Primer on Nearside Lunar Geology: A Table of 835 Lunar Features by Geologic Era with Wilhems' Charts and Table of Lunar-Earth Analogues Org. 12/1/2006 Rev. 12/26/2006

Go to: Summary Table of Geologic Eras | Feature Types with Moon-Earth analogues | List of Features with Geologic Eras by Name | List of Features with Geologic Eras by Lunar Latitude and Longitude | Impact Basin Structural Features | Detail Table of Geologic Eras with example features | Near-term lunar satellite mission websites

Summary and Introduction

An introduction to the geologic history of the nearside of the Moon and finder lists for 835 lunar craters and other features by lunar geologic era are provided based on Don Wilhems' 1987 classic, A Geologic History of the Moon, USGS Survey Paper 1348, Dr. Charles Wood's Lunar Picture of the Day (LPOD) image gallery, and USGS-NASA Geologic Atlas of the Moon charts, prepared by NASA as part of the Apollo program. Heavy reliance is made on 12 color geologic maps, Charts 1 through 12, at the back of Wilhems' Geologic History of the Moon in order to illustrate which portions of the nearside Moon relate to several major lunar geologic eras.

Examples of various lunar features are illustrated by linking to images at Wood's LPOD and NASA's Earth Observatory websites. This primer is intended to provide a quick index reference to images of key lunar features to support local amateur public and school star parties on the geologic era of features near the lunar terminator. It also should be considered a prefatory introduction to lunar geology prior to reading more in-depth books such as Wood's The Modern Moon: A Personal View, the introductory chapter to Westfall's Atlas of the Lunar Terminator, or Wilhems' technical Geologic History.

A freeware software alternative to this website is Christian Legrand's and Patrick Chevalley's Version 3.5, Professional Edition, of their Virtual Moon Atlas (VMA), software. The Pro Edition of VMA includes a database program - Datlun - that includes geologic era coding for about 2,800 out of approximately 7,800 nearside features. It was felt that the supplemental reference provided here that covers the same subject matter would have addition educational value to lunar enthusiasts, local astronomy clubs, and school children.

As a boy, I was always attracted to looking at the Moon as a giant three-dimensional map illustrating mountain ranges, valleys, bays, headlands and caldera-like craters. In the modern era, we take aerial and space-based photography of Earth features and detailed U.S.G.S. quadrangle maps - leading aids for visualizing the Earth's geological features - for granted. Before the invention of the airplane and computerized map-making, the Moon was the most easily accessible visualizations of aerial views of such features.

Before the Moon became physically accessible during the Apollo and Soviet Luna exploration era, whether the features of the Moon were created by volcanic or meteor impact processes remained an open question. The principle scientific achievement of the Apollo era was to demonstrate virtually all features on the Moon are of meteor impact orientation.

Today, the beginner looking at the Moon, particularly at the southern highlands, sees an apparent jumble of disorganized, random craters in varying degrees of ruin. There also is some apparent structure to Moon's nearside surface - easily seen in its round mares surrounded by towering mountain ranges. There is a structure and geologic story to face of the nearside Moon. Understanding that structure and how it was created can increase one's appreciation of the Moon and aid in locating and understanding its major structural and aesthetic star party showcase features.

When looking at linked figures and images in this document, in some browers, it may be necessary to click the image a second time in order to view a readable high resolution image. In Microsoft Internet Explorer, a second higher resolution image is available, if after the first click, an image opens that displays a plus sign when the mouse is hovered over the image.

Lunar Geologic Eras

The Earth differs from the Moon in two major qualities. The Earth has plate tectonics; the Moon does not. The Earth has a rock-weathering atmosphere; the Moon does not. As a result, the Earth's surface periodically erases its surface record. For the sea-spreading ocean floor, this occurs on a time scale of 100 to 150 million years; for the continental cratons, weathering may take 500 million years to wear away a mountain range. It is fortunate that we have a Moon without plate tectonics or atmospheric weathering because as a consequence of their absence, the Moon reflects a complete record of major solar system meteor bombardments going back about 3.8 billion years - nearly to the creation of the Earth itself.

