more mountainous rings
Breccia	lunar rock fragments, or aggregates, fused together by heat and pressure
Centrifugal Force	force created by spinning objects which pulls the object moving in a curved path
Centripetal Force	force pulling toward the center that keeps an object moving in a curved path
Cislunar	the space between the Earth and the Moon
Crater	ring-like depression formed by the impact of meteorites and other space debris
Dehydrate	to remove water or moisture from an object
Density	a measure of how much mass is contained within a given volume, mass per unit volume
Descartes	landing site of Apollo 16 in Central Highlands
Diurnal	pertaining to lighted phase of the day
Effluent	any liquid or gas discharged from a spacecraft
Egress	to exit or leave, i.e. to leave the spacecraft
Ejecta	rock material ejected during the process of impact of by volcano
Elliptical	Earth's orbital plane, viewed from the sun or projected against the background of stars
Erosion	where rock materials are disintegrated or dissolved
Fault	a fracture along with rock masses have been displaced or moved
Fra Mauro	site of Apollo 14 landing in Easter Oceanus Processarum
Friable	Easily crumbled
Gamma Rays	highly penetrating rays emitted by radioactive substances
Gravity	the attraction between two objects because of their mass
Hadley-Apennine	landing site of Apollo 15
Highlands	brighter areas of the lunar surface (also called Terra)
Impact	a forceful collision, i.e. impact of the meteoroid on the Moon
Inertia	resistance to any sudden change in state, motion, or rest
Ingress	to enter
In Situ	in original position
Lava	molten rock (magma) that has reached the surface
Mantle	an intermediate layer of the Moon between the outer layer and the central core
Mass	a measure of the actual amount of matter or in a body
Mare (Maria)	cooled lava flows that are level and relatively smooth that appear as darker areas on the lunar surface
Mare Tranquillitatus	landing site of Apollo 11
Meteorite	a particle or rock traveling through space which impacts on the planet's or Moon's surface
Moon	an object that orbits a planet and reflects the light of a star
Oceannuys Porellarum	landing site of Apollo 12
Orbit	the path of a body, captured by gravity, around another body
Payload	cargo or passenger aboard an aircraft, rocket or missile
Perigee	in an elliptical orbit, the point at which the satellite is nearest the surface of the body it is orbiting
Phase of the Moon	Apparent shape change as seen from Earth
Projectile	body that strikes the lunar surface
Pyroclastic	volcanic material explosively ejected from a volcanic vent
Radiation	energy emitted from ma source such as a start
Ranger	NASA's unmanned lunar photographic probes designed to impact on the Moon
Ray	light-colored streak radiating out from craters
Regolith	blanket on lunar debris (also called lunar soil)
Rehydrate	to put water or moisture back into the body or tissue
Rille	valley-like features of two main types, straight and sinuous
Rim	elevated region around craters and rilles
Solar Wind	particles, mostly hydrogen and helium, emanating from the sun
Surveyor	NASA's lunar probes designed to soft land on the lunar surface
Taurus-Littrow	landing site of Apollo 17
Terminator	line separating the lighted and dark areas of the Moon
Trajectory	the path of a projectile or rocket in it's flight
Velocity	the speed of an object