increasing at 3.8 cm/year
'' Continents approached
- * *" present distributions
Ocean begirt on Earth.
Billion (10s) years ago
Over time, the movement of continents, oceans and winds slows down the Earth's rotation. It also causes the Moon to spiral away from Earth by the principle of conservation of angular momentum. The curve at right hypothesizes the change of lunar distance in the past. It is hypothetic because the past distribution of land and sea is not ascertained. Today the Moon is receding from Earth at average rate of 3.8 cm/year, a result obtained by laser ranging since the Apollo missions.
1. Mare Crisium
2. Mare Nectaris
3. Mare Serenitatis
4. Mare Imbrium
5. Mare Humorum
6. Mare Humboldtianum
7. Oceanus Procellarum
8. Montes Apenninus
9. Mare Orientale
10. Mare Australe
11. Mare Moscoviense
15. South-Pole Aitken (basin, dia. 2300 km)
Abundance of Elements The relative amount of each element in a given object such as a star, planet or satellite.
Accretion The increase of mass of a body by the accumulation of smaller objects that collide and stick to it.
Age of the Moon ^^ The period that has elapsed since the last new moon. It starts at "zero" day (exact new moon). Al bedo Fraction of sunlight reflected from a planetary surface. The albedo of lunar maria are 5-10 %; highlands are 12-18 %.
Angular Momentum ^fti A property of any rotating or revolving body. Its value depends on the distribution of the body's mass and velocity about the axis of rotation or revolution. The total angular momentum is constant in a closed system. Anorthosite MSS Light-colored rock from lunar highlands or beneath mare basalts, rich in silicon, calcium and aluminum. Apogee Stffii The farthest point on the Moon's orbit from the Earth.
Apollo Missions N^SS.PI'ii^ The American NASA (National Aeronautics and Space Administration) program to land humans on the Moon. The first manned landing is Apollo 11 (1969 July 20), and the last is Apollo 17 (1972 December 11). Apollo 13 (1970 April) aborted in the third day of the mission. A total of 12 Apollo astronauts landed on the Moon. Basalt ^^^ Dark-colored rock formed from solidified lava. See also Mare Basalt.
Breccia ^RS On the Moon, it refers to the rock of 2 or more types cemented together by heat or pressure (e.g. meteorite impacts). Caldera A type of volcanic crater formed primarily by a sinking of its floor rather than by the ejection of lava.
Catena Latin for chain of relatively small craters (plural: catenae).
Center of Mass The point in a system of bodies (e.g. Earth-Moon) which acts as if all the mass were concentrated there. Colongitude l^fe® A measure of the Sun's relative position. On the Moon, it is same as the selenographic longitude of the morning terminator, measured westwards from the prime meridian. Thus its value is 00 at first quarter, 900 at full moon, 1800 at last quarter & 2700 at new moon.
Crater A generic term for circular depression on surface, typically a ring mountain or a walled plain which has relatively large and flat floor. Craters are of either impact or volcanic origin. Crescent The phase of the Moon when it is less than half illuminated as seen from the Earth.
Crust The outermost solid layer of a planet or satellite.
Dark Mantle Deposit MtttSffiW Remarkably dark deposit on the Moon's surface. It contains a mixture of small black and orange glass debris, possibly formed from quickly cooled droplets during fountain-like volcanic eruption. Differentiation ^ftff^ The formation of variety of rock types and layers (crust, mantle etc.) from an initial single parental magma. Diurnal MIBfi^ Happening daily.
Dome / Sfi Low rounded elevation formed by volcanism, typically 5 to 20 km in diameter and slope under 50.
Dorsum (plural: dorsa) Latin for wrinkle ridge. Long narrow rising feature on the mare floor, resulted from surface shrinkage following the cease of volcanism, or buckling of the lunar crust due to the weight of accumulated lava in the impact site. Earthshine ttE / fti^E The faint illumination on the dark side of a crescent, caused by sunlight reflected from the Earth. Ejecta fli^W Material thrown out from an explosive event, such as a crater-forming impact or volcanic eruption. Ejecta Blanket fl^s^w The area immediately outside the rim of an impact crater where the ejecta has completely covered the underlying terrain.
Farside of the Moon The side of the Moon facing away from the Earth.
Fault A fracture of surface along which there has been slippage, either vertical or horizontal.