Those major meteor bombardment eras - with examples of the major lunar features created in each era - are listed in Table 1.

Table 1. Lunar Geologic Eras - Summary | Sort order: Time before present descending
Period Features Begins B year before now Ends B year bef now Chart - Wilhems (1987) ___________ ___________ Features from this era Crater frequency (N per km^2)
Copernican Rayed Fresh Craters 0 1.1 Tycho L006
Tycho 2 L006
Messier A L025
Linne 4km dia.
Bright Copernican Craters near Gassendi
<7.5 x 10^-4 for >1 km craters on mares
Eratosthenian Non-Rayed Fresh Craters 1.1 3.2 Theophilus L008 Marius Hills L042 <7.5 x 10^-4 to <2.5 x 10^-3 for >1 km craters on mares
Imbrian Maria Impact Basins 3.2 3.85 Mare Imbrium
Upper Imbrian 3.2 3.84 Posidonius L020 <2.5 x 10^-3 to <2.2 x 10^-2 for >1 km craters on mares <2.8 x 10^-5 for >20km craters
Lower Imbrian 3.84 3.85 Petavius L016 <2.2 - 4.8 x 10^-2 to <2.2 x 10^-2 for >1 km craters in basins <1.8 - 3.3 x 10^-5 for >20km craters
Nectarian Maria Impact Basins 3.85 3.92 Clavius L009 <2.3 - 8.8 x 10^-5 for >20km craters
pre-Nectarian Terrae 3.92 4.55 Schickard L039 >7.0 x 10^-5 for >20km craters
pre-Imbrian another name including both the Nectarian and pre-Nectarian 3.85 4.55
Era color coding

As can be seen in the preceding table, much of the near-side face of the Moon was reshaped in the lower-Imbrian era by heavy bombardments that created the major nearside mares. (Wilhems 1987, pp. 190, 245, 278).

Aside from the lower Imbrian bombardment, craters on the face of the near-side of the Moon are the result of processes working over geologic time scales and not relatively heavy, short bombardments. Even the heavy higher-rate Nectarian and lower Imbrian bombardments occurred over a one-half billion year period. Figure 2. The cratering rate for each geologic era is shown Figures 1 and 2. For craters larger than 20 kilometers, the present cratering rating is about one-fifth estimated for Imbrian times. For small craters less than 1 kilometer in diameter, the current rate is one-thousandth an estimated Imbrian rate.

Figure 1 - Figure 13.13B, Cratering frequency by time. In Chap. 13 in Wilhems, Don. 1987. A Geologic History of the Moon, USGS Survey Paper 1348

Figure 2 - Figure 8.16, Cratering frequency by time, Nectarian and Imbrian eras. In Chap. 13 in Wilhems, Don. 1987. A Geologic History of the Moon, USGS Survey Paper 1348

The nearside has many large mares; a feature type almost absent from the farside. The farside surface contains a larger percentage of older terrian.

Figure 3 - Apollo 16 photograph AS16-3021 of the lunar farside courtesy of NASA

Figure 4 - Farside lunar geologic map. Plate 12B in Wilhems (1987).

That pattern is probably the result of lunar tidal locking. After creation, the Moon became tidally locked such that the Moon rotates at speed that keeps the same side always pointing towards the Earth. The gravity differential caused the Moon to become egg-shaped and the lunar crust to be thicker (50km) on the farside and thinner (12km) on the nearside. Although both sides of the Moon received large body impacts, on the thinner nearside we see major basin and mare impact structures where lava in the young Moon's mantle could reach the surface through impact-related fractures in the lunar crust.

