Anorthosite: A granular, textured igneous rock regarded as having solidified at considerable depth. It is composed almost entirely of a soda-lime feldspar.

Apocynthion: The point in the orbit of a moon satellite which is farthest from the moon.

Apolune: See apocynthion.

Bow shock: The shock wave produced by the interaction of the solar wind with the earth's dipole magnetic field. It is also the outer boundary of the magnetosheath (transition region).

Breccia: A course-grained rock composed of angular fragments of pre-existing rocks in a fine-grained matrix.

Caldera: A broad crater-like basin surrounding a volcanic vent and having a diameter many times that of the vent.

Circadian rhythm: Relating to biological variations with a cycle of about 24 hours.

Cislunar: Pertaining to the space between the earth and moon.

Clast: A fragment of rock or mineral, commonly included in a larger rock.

Comprehensive sample: A 1-kilogram collection of rocks representative of a given area. Desired sample diameters range from approximately 3/8 inch to 1 1/2 inches.

Contingency sample: Approximately 2 kilograms of lunar material collected in the immediate vicinity of the lunar module during the early part of the first extravehicular period. This is done to increase the probability of returning a lunar sample to earth if early termination of extravehicular operations is necessary.

Densitometric: Relating to determining the degree of opacity of any translucent medium.

Diamagnetic cavity: An area having a magnetic permeability less than one.

Diurnal: Recurring daily. On earth, diurnal processes repeat themselves every 24 hours; on the moon, every 28 days.

Documented sample: A sample that is photographed before being picked up, the area photographed after sample removal, and a reference photograph taken to identify the location.

Double core tube sample: A sample obtained using two drive core tubes connected end to end.

Earthshine: Illumination of the moon's surface by sunlight reflected from the earth's surface and atmosphere.

Ecliptic: The plane defined by the earth's orbit about the sun.

Ergometry test: A test performed to measure muscular fatigue under controlled conditions.

Front: The outer slopes of a mountain range that rises above a plain or plateau.

Geomagnetic tail: An elongation of the earth's magnetic field whereby it is drawn in the anti-solar direction to an undetermined distance. It is also called the nagnetotail.

Gnomon: A rod mounted on a tripod in such a way that it is free to swing in any direction and indicate the local vertical.

Hummocky: Multiple low, rounded hills or knolls.

J-missions: A classification of Apollo lunar exploration missions for which provisions are made for extended lunar surface stay time, surface vehicular mobility and communications, and more extensive science data acquisition.

Kilocalorie: An amount of food having an energy-producing value of one large calorie (equivalent to 1000 gram calories).

Limb: The outer edge of the apparent disc of a celestial body, as the moon or earth, or a portion of the edge.

Lunar libration: A point in space which, from the viewpoint of an observer on earth, is about 60 degrees from the earth-moon axis in the direction of the moon's travel and on its orbital path.

Lunation: The average period of revolution of the moon about the earth with respect to the sun. A period of 29 days 12 hours 44 minutes 2.8 seconds. Also called a synodical month.

Magnetosheath: The region between the solar wind bow shock and the earth's dipole magnetic field. It varies in size and, within the region, the solar wind is reduced and the magnetic field is poorly defined. It is also called the transition region.

Magnetosphere: The region of the earth's atmosphere where ionized gases contribute to the dynamics of the atmosphere and where the forces of the earth's magnetic field are predominant.

Magnetospheric plasma: Plasma evolved in the magnetosphere.

Magnetotail: See geomagnetic tail.

Magnetopause: The boundary between the magnetosheath (transition region) and the earth's dipole magnetic field.

Mare: A large, dark, flat area on the lunar surface (lunar sea).

Mascons: Large mass concentrations beneath the lunar surface. They are believed to be large bodies that have impacted the lunar surface.

Meru: Milli earth rate unit. One thousandth of the earth's rotational rate.

Metric photography: Photography having an appropriate network of coordinates or reference points to permit accurate measurements.

Monoscopic photograph: A single photograph of a given area, or subject obtained with a camera having one lens system and shutter.

Morphological: Relating to the shapes and contours of objects or areas.

Moulton Point: A theoretical point on the sun-earth axis thought to be located about 940 000 statute miles from the earth in the anti-solar direction. It is also designated as the Ll libration point of the earth.

Noble gases: Monatomic gases that are relatively inert.

Olivine: An igneous mineral that consists of a silicate of magnesium and iron.

Pericynthion: The point in the orbit of a moon satellite that is nearest to the moon, or the point in the trajectory of a vehicle that is nearest to the moon.

Perilune: See pericynthion.

Phenocrysts: Crystals in igneous rocks that are larger than the crystalline matrix in which they are imbedded.

Planar: Two-dimensional.

Plasma: An electrically conductive gas comurised of neutral particles, ionized particles, and free electrons, but which as a whole, is electrically neutral.

Plasma sheet: As used in this report, the term refers to a region in the center of the geomagnetic tail, approximately 10 earth radii in width, in which there is a marked increase in particle flux.

Porphyritic: The texture of rocks which contain distinct crystals imbedded in a relatively fine-grained groundmass.

Pyroclastic rocks: Rocks formed by fragmentation as a result of volcanic action.

Pyroxene: A mineral occurring in short, thick, prismatic crystals, or in crystals of square cross section; often laminated, and varying in color from white to dark green or black (rarely blue).

Radial sample: A sample consisting of material taken from a crater's ejecta field at a crater's rim, at a distance equal to the crater's radius, and at a distance equal to the crater's diameter.

Radon: A radioactive gaseous element with atomic number 86 and atomic masses of 220 and 222. Formed by the radioactive decay of radium.

Regolith: The surface layer of unsorted fragmented material on the earth or moon that overlies solid material

Rille: A long, narrow valley on the moon's surface.

Scoriaceous: Having the characteristics of rough, vesicular, cindery, usually dark lava.

Selenodetic: Relating to the branch of applied mathematics that determines by observation and measurement the positions of points on the moon's surface and the size and shape of the moon.

Selenological: Relating to the branch of astronomy that deals with the moon.

Slikensides: Smooth, grooved and polished surfaces of rocks produced by friction on fault planes and joint faces.

Solar corona: The outer visible envelope of the sun.

Solar wind: Streams of particles (plasma) emanating from and flowing approximately radially outward from the sun.

Spectrometric: Relating to the measurement of wavelengths of rays of a spectrum.

Stereoscopic photographs: Two photographs obtained of a given area or subject from different angles so that the images, when viewed through a stereoscope, appear as a three-dimensional reproduction of the area or subject photographed.

Talus: An accumulated mass of angular rock debris on a hill side or at the foot of a mountain.

Terminator: The border between the illuminated and dark portions of the moon or planets

Transition region: See magnetosheath.

Umbra: The darkest portion of the shadow of a large body such as the earth or moon wherein light is completely blocked.

Vesicular: Containing small spherical cavities.

Zodiac: An imaginary belt that extends 8 degrees on either side of the ecliptic. It includes the paths of the moon and principal planets.

Zodiacal light: A faint glow seen along the zodiac in the west after sunset and in the east before sunrise.