First Quarter ^^ The phase of the Moon that occurs midway between new and full moon, when half of the Moon is illuminated. At first quarter, the Moon has moved 1/4 of its orbit around the Earth and lies 90 east of the Sun. Full Moon ffi^ / ^ The phase of the Moon when it is fully illuminated and 1800 away from the Sun, as seen from the Earth. Ghost Crater The bare hint of a crater formation that has been destroyed or heavily modified by some later action.
Giant Impact Theory A popular theory (hypothesis) for the origin of the Moon from impact debris when a Mars-sized proto-planet collided with the proto-Earth in about 4.5 billion years ago, developed after the Apollo missions. Graben tt® Sunken area between faults.
Harvest Moon f^^l The full moon closest to the autumnal equinox when it rises at minimum delay time in successive days.
Highlands ^tt Raised areas on the Moon, light-colored, heavily cratered and chemically distinct from the maria.
IAU International Astronomical Union, an assembly to govern the world of astronomy, founded in 1919.
Igneous ^^^ Referring to processes that involve the formation and solidification of hot, molten magma or lava.
Illumination EE® A measure of moon phase, equal to the ratio of illuminated area to the total area of the Moon disc. New moon gives illumination = 0 %, full moon gives 100 %. Impact Basin IS^^ift A vast depressed surface (size larger than about 300 km) caused by colossal impactors. Quite often it is encircled by multiple mountain rings. A typical example is the farside basin that holds Mare Orientale. Isotopes Iff; Atoms of the same element having same number of protons but different numbers of neutrons in their nuclei. KREEP ^S^S A special type of rock concentrated in Oceanus Procellarum and Mare Imbrium. It is relatively rich in potassium
(symbol K), rare-earth elements (REE), phosphorus (P) as well as other radioactive elements such as thorium and uranium. Lacus ® Latin for lake. A "small version" of lunar mare.
Laser Ranging Establishment of precise Earth-Moon distances by aiming and reflecting laser beams between them.
Last Quarter ^^ The phase of the Moon that occurs midway between full and new moon, when half of the Moon is illuminated. At last quarter, the Moon has moved 3/4 of its orbit around the Earth and lies 900 west of the Sun. Late Heavy Bombardment The event that postulates the Moon was heavily bombarded around 3.9 billion years ago.
Lava Molten rock that reaches the surface during a volcanic eruption. See also Magma.
Libration ^^ffil The apparent vertical or horizontal rocking motions of the Moon as it orbits around the Earth. The amount of libration is measured by the shift of longitude and latitude at the center of the Moon disc. LTP Abbreviation for "Lunar Transient Phenomena" or "Transient Lunar Phenomena". A controversial observed phenomena of weird happenings or changes on the Moon's surface. It only lasts for a short while.
Lunation (Synodic Month) ^^^ The period of time taken for the Moon to go through a complete cycle of phases. Magma ^^ Subsurface molten rock. When it reaches the surface during a volcanic eruption, it is called lava
Mantle ft / ft'[§ The thicker layer in the interior of a planet or satellite, underneath the crust but overlying the core, and differing in composition from both.
Mare ^ / ^^ Latin for sea (plural: maria). The broad dark plain formed from ancient lava outflow from the Moon's interior. Mare Basalt ^^SSS Dark rock on lunar maria, enriched by heavy metals like iron and titanium. Few samples of mare basalt from the Apollo missions are vesicular; they suggest that trapped gases escaped from the rocks during mare formation. Mascon WmW / fi^S^M Abbreviated from the term "mass concentration". An area on the Moon composed of relatively denser material, as evidenced by an increased gravitational pull on orbiting spacecraft. Meteoroid Small low-mass interplanetary debris. A meteoroid that hits the Earth's or lunar surface is called Meteorite PMS
Mineral Inorganic solid with a definite composition and crystal structure formed through geologic processes. Chemically it is a bonding of silicates (silicon + oxygen) with composites of calcium, aluminum and/or magnesium etc. Minerals are classified according to their chemical compositions. They are the basic components of rock. Moment of Inertia H'^ffi A measure of a body's ability to resist changes in its angular velocity about a given axis. The Moon's moment of inertia is slightly less than that of a homogeneous sphere, so the Moon might have a small dense core. Mons | Latin for mountain. A group of isolated mountains or mountain ranges are Latinized as Montes
Moonquake ^^ Sudden trembling of the Moon caused by the abrupt release of internal energy, meteorite impacts or landslides. Nearside of the Moon ^H® The side of the Moon facing the Earth.