Impact basins and nearside lunar structure

Figure 5 - Plate 5A,
Structural Features [Nearside]
from Wilhems (1987)

That almost all lunar features are the result of basin impact processes and not volcanism was the principle scientific result of the Apollo era explorations. In the basin impact paradigm, small planetesimals spiraled into the early Moon's surface and impacted at a very low-angle, probably less than 45 degrees but more than 15 degrees. Wood, Modern Moon at 94. (Meteors that impact at less than 45 degrees being to form increasingly non-spherical craters. Wood at 93.) As a consequence, most of the major nearside mares are all slightly elliptical and are not circular.

Upon impact, the early Moon's crust is fractured, circular mountain ranges and circular impact fractures were created around the boundaries of mares and tangent to the impact center. Basalt from the Moon's then molten interior flooded out. Rising magma caused the center of the newly formed mares of the impact basins to rise. As they partially cooled, the mares collapsed. This caused pre-existing large craters on the rim of the impact zone to tilt towards the center of the impact. With sufficient tilting, mare lava could overtop and/or breach the crater rim, thus, flooding the pre-existing crater's floor with mare lava. Alternatively, subsurface heating of the lunar crust from the basin-sized impact could underflow beneath the crater and rise through a now impact-fractured pre-existing crater floor. As these newly flooded and crater floors cooled, their now mare-like flat crater floors fractured. Large scale cooling fractures at the rim boundary create rille systems that are tangent to the impact center of the mare. Within the mares, cooling stresses and submerged impact structures caused wrinkle ridges, straight faults and rilles to form on mare surfaces. During the cooling process, sheet lava would flow from straight rilles or from small craters. At some of the vent points, lava flowed through sinuous rilles.

The basin impact model explains the distribution of rilles and wrinkle ridges mapped by Wilhems in Figure 5. Images of specific lunar features that illustrate these key impact related structures are listed the following table:

Table 2. Basin impact associated structural features
Mare in impact basinEraRükl L100Basin ring remnantRükl L100Tilted crater on mare edgeRükl L100Rille system tangent to basin ringRükl L100
CrisiumNectarian 25, 26, 37, 38 L010Dorsum Oppel
Geminus Ring
[Montes Wasatch]*
Yerkes 26,37
Serenitatis Imbrian13, 14, 23, 24 Posidonius14 L013Rimae Sulpicius Gallus
Rima Menelaus
Tranquilitatis Imbrian35, 36, 37, 45, 46, 47Mare ridges near Lamont35Julius Caesar34Rima Sosigenes35
Fecunditatis Pre-Necatarian48, 49, 37, 59Gutenburg 48Rima Goclenius48
Nectaris Nectarian47, 58Rupes Altai
Rheita Valley (large secondary impact chain)
57 L007
68 L058
Fracatorius58 L021Rima Fracatorius58 L021
Imbrium Imbrian9, 10, 11, 12, 19, 20, 21, 22Mons Archimedes (inner Imbrium ring)
Dorsum Zirkel
Sinus Iridum10
NubiumImbrian53, 54Pitatus54, 64 L084Rupes Recta (Straight Wall)
Rima Hesiodus
54 L015
Humorum Nectarian50, 51Unnamed wrinkle ridges in Mare Humorum52Gassendi
52 L013Rimae Hippalus52, 53
Orientale Imbrian39, 50, VII L020Mons Cordillera
Mons Rook
39, VII

One type of feature, the distribution of which is not fully explained by the basin impact theory, is lunar domes. Wood, Modern Moon at 62-63. Domes are small volcano-like features generally less than 500 meters tall that are believed to be similar to lava domes or shield volcanoes on the Earth. Examples of these features are provided in Table 3 in the following section. Westfall (2000) (at 54) feels at least the larger domes fields, like the Hortensius Domes, appear to be distributed clustered around the edges of the mares.

