WHAT DID WE LEARN ABOUT THE MOON

FROM THE APOLLO PROGRAM?

WHAT DID WE LEARN ABOUT THE MOON

FROM THE APOLLO PROGRAM?

* Lifeless — no life, no fossils, no organic chemicals.

* Chemically similar to Earth, but significantly different in details: It has no indigenous water, is 

poor in volatile elements (readily vaporized).

* Preserves effects of catastrophic early meteorite bombardment — common to all terrestrial 

planets, including Earth, but traces no longer preserved on active planets like Earth.

* Not uniform throughout; is divided (like Earth) into outer crust, inner mantle, (possible?) small 

metal core.

* Globally asymmetric (slightly egg-shaped); thicker crust on farside, most maria deposits (lava 

flows) on nearside.

* Has no magnetic field, little or no metallic core like Earth’s, but “fossil” magnetism is preserved 

in lunar rocks; this is still a mystery. 

* Large-scale (100–1000 kilometers) unexplained magnetic anomalies preserved on lunar surface.

* Lunar surface covered by powdery layer (“lunar soil” or regolith), produced by shattering of 

bedrock by prolonged meteorite bombardment.

* History of Sun and cosmic rays determined from actual atoms of Sun and stars trapped in lunar 

rocks and soil.

* Unexplained concentrations of nitrogen isotopes detected in ancient solar wind trapped in lunar 

regolith.

* Pre-Apollo hypotheses about lunar origins shown to be inadequate. 

Scientists now believe that the Moon formed as a result of a collision between early Earth and a Marssized planet. This smaller planet was destroyed in the collision, which took place about 4.5 billion years 

ago. The giant impact sprayed vaporized material into a disk that orbited Earth. This vapor later cooled 

into droplets that coalesced into the Moon.

* Not primordial — it is an evolved 

terrestrial planet.

* Ancient — it still preserves an early 

history (the first billion years), 

which must be common to all 

terrestrial planets.

* Shows evidence for wholesale 

primordial melting, formation of 

outer “magma ocean”-large-scale 

chemical separations within Moon; 

traces still remain in lunar rocks.

* Dark lunar maria (“seas”) and lightcolored highlands made of 

chemically and mineralogically 

different rocks.

* Maria made of dark volcanic lavas 

(basalts) poured out in huge 

volcanic eruptions 3–4 billion years 

ago.
TOP TEN SCIENTIFIC DISCOVERIES MADE

DURING APOLLO EXPLORATION OF THE MOON

TOP TEN SCIENTIFIC DISCOVERIES MADE 

DURING APOLLO EXPLORATION OF THE MOON

1. The Moon is not a primordial object; it is an evolved terrestrial planet with internal zoning 

similar to that of Earth.

2. The Moon is ancient and still preserves an early history (the first billion years) that must be 

common to all terrestrial planets.

 The extensive record of meteorite craters on the Moon, when calibrated using absolute ages of rock 

samples, provides a key for unraveling timescales for the geologic evolution of Mercury, Venus, and Mars 

based on their individual crater records. Photogeologic interpretation of other planets is based largely on 

lessons learned from the Moon. Before Apollo, however, the origin of lunar impact craters was not fully 

understood and the origin of similar craters on Earth was highly debated. 



3. The youngest Moon rocks are virtually as old as the oldest Earth rocks. The earliest processes 

and events that probably affected both planetary bodies can now only be found on the Moon. 

 Moon rock ages range from about 3.2 billion years in the maria (dark, low basins) to about 4.5 billion 

years in the terrae (light, rugged highlands). Active geologic forces, including plate tectonics and erosion, 

continuously repave the oldest surfaces on Earth, whereas old surfaces persist with little disturbance on 

the Moon. 

4. The Moon and Earth are genetically related and formed from different proportions of a 

common reservoir of materials. 

 Oxygen isotope compositions of Moon rocks and Earth rocks clearly show common ancestry. Relative 

to Earth, however, the Moon was highly depleted in iron and in volatile elements that are needed to 

form atmospheric gases and water. 