New Moon ^^ / ^ The phase of the Moon when it is directly between the Earth and the Sun.
Occultation ^ The movement of one celestial object (e.g. a star) behind another (e.g. the Moon).
Oceanus ^ Latin for ocean. The "large version" of lunar mare. Oceanus Procellarum is the only feature so named.
Palus S Latin for marsh or swamp. A "small version" of lunar mare.
Penumbra The less dark outer region of the shadow of the Earth.
Perigee The nearest point on the Moon's orbit from the Earth.
Phase Illuminated portion of the Moon disc. There are four specific phases: new moon, first quarter, full moon and last quarter.
Promontorium W / Mffi Latin for promontory or cape.
Radiometric Dating Age-determination of rocks by comparing the decay of radioactive elements such as the isotopes of potassium ( K), rubidium ( Rb) and uranium ( U) embedded in the samples. Rays, Lunar Streaks (normally bright) radiating from certain impact craters of the Moon.
Regolith i^i / From the Greek for "blanket of stone". A layer of loose and broken rock and dust on the crust of a planet or satellite. The lunar regolith ^^ contains a small amount of tiny, black glass beads produced by micrometeoroid impacts. Remote Sensing ^^ Gathering of information without actual physical contact with what is being observed.
Rima ^ / ^hM / S/ Latin for rille (plural: rimae). A narrow and relatively long cleft, slumped channel or valley on the surface of the Moon, caused by ancient running lava or slight pulling of ground to either side. Ritcher Scale ^^f^ffeK^® A scale to determine the magnitude of earthquake (and moonquake). Each whole number increase in scale magnitude represents 31.6 times more energy release than the preceding magnitude. Thus magnitude 8.0 releases 1000 times more energy than magnitude 6.0. Magnitudes below about 2.0 are generally not noticed by human. Roche Limit i^-^fSPfi The minimum distance from a planet's center at which a satellite will not be disrupted by the planet's tidal force. Its theoretical value is 2.46 times the radius of the planet (16,000 km from the center of Earth). Rock ^ A solid mass on the crust of a planet or satellite, largely composed of silicates (composites of silicon and oxygen) while the rest may be one or more types of other minerals. Rupes MS / / MM Latin for scarp, cliff or fault.
Saros iSM® A cycle of nearly identical lunar or solar eclipses that recur every 223 lunations (6585.32 days or 18.03 years). Secondary Craters / Impact craters produced by the ejecta of a large impact-crater.
Seeing A measure of the steadiness of air through which a celestial object is observed.
Seismometry ffeK?!® Measurement of seismic waves, such as those produced by earthquakes or moonquakes. Selenographic Belonging or relating to the surface of the Moon. "Selene" is the Greek goddess of the Moon.
Shield Volcano Mff^^l Volcano that appears in gently sloping cone, constructed of solidified lava flows.
Shock Wave S® An abrupt ripple of compression across a medium, due to a fast object hitting on or moving through the medium. Sinus ^ Latin for bay. A "small version" of lunar mare, usually in the appearance of a bay but can be irregular in shape. Tectonics tfe^W^ffffl Large-scale movements of the crust of a planet or satellite, such as land rising to form a mountain. Terminator The boundary on the Moon between day and night, or between light and shadow. At the morning terminator, the Sun is rising over that part of the Moon; at the evening terminator, the Sun is setting. Terraced Wall n't® The inner wall (of a lunar crater) that appears in terrace structure. Terrain it® / tfe^ A generic term referring to any surface area with a distinctive geological character.
Tidal Force 5 ffl^ / The ability of a celestial body A to raise tides on another body B. It is quantified by the difference of gravitational forces experienced by B between its surface and center, and is inversely proportional to the cube of the distance between the two bodies. The lunar tidal force acting on Earth is 2.2 times greater than the Sun's tidal force. Umbra The darker core of the shadow of the Earth, typically cone shaped, and surrounded by a lighter penumbra shadow. Within the umbra, the Moon is completely obscured from direct sunlight; a total lunar eclipse will be seen on Earth. UT ^^BB Abbreviation for "Universal Time". For time conversion, UT = Hong Kong Standard Time - 8 hours. Volatile ff^fifi Easy to vaporize. Volatile substances have low boiling points, e.g. water, hydrogen, nitrogen, methane, ammonia, CO2. Vallis ^ / ^^ / ff Latin for lunar valley that appears as a broad trough of volcanic origin or a chain of overlapping craters. Viscosity ft® Resistance to flow. The lunar lava is believed less viscous than the terrestrial and hence can flow in long distance. Volcanism Any process to transfer molten material and gases in the interior of a planet or satellite to its surface.