Feature Types - Lunar Morphology with Earth Analogues

"Analogue morphology" means for the purposes of the following table, landforms that are similar in appearance, but not necessarily created by the same geologic process. Analogies are different from homologies that are both similar in appearance and cause. For example, a pit and rille on the Moon may be caused by a small meteor impact and subsequent subsurface melting. On Earth, a similar landform may be caused by a small volcano. On the Moon, a long scarp like Rupes Altai is associated with a large basin impact; on the Earth, a scarp like the Niagra Escarpment is associated with geochemical processes. In general, the geologic processes that form lunar features are not the same forces that create similar terrestrial landforms.

While the comparative appreciation of the morphology of Earth and lunar features is instructive, care should not be taken to attribute volcanic causation to many lunar features. That almost all lunar features are the result of basin impact processes was the hard-won knowledge result of the Apollo program. For essays about the pre-Apollo views on the Moon, see Fielder (1961). In this regard, the following table of lunar features provides a science education launch point to discuss basic logical reasoning regarding proof of causation.

Table 3. Feature Types - Examples and Earth Analogue Morphology
Sort order: Name ascending

Term (singular/plural) Latin for Example Rükl Earth Analogue
Albedo High surface contrast area Reiner Gamma L057 28
Albedo - peak shadow High surface contrast area Central peak Alphonsus 44 Mauna Kea, Hawaii shadow
Albedo - bright peak reflection High surface contrast area Montes Recti 11 Vinson Massif, Anarctica
Albedo - terminator High surface contrast area 27 Day-old Moon 44 Earth terminator
Basin Geologic depression, a landform lower than the surrounding area Mare Orientale L020
Mare Orientale #2
Schiller-Zucchius basin L059 L059 #2
39, 50, VII
70, 71
Vredefort crater, South Africa (250-300km dia)
Catena, catenae Chain of secondary craters from larger impact Catena Davy L051 42 Aorounga Crater, Chad
Crater, craters Circular or oval depression Copernicus L005
31, 30 Barringer Crater [Meteor Crater, Arizona] Upheaval Dome, Canyonlands National Park, Utah (possible)
Simple Bessel

Complex Aristoteles

Concentric Hesiodus A
Louville D
Quarkziz Crater, Algeria
Oblique impact Messier A L025
Proclus L012
48, 26
Elongate Schiller L030 62, 71
Slumped walls Copernicus L005 31 Isla Isabella Volcano
Scalloped (partially failed rim, arc collapse) Triesnecker
33, 20
Polygonal plan Gambart 32
Ruined Prinz
Lambert R
Ray, rays, bright rayed craters Tycho rays

Radial banded Brayley, Masetlin and Encke E, Marius A 19, 29
Dark halo Alphonsus small floor craters L047 (inactive, possible volcanic origin)
Alphonsus #2
44 Acsension Island cinder cones
Crater, central peak Well-defined Arzachel Arzachel #2 Tycho L006 55, 64
Ruined Maurolycus 66
Domed Römer Alpetragius 25, 55
Crater, floors Flooded floor, mare-like Plato L052 3, 4
Ring dike Atlas 15 Richat Ring Dike, Mauritania, Africa
Fractured floor, irregular rille Gassendi L013 52
Fractured floor, circular rille Taruntius L037 37
Fractured floor, polygonal rille Lavoisier H 8, VIII
Fractured floor, radial rille Petavius L016 Humboldt Petavius #2 59, 60, IV
Complex melt Lambert 20
Inudated Prinz 19
Debris-strewn Hansteen 40
Debris, hommocky Gärtner
W. Bond
Annular (concentric) Hesiodus A