5. The Moon is lifeless; it contains no living organisms, fossils, or native organic compounds. 

 Extensive testing revealed no evidence for life, past or present, among the lunar samples. Even nonbiological organic compounds are amazingly absent; traces can be attributed to contamination by 

meteorites. 

Before Apollo, the state of the Moon was a subject of 

almost unlimited speculation. We now know that the 

Moon is made of rocky material that has been 

variously melted, erupted through volcanos, and 

crushed by meteorite impacts. The Moon possesses a 

thick crust (60 km), a fairly uniform rigid lithosphere 

(60–1000 km), and a partly liquid, plastic asthenosphere (1000–1740 km); a small iron core at the 

bottom of the asthenosphere is possible but 

unconfirmed. Some rocks give hints for ancient 

magnetic fields although no planetary field exists 

today.
6. All Moon rocks originated through high-temperature processes with little or no involvement 

with water. They are roughly divisible into three types: basalts, anorthosites, and breccias. 

7. Early in its history, the Moon was melted to great depths to form a “magma ocean.” The lunar 

highlands contain the remnants of early, low density rocks that floated to the surface of the 

magma ocean. 

8. The lunar magma ocean was followed by a series of huge asteroid impacts that created basins 

that were later filled by lava flows. 

 The large, dark basins such as Mare Imbrium are gigantic impact craters, formed early in lunar history, 

that were later filled by lava flows about 3.2–3.9 billion years ago. Lunar volcanism occurred mostly as 

lava floods that spread horizontally; volcanic fire fountains produced deposits of orange and emeraldgreen glass beads. 

9. The Moon is slightly asymmetrical in bulk form, possibly as a consequence of its evolution 

under Earth’s gravitational influence. Its crust is thicker on the farside, while most volcanic 

basins — and unusual mass concentrations — occur on the nearside. 

 Mass is not distributed uniformly inside the Moon. Large mass concentrations (“mascons”) lie beneath 

the surface of many large lunar basins and probably represent thick accumulations of dense lava. 

Relative to its geometric center, the Moon’s center of mass is displaced toward Earth by several 

kilometers. 

10. The surface of the Moon is covered by a rubble pile of rock fragments and dust, called the 

lunar regolith, that contains a unique radiation history of the Sun, which is of importance to 

understanding climate changes on Earth. 

 The regolith was produced by innumerable meteorite impacts through geologic time. Surface rocks and 

mineral grains are distinctively enriched in chemical elements and isotopes implanted by solar radiation. 

As such, the Moon has recorded 4 billion years of the Sun’s history to a degree of completeness that we 

are unlikely to find elsewhere. 

Basalts are dark lava rocks that fill mare basins; they generally 

resemble, but are much older than, lavas that comprise the 

oceanic crust of Earth. Anorthosites are light rocks that form 

the ancient highlands; they generally resemble, but are much 

older than, the most ancient rocks on Earth. Breccias are 

composite rocks formed from all other rock types through 

crushing, mixing, and melting during meteorite impacts. The 

Moon has no sandstones, shales, or limestones such as testify 

to the importance of water-borne processes on Earth.

The lunar highlands were formed about 4.4–4.5 billion years 

ago by flotation of an early, feldspar-rich crust on a magma 

ocean that covered the Moon to a depth of many tens of 

kilometers or more. Innumerable meteorite impacts through 

geologic time reduced much of the ancient crust to curved 

mountain ranges between basins. 

Lunar sample 70035

Lunar sample 15415
A regional map showing important geologic features like faults, folds, and channels is called a geologic map. Geologic maps 

also show surface geologic units, or groups of rocks with the same definite characteristics that you can see, feel, smell, or 

measure. A geologic unit is shown on a geologic map with a particular color. The boundary between different geologic units, 

shown on a geologic map as a thin, solid line, is called a contact.