Wrinkle Ridge Sometimes called mare ridges because they are found usually in mare floors. See also Dorsum.
Atlas & Maps
1. Atlas of the Moon, Antonin Rukl, 1996, Kalmbach Books.
2. The Hatfield Photographic Lunar Atlas, Jeremy Cook, 1998, Springer.
3. Zdenek Kopal, A New Photographic Atlas of the Moon, 1971, Taplinger Publishing Company.
4. Lunar & Planetary Institute - Resources
Images from Ranger, Lunar Orbiter, Apollo, Consolidated Lunar Atlas http://www.lpi.usra.edu/resources/
5. Nomenclature and Topography Maps (Moon)l http://planetarynames.wr.usgs.gov/
6. Clementine Images http ://www.cmf.nrl.navy. mil/clementine/
7. Google Moon http://www.google.com/moon/
8. Patrick Moore on the Moon, Patrick Moore, 2001, Cassell & Co.
9. Observing the Moon, Gerald North, 2000 edition, Cambridge University Press.
10. Exploring the Moon through Binoculars and Small Telescopes, E. H. Cherrington, Jr., 1984, Dover Inc.
11. Pictorial Guide to the Moon, Dinsmore Alter, 3rd edition, Thomas Y. Crowell Company.
12. WinJupos http://www.grischa-hahn.homepage.t-online.de/astro/winjupos/ (Moon ephemerides)
13. Virtual Moon Atlas http ://www.astrosurf.com/avl/UK download.html
14. The Sky Astronomy Software, Software Bisque. (Moon orbital simulation)
Lunar Science & Geology
15. Geologic History of the Moon, Don Wilhelms http://cps.earth.northwestern.edu/GHM/
16. Geology of the Moon: A Stratigraphic View, Thomas A. Mutch, 1970, Princeton University Press.
17. The Modern Moon: A Personal View, Charles A. Wood, 2003, Sky Publishing Corporation.
18. The Once and Future Moon, P. D. Spudis, 1996, Smithsonian Institution Press.
19. The Moon (a concise paper by S. R. Taylor), Encyclopedia of the Solar System, second edition.
20. Introduction to Lunar Science (Chinese text), China Astronautic Publishing House, ISBN 7-80218-001-5
21. Planetary Science Research Discovery http://www.psrd.hawaii.edu/
22. USGS Planetary GIS Web Server http ://astro geology.usgs.gov/Projects/webgis/
23. Remote Sensing Tutorial http://rst.gsfc.nasa.gov/Front/tofc.html (Section 18 & 19)
24. The Moon Book, Kim Long, 1998, Johnson Books.
25. Astronomy For Entertainment, Y. Perelman, translated by A. Shkarovsky, 1958, Moscow. (Chapter 2)
26. Epic Moon, William P. Sheehan & Thomas A. Dobbins, 2001, Willmann-Bell, Inc.
27. The New Solar System, 4-th edition, Sky Publishing Corp. and Cambridge University Press. (Chapter 6, 10)
28. Lunar Notebook, Charles A. Wood, Sky & Telescope magazine, issues since May 2000.
29. The Planetary Scientist's Companion, K. Lodders & Bruce Fegley, Jr., 1998, Oxford University Press.
30. Mathematical Astronomy Morsels, Jean Meeus, 2000, Willmann-Bell, Inc. (Chapter 1 - 6)
31. Allen's Astrophysical Quantities, Arthur N. Cox, 4-th edition, AIP Press. (Chapter 12)
Other Web Resources
32. Apollo Over the Moon http://www.hq.nasa.gov/office/pao/History/SP-362/contents.htm
33. Lunar Science Results http://www.lpi.usra.edu/expmoon/science/science index.html
34. Giant Impact Hypothesis: Strengths & Weaknesses http://en.wikipedia.org/wiki/Giant impact hypothesis
35. Moondust http://science.nasa.gov/headlines/y2006/28dec truefake.htm
36. Charles Wood's Moon & LPOD http://www.lpod.org/
37. An Amateur's Moon, Alexander Vandenbohede http://users.pandora.be/lunarsite/
38. Lunar Transient Phenomena (LTP) http://www.ltpresearch.org/nav.htm
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