Dark floor Hercules 14
Flat floor (straight bisecting floor shadows) Grimaldi 39
Domed floor (convex bisecting floor shadow) Mersenius L044 40
Satellite feature(s) Satellite craters named with suffix letters ordered by degradation; sometimes includes domes with Greek letters Crozier H
Marius A, B & C
48 , 29 Barringer Crater [Meteor Crater, Arizona]
Domes, dome Lava dome Hortensius Domes L065
Hortensius Domes L065 #2
Mons Gruithuisen domes L49
30, 9 Katmai Volcano Dome in Alaska
Long Valley Caldera and Volcanic Domes
Lava Dome in Mt. St. Helens cauldera from space
Dorsum, dorsa Ridge; wrinkle-ridge usually found on mare Dorsum Zirkel
Mare Nubium dorsum
20, 53, 54 Lava Pressure Ridge on Snake River Plan
Undara, Queensland, Australia Volcanic Tube
Fossa, fossae Long-narrow depression Rimae Mersenius
[Alphonsus line]*
Fossa Cauchy L048
36, 43-44, 39 Slot Vent, Big Southern Butte, Snake River Plain, Idaho
Graben Depressed block bordered by parallel faults; German for "ditch" Alpine Valley L019
Sirsalis Rille
4, 50 Afar Depression, Ethiopia
Death Valley, California
Basin and Range province, Utah and Nevada
Lacus Lake Lacus Excellentiae 62
Lava flows Hardened sheets of lava Imbrium lava flows L098
Lava flow on Mare Imbrium
10, 11, 20, 21 Craters of Moon, Idaho lava flows
Snake River Plain Basaltic Flow
Snake River Plain Basaltic Flow - false colors
Mauna Loa Lava Flows
Newberry Caldera Lava Flow, Oregon
Mare, maria Seas Mare Serenitatis
Mare Serenitatis #2
13, 14, 23, 24 Snake River Plain Basaltic Flow
Massif - sharp Mountain isolated on a plain or mare Mons Piton 40 Vinson Massif, Anarctica
Massif - flat Mountain isolated on a plain or mare Mons Hansteen
Mons Maraldi
12, 25 Uluru (Ayers Rock), Australia
Brandberg Massif, Namibia
Mons, montes Mountains [Montes Wasatch]*
Montes Caucasus
26, 13 Wasatch Mtns, Utah
Alps, Europe
Oceanus Ocean; large mare Oceanus Procellarum L095 8, 17,18, 19, 28, 29, 30,39, 40, 41 Snake River Plain Basaltic Flow
Deccan Plateau and Deccan Lava Traps (Permian lava plain, now eroded)
Palus, paludes Marsh Palus Putredinis 22
Planitia, planitiae Plain Planitia Descensus 28
Promontorium, promontoria Cape or headland; usually on mare Promontorium Laplace
Promontorium Heraclides
10, 10 Rock of Gibraltar - Pillars of Hercules
Rille - sinuous
Rima, rimae (same as rille)
Long, sinuous narrow valley on the surface of the moon Hadley Rille L066
Rima Marius L074
Rima Birt
22, 18, 54 Bear Crater, Snake River Plain, Idaho
Pit Crater and Collapsed Lava Tube, Snake River Plain, Idaho
Before collapse: Ape Cave lava tube interior, Washington Lava River Tube interior, Bend, Oregon
Rille - Rilles-arcuate
Rima, rimae (same as rille)
Curved fissure surface of the moon Sulpicius Gallus Rilles 23
Rille - straight
Rima, rimae (same as rille)
Straight fissure on the surface of a planet or moon Triesnecker Rilles L035 33 Snake River Plain Straight Rift with Cinder Cone
Mauna Loa fissure eruption
Christmas Valley graben fissure, Oregon
Rupe; rupes Cliff; scarp; escarpment or wall Rupes Recta (Straight Wall) L015
Rupes Altai L007
54, 57 Darling Scarp, Perth, Australia
Cocks Comb Ridge, Utah
Niagra Falls Escarpment
Arabian Peninsula Escarpment
Sinus Bay Sinus Iridum L014 10 False Bay, Capetown, South Africa False Bay #2
Carpentaria Bay, Austrialia
Terrae, Terra Lighter colored highlands (no longer IAU sanctioned) Terra Fertilitatis
Pre-Necatrian (oldest) terrain on the Moon)
55, 65-66, 73-75 North American craton (oldest terrain in North America)
Vallis, valles Valley Rheita Valley L058
Vallis Snellius
68, 59
Volcano - caldera Landform generated by the eruption of magma Crüger L052 (possible volcanic caldera) 50 Kilauea Caldera, Hawaii
Volcano - shield Landform generated by the eruption of magma Rümker L062 (large dome with multiple small domes on top) 8 Big Island, Hawaii (shield volcano, multiple lava tubes)
Cinder cones and domes on plain beside Newberry Caldera, Oregon
Statio Station, or surveyed location, as in a landing site of an exploration mission. Statio Tranquillitatis
Apollo 11 landing site
35 Prime Meridian at the Royal Observatory at Greenwich, England
Other Mascons - high gravity zones Nearside mascons Gravitational anomalies in Earth's field from GRACE satellite
Other Volcanic lava field Ina D L099 (possible, inactive) 22 Phlegarean Fields (Campi Flegrei), Naples, Italy (active)
Other Dyke Sirsalis Rille 50 Great Dyke, Zimbabwe