The basic history of how the geologic units in an area were formed and what happened to them over time is called its 

geologic history. Decoding the geologic history of an area from an overhead photograph or a geologic map requires you to 

use two simple rules:

Principle of superposition — This deals with a geologic unit that formed without disturbing the features around it 

(for instance, lava flows or sediment deposits). This rule simply states that whatever unit lies on top of (or superposes) 

other units is the youngest unit. In other words, the bottom unit had to be there first in order for a younger unit to form 

on top of it.

Principle of cross-cutting relations — This deals with the special situation of structures that disrupt geologic units, 

such as faults and channels. The structures are younger than the units they disrupt (or cross-cut).

GEOLOGY OF THE MOON

second). These impact craters provide an important tool for determining the relative ages of different deposits: For a given 

area, older deposits have more impact craters on them, and younger deposits have fewer impact craters. The number of 

craters in an area of specified size is called crater density; thus, older deposits have a higher crater density than younger 

deposits.

We recognize geologic units on the Moon using properties we can observe or measure from pictures, including 

brightness, smoothness or hilliness, and crater density. The nearside of the Moon contains two very basic geologic 

units. Look carefully at Fig. 1 to see two distinct units. List the characteristics of the units. When you’re finished, 

give each unit a name that you feel is appropriate based on its characteristics.

The two basic units that you just identified have been known since Galileo first looked at the Moon through a very lowpower telescope in 1609. He called the light-colored, hilly, heavily cratered unit terra, which is Latin for “land.” The dark, 

smooth, less-cratered plains are called maria (singular mare), which is Latin for “seas,” because their smoothness led some 

early astronomers to think they were the surfaces of lunar oceans.

ACTIVITY 1: GEOLOGIC MAPPING AND

THE GEOLOGY OF THE MOON

ACTIVITY 1: GEOLOGIC MAPPING AND

THE GEOLOGY OF THE MOON

Figure 1 shows a photograph of the northwest (upper left) part of the 

nearside of the Moon. Note the dark-colored, circular feature that fills 

most of the photograph. Apollo 15 landed in the extreme southeast 

corner of this feature in 1971.

Apollo missions landed at only six different sites on the Moon. For 

this reason, you might think that very little is known about the Moon’s 

geology. But this isn’t true! The pictures of the Moon returned by 

spacecraft, and even taken through telescopes, contain a great deal of 

information about the Moon’s geology. Studying geology using 

pictures is called photogeology. It is different from studying geology on 

the ground, because all the observations you make about a surface 

come from looking at it from a distance.

There are many kinds of surface features in Fig. 1, but they can be 

lumped into two big classes. Brightness features are regions that stand out 

from their surroundings because of a brighter or darker color, 

generally caused by a difference in the amounts of light-colored and 

dark-colored minerals in rocks on the surface. Differences in 

brightness can also be caused by shadows, so you have to be careful in 

recognizing brightness features. The most common landforms on the 

Moon are called impact craters. These are circular, raised-rimmed 

depressions formed by explosions that occur when comets and 

asteroids collide with the Moon at high velocity (about 12 miles per Fig. 1.
You identified the mare and terra units 

photogeologically. That is, you have 

defined and mapped units based on what 

you can see in a black-and-white photograph. From what you have done so far, 

can you say what types of rock the units 

are made of? Why or why not?

Figure 2 shows an enlarged, highresolution photograph of part of the 

region shown in Fig. 1. Cover it with 

clear plastic. This region is immediately 

around the Apollo 15 landing site, and 

has the same two major units you 

identified previously. On the plastic 

overlay, trace the units’ contact. There 

are a number of indicators of whether 

one unit is superposed on another unit. 

One of these indicators is called an 

embayment relation. This occurs when a 

unit is deposited in fluid form, for 

instance, as lava flows or as sediment 

that settles out of water. In this case, the 

younger unit embays the older unit; in 

other words, it fills in low spots of the 

older unit at the contact. When one 

feature embays another it often looks 

like the water of a bay flowing around 

land features, and this is where the term 

embay comes from. Look carefully at the 

contact between the mare and terra for 

an embayment relation. On this basis, 

which unit (mare or terra) is younger? 