* - Not IAU sanctioned names. Informal feature names suggested by C. Wood.

Geologic era of specific features

Using the USGS-NASA Geologic Atlas charts and era assignments in Wilhems' Geologic History of the Moon, geologic eras were assigned to 835 lunar features. Tables sorted by name and lunar latitude and longitude are provided. The "Table of Features with Geologic Eras by Lunar Latitude and Longitude" can be imported into a spreadsheet, like Microsoft Excel. In Microsoft Excel, simply paste the url of the table into the "Open | File" dialogue. Excel's sort ( Data | Sort ) and/or auto-data filter feature ( Data | Filter | Autofilter ) can be used to drill-down to those features that are near the lunar terminator on a particular night. Using such a spreadsheet and once the longitude of the lunar terminator is known, star party tours by lunar geologic eras can be quickly created for a particular night.

Color of the Moon

The Moon has color; we just do not see them because the reflected light of the Moon is too dim to trigger color receptors in the human eye. (At night during the full Moon, you see objects in black-and-white.) A film or digital camera accumulates sufficient light to trigger color sensors on film or on the electronic receptor of a digital camera - as seen in the following LPOD images:

The color and brightness of the surface of the Moon is a result of its chemical composition and fading caused by micro-meteor bombardment over a geologic time scale.

Relatively fresh craters - Copernican craters that are "only" less then a billion years old - are surrounded by bright ejecta rays. The high reflectance - or albedo - of these rays is the result of the glass crystalline content of the ejected material and the chemical composition of underlying mare bedrock. Fresh bedrock material is dispersed by a meteor's impact and the shock of the impact turns a portion of the bedrock into a crystalline glass. This crystalline glass has a high albedo. The bedrock typically is covered by a 5 or 6 meter layer of darker lunar soil - called regolith - which has a lower content of crystalline glass and a lower albedo. Wilhems (1987) at 95.

Micro-meteors and the harsh space environment transform this fresh bedrock and its high-reflectance crystalline glass into darker regolith. Today, the Moon is continually bombarded by small meteorites and meteorite sand grains, as recently popularized by reports regarding a Nov. 7, 2005 and a May 2, 2006 meteor impact on the Moon captured by Earth-based NASA robotic patroller telescopes at the Marshall Space Flight Center. Such small impacts have been regularly captured for many years by amateurs, including by members of the Meteoritic Impact Search Program of the Lunar Section of the Association of Lunar and Planetary Observers (ALPO). One result of this continual micobombardment is the creation of the fine powdery lunar soil - the regolith - seen in a famous photograph of Buz Aldrin's first bootprint on the surface of the Moon. The continual microbombardment churns the lunar surface soil causing changes in its chemical composition and brightness. A second result of continual micrometer bombardment is the gradual fading of bright crater rays as seen surrounding the crater Tycho.

The broad-scale colors seen on the Moon's surface in Filipe Alves's image of the Moon - the blue mares and the orange and orange-reddish highlands - are the result of chemical composition of the underlying source materials and the relative fraction of titanium, aluminum and iron in each region.

Figure 6 - Courtesy of NASA. Apollo 11 bootprint on the Moon

Table 4. Summary of colors and spectral types from Wilhems (1987) (pp. 96-99)
Color Description
Blue"Ti-rich, spectrally blue lavas form at least half of Mare Tranquillitatis, the adjoining border of Serenitatis, the lobate flows of Mare Imbrium, central Mare Humorum, and much of Oceanus Procellarum. . . .."
Red ."Red spectral classes, thought to be lowest in Ti content, are concentrated in Lacus Somniorum, Mare Frigoris, Sinus Roris, and northern Mare Imbrium; that is, they occur in diverse settings over the north half of the Procellarum basin.."
Red - mISP "Red spectral class mISP forms extensive areas in central Serenitatis and the outer trough of western Procellarum.."
Orange "Class hDWA occurs at several mare margins and fills most of Mare Vaporum. On the color-difference photographs, its color appears to be intermediate between red and blue and has been called 'orange' . . .""
Orange-red - mIG "Orange or (partly) red spectral class mIG- covers much of the area west of the central meridian and south of the strong blue-red association in Mare Imbrium. Apollo 12 landed within this belt. This class also forms much of Mare Crisium and Mare Fecunditatis. . . . . Orange spectral classes mBG-, characteristic of Mare Nectaris, and LBG-, common among the northern very red units, also are probably Al-rich. . . . . One interpretation of the orbital geochemistry is that Maria Smythii, Fecunditatis, and Crisium are all Al-rich. . . . "

Figure 7 - Table 5.1, Remotely Sensed Properties of Mare Units. In Color, Chap. 5 (pp. 96-99) in Wilhems, Don. 1987. A Geologic History of the Moon, USGS Survey Paper 1348

All of these chemical changes occur in an oxygen-free space environment. Apollo astronauts report that once back in their lander module, fresh moon dust has a burnt smell. But after lunar rocks are returned to the Earth, they are odorless. Although the reason for the smell is not known - one explanation for the smell is that metals and other compounds in the soil oxidize on their first exposure to air.

Use of the USGS-NASA Geologic Charts

Use of the USGS-NASA Geologic Atlas of the Moon is complicated by the dense colors and features on the charts. Not all satellite craters are indicated on the charts. Typically, effective use of these NASA Apollo era lunar geologic charts requires supplemental reference to both a good lunar atlas, like Rükl's Atlas of the Moon and U.S. Air Force-NASA Lunar Aeronautical Charts (LAC). This is particularly true when trying to find smaller craters less than 20 kilometers in diameter.

Chart numbers listed in the "Table of Features with Geologic Eras by Name" and the "Table of Features with Geologic Eras by Lunar Latitude and Longitude", refer to LAC chart numbers and not the geologic chart numbers. An index cross-reference map between the "LAC" chart numbers and the geologic atlas charts is provided at the main LAC page. The duplicate "I" chart numbers for the geologic charts are not listed in the geologic era reference table provided here, since both the LAC and geologic charts cover the same area.

Future exploration

Table 14.2 in Wilhems' Geologic History suggests 18 supplemental sites for sample return missions in order to better calibrate the absolute ages of surface rocks. The sites include the South Pole-Aitken Basin massifs, the Nectarian mare floor, floor melt in Copernicus, a farside mare and the lava dome Gruithuisen gamma. In 2004, NASA announced in its Vision for Space Report a return-to-the-Moon initiative. In 2006, the U.S. National Academy of the Sciences issued a recommendation - the Scientific Context for the Exploration of the Moon Report - that suggested targeted science missions for the NASA return to the Moon program. Recommended activities were similar to Wilhems' 1987 recommendations: (1) return a sample from the South-Aitken Basin, (2) maximize the diversity of lunar samples, filling in rock sample gaps from the Apollo era explorations, and (3) investigation of more recently discovered, potential ice deposits at the lunar poles.