Why?

Now look at the number of craters on 

each of the two units. Do the crater 

densities show the same relative ages of 

the mare and terra as you just determined? If not, can you think of a 

possible reason why?

The major structure in this photograph is the curvy trough, called Rima Hadley (or in English, Hadley Rille). Trace it on the 

plastic overlay. What would you call this structure?

What are the relative ages of the mare and Rima Hadley? What principle did you use to recognize this age relation?

Look at the large, round impact crater alongside Rima Hadley. This is Hadley Crater. What are the relative ages of Hadley Crater 

and Rima Hadley? Why?

Now, reconstruct the geologic history of the area surrounding Rima Hadley by numbering the units and structures in the order 

in which they formed: Hadley Crater, Mare, Terra, Rima Hadley.

Based on everything you’ve learned about the mare, what kind of rock do you think it might be (lava flows, sediments, coal, 

etc.)? What is necessary for you to know for sure?

Look at the slightly brighter region of mare away from the contact with the terra. This region contains an abundance of very 

small craters with noncircular shapes. Compare and contrast their appearance (size, shape, and relief) with that of Hadley Crater 

by listing their similarities and differences. Are these unusual craters older or younger than the mare? Why?

How might the origin of the unusual craters have differed from the origin of Hadley Crater? Can you think of a process that 

could have formed them?

Fig. 2.
ACTIVITY 2: IMPACT CRATERING AND

RAINY DAY CRATERING

ACTIVITY 2: IMPACT CRATERING AND

RAINY DAY CRATERING

Impact Craters

a layer of fine, contrasting powder: different sand, tempera paint powder, or colored sugar work well. 

Cover this layer with about a few millimeters of sand. Then throw marbles or gravel into the sand, and 

see if your craters excavate the contrasting layer. How deep is your crater? How far was the contrasting powder 

thrown by the impact? This experiment can be expanded and quantified by experiments with different 

types of sand, different depths of burial, marbles of different sizes and weights, and different heights 

and angles of impact. Using a slingshot to shoot the marble will permit higher velocity impacts and 

bigger craters, but careful supervision is required. Be sure to wear eye protection.

Rainy Day Cratering

This activity allows students to learn how planetary surfaces are modified by multiple impacts over 

time and how surfaces can be dated by the analysis of craters. As the number of impact craters 

increases on a surface, the appearance of the surface changes. After a period of time, equilibrium is 

reached, in which old craters are destroyed as quickly as new craters form. This is what has happened 

on the Moon.

Place a piece of duct tape over the end of a watering can. Using a pin, poke one or two holes in the 

tape. Fill the can with water, but don’t make it too heavy to hold for long periods of time. Fill four pie 

pans with fine sand. Place one pan on the floor on top of a drop cloth or newspaper. Pour the water 

from the can very slowly through a mesh screen onto the sand. The mesh screen will break up the 

drops into smaller drops. Move the screen around so the water hits dry screen as much as possible. 

Rain on the pan for about 5 seconds until several craters have formed. How do the crater sizes vary? Are 

they clustered together? Do they overlap? Make a crater with your finger in the second dish. Place this dish in 

the rain for 30 seconds. What does this surface look like? What happened to the large crater you formed? Are there 

more overlapping craters than in the first pan? Make another finger crater in each of the other two pans and 

rain on each of them for two and four minutes respectively, remembering to pour the water slowly. 

What happend to the large crater you formed in the last two pans? Is there a marked difference between the two pans, 

allowing you to tell which pan spent the most time in the rain?

When meteorites strike the Moon’s surface, they 

leave impact craters. During a meteorite impact, 

rocks from deep inside are gouged up and thrown 

onto the surface, so impact craters can be used to 

show us rocks from underground. Also, the 

abundance of impact craters on a surface shows 

its age — the more craters on a surface, the older 

it must be.

Start with a flat sand surface. A playground 

sandbox is ideal, but any unbreakable box with a 

surface bigger than about 2 feet by 2 feet will do. 

Smooth the sand surface, and cover the sand with 
WHAT DID WE LEARN ABOUT THE MOON

FROM CLEMENTINE AND LUNAR PROSPECTOR?

WHAT DID WE LEARN ABOUT THE MOON

FROM CLEMENTINE AND LUNAR PROSPECTOR?

* Work to understand the data returned from two recent unmanned missions (Clementine, 1994; Lunar 

Prospector, 1998) is ongoing. However, we do have new knowledge about the Moon and some firstorder conclusions from these two missions. 

The Global Surface Composition of the Moon

* Crust is highly enriched in aluminum on a global basis, supporting its origin by early global melting (the 

magma ocean).

* Incompatible trace elements (i.e., those that do not go easily into rock-forming minerals) are 

concentrated within an elliptical zone on the western nearside (the Imbrium-Procellarum region).

* Magnesium- and iron-rich zones are found within the lunar highlands; these zones are usually associated 

with large impact basins.

* Mare basalts rich in titanium (returned in abundance by the Apollo 11 and 17 missions) are rare in the 

global mare lava inventory.

The Topography of the Moon

* The Moon displays an enormous range of global relief (16 kilometers), as big a range as the more active 

and diverse Earth.

* The dominant cause of high relief on the Moon is the presence of large, multi-ring impact basins.

* Lunar multi-ring basins appear to preserve their original topography for most of geological time.

* The South Pole-Aitken Basin on the farside of the Moon is the largest (2600 kilometers diameter) and 

deepest (over 12 kilometers) impact basin known in the solar system. 

The Internal Structure of the Moon

* The Moon shows many areas of subsurface mass concentrations (mascons) that cause the gravity field of the Moon 

to be very “lumpy,” requiring constant adjustments for 

orbiting spacecraft.

* The mascons are always found beneath the 

floors of large impact basins and probably 

represent plugs of dense, uplifted rocks from

 the lunar mantle.

The Poles of the Moon

* Areas are found near the lunar poles that are 

in permanent darkness; some areas may be in 

permanent sunlight.

* The south pole appears to have more dark area 

than the north pole, mostly as a result of its 

location just inside the rim crest of South PoleAitken Basin.

* Water ice, derived from impacting comets, is 

found in the dark areas near both poles.
PPOSTER OSTER I IMAGE MAGE C CAPTIONS APTIONS

1

2

3

4

5

6

7

8

9

10

1. Apollo 11 Lunar Module Pilot Edwin “Buzz” Aldrin stands on the Moon 

during the first lunar landing mission, July 20, 1969. AS11-40-5903.

2. Map of the iron (Fe) content of the nearside of the Moon, derived from 

Clementine color data. Reds and yellows are areas having high Fe content 

(associated with the dark, Fe-rich mare basalts), while blues and purples 

are zones of low Fe content (associated with the light, rugged highlands).

3. Map of the concentration of the element thorium (Th) on the nearside 

of the Moon derived from Lunar Prospector gamma-ray data. Thorium 

is a trace element that tracks the component KREEP [for potassium (K), 

rare-earth elements (REE), and phosphorus (P)], a remnant of the early 

formation of the lunar crust and mantle. The Lunar Prospector data 

show that Th (and therefore KREEP) is highly concentrated in the 

Oceanus Procellarum region of the western nearside (shown by the red 

and yellow areas). The origin of this unusual material is under study by 

lunar scientists.

4. Maps of the flux of “mid-energy” neutrons (blue = low, red = high) 

over the north (left) and south (right) poles of the Moon from Lunar 

Prospector. Depressions in the number of these neutrons emitted are 

indicative of large amounts of hydrogen in the lunar soil. These maps 

show that such areas are confined to small regions near the poles of the 

Moon, where crater floors are in permanent shadow and it is very cold 

(–220°C, or only about 50°C above absolute zero). These areas contain 

deposits of water ice, derived from impacting comets and water-bearing 

meteorites onto the Moon for the last few billion years.

5. Mosaic of about 650 Clementine images of the south pole of the Moon, 

from 80°S to the pole (center). The nearside of the Moon 

 Moon is the top half of the image; the bottom half is the farside. Mountainous areas at top center are the remnants of the rim of the 

enormous South Pole-Aitkin Basin, an impact crater 2500 km in diameter. Large parts of this area (about 15,000 km2 ) are permanently 

shadowed, and both radar data from Clementine and neutron spectrometer data from Lunar Prospector indicate that they contain deposits 

of water ice. 

6. Close-up mosaic of high-resolution images from the Clementine mission showing the illumination conditions near the south pole of the 

Moon. Because the spin axis of the Moon is perpendicular to the plane of the Moon’s orbit around the Sun, portions of the polar regions 

are in permanent darkness while others are in near-constant illumination. In this image, the colors indicate the fraction of the lunar day 

(708 hours) a given area is in sunlight. Note that a small region on the left rim crest of the crater Shackleton (at center) is illuminated for 

between 70% and 80% of the lunar day. This site has many advantages for the future habitation of the Moon.

7. Lunar sample 15455, an impact breccia collected by the Apollo 15 mission in 1971. This rock is a mixture of several rock types, created in a 

large impact, probably the one forming the Imbrium Basin on the Moon. The black portion consists of melt rock made by the large shock 

wave of the impact while the white portions are bits of ancient lunar crust picked up during the basin formation. This rock formed about 

3.85 billion years ago.

8. Lunar sample 15535, a mare basalt collected by the Apollo 15 mission in 1971. This rock is a piece of an ancient lava flow, erupted onto the 

lunar surface over 3.3 billion years ago. In this microscopic view, the brightly colored minerals are pyroxene, a magnesium-rich mineral, and 

the large, gray, lath-shaped crystal is the mineral plagioclase, rich in aluminum and calcium. The black grains are ilmenite, an iron-titanium 

oxide. Such samples indicate that the Moon has been volcanically active in the distant past.

9. Maps of the topography of the Moon, derived from both laser ranging and stereo photography of the poles from the Clementine mission. 

The nearside (left) and farside (right) maps are color-coded, with red being high elevation and purple being low. The nearside is relatively 

smooth, with a range of relief of only a few kilometers, but the farside shows the complete dynamic range of lunar topography, from –8 km 

on the floor of South Pole-Aitkin Basin to +8 km on the rim crest of that basin.

10. An imagined future on the Moon, showing some of the activities we might undertake there. The long, linear feature is a mass driver, a method 

of using magnetic levitation and propulsion to launch materials off the Moon’s surface without rockets. In this case, oxygen produced from 

lunar materials is shipped into space for use in orbital refueling stations. The array of dish antennas at right remind us that the surface of the 

Moon is an excellent place to observe the universe around us. Here, a radio telescope interferometer (an instrument used to integrate data 

from two or more telescopes) yields high-resolution maps of the radio sky. At bottom right, a young explorer shares the vista of the 

settlement on the New World with a parent. Artwork by Pat Rawlings.
MMOON OON F FACTS ACTS Mass 7.35 × 1022 kg (1% mass of Earth)

Radius 1738 km (27% radius of Earth)

Surface area 3.79 × 107 km2 (7% area of Earth)

Density 3340 kg/m3 (3.34 g/cm3 )

Gravity 1.62 m/s2 (0.17 gravity of Earth)

Escape velocity 2.38 km/s

Orbital velocity 1.68 km/s

Inclination of spin axis (to Sun) 1.6°

Inclination of orbital plane (to Sun) 5.9°

Distance from Earth closest: 356,410 km; farthest