In addition to prior remote sensing missions like Clementine (1994), Lunar Prospector (1998) and SMART-1 (2006), the following near term (2007-2010) remote sensing missions are planned by the United States, Japan, China and India:

Table 5. Near-term remote sensing missions to the Moon currently in development
YearNameCountryWill do*Mission url
2007SeleneJapanTwo subsatellites with 14 science instruments will do multispectral and high-resolution imaging to support future missions. [Size of a school bus.]Link
2007?Chang’EChinaObtain lunar surface three-dimensional stereo image; analyze distribution of useful elements and estimate abundance; survey thickness of soil and evaluate resource of He-3.Link
2007/2008Chandrayaan-1 IndiaHigh-resolution remote sensing of the lunar surface features in visible, near infrared, X-ray and low energy gamma ray regions.Link
2008Lunar Reconnaissance OrbiterUnited StatesMoon's radiation environment, map the lunar topography in high-resolution, scan for resources in the polar regions and map the composition of the lunar surface.Link
2010Lunar-AJapanSeismology using penetrators.Link

* - Except as to Lunar Recon. Orbiter, quoted from NASA. 1/24/2005. International Participation in Lunar Exploration. (Slide Presentation).


Wilhems (1987) was reviewed and a table of approximately 190 lunar geologic eras assigned to lunar features was created. The USGS-NASA Geologic Atlas of the Moon charts were reviewed and the geologic eras for approximately 645 features were extracted and added to a reference table containing a total of 835 lunar features.

The reference table codes from the USGS-NASA Geologic Atlas charts are based on the geologic eras assigned in those pre-Apollo exploration charts. In the early 1960's Geologic Atlas charts, the Pre-Nectarian and Nectarian eras are combined into one era - the Pre-Imbrian. Based on later Apollo exploration lunar sample returns, the Pre-Imbrian era was later subdivided in Wilhems (1987) into the Pre-Nectarian and the Nectarian eras.

In the reference table provided here, all geologic era assignments extracted from the Geologic Atlas charts for the upper and lower Imbrian eras were assigned a single group coding - the Imbrian era.

This review and extraction process occurred during October and November 2006. On November 6, 2006, Christian Legrand and Patrick Chevalley issued Version 3.5, Professional Edition, of their Virtual Moon Atlas (VMA), software. The Pro Edition of VMA includes a database program - Datlun - described above. Since this project was substantially completed, it was decided to distribute it for its supplemental educational value to lunar enthusiasts.


This note is amateur astronomer work product. Corrections to any errors are welcomed and appreciated.

References and further reading:

When purchasing any used or new books on this list through Amazon, using the Amazon link at Dr. Charles Wood's Lunar Picture of the Day (LPOD) contributes part of the purchase price to supporting the LPOD website.

Revision history

Content-Child Safe Ratings

Site tracking


No copyright is claimed as to any original materials on this web document. All original content by this author is released to the public domain.

This website makes extensive use of external content links, particularly to Dr. Charles Wood's LPOD site and to individual amateur images incorporated at the LPOD site that are subject to copyright protection. No claim to copyright is made as to these linked external sources or any other external linked reference source. All external, linked reference sources are identified by hover boxes labeled "Click to link to external content".

This website incorporates several reproductions of plates and graphs from Wilhems' 1987 Geologic History book. That publication was prepared by the U.S. Geological Service and as a publication of the United States is not subject to copyright and is part of the public domain.

Linking to M. Clark's Whitepeak Observatory images of terresterial features is by permission.

Prepared by K. Fisher Rev. 12/26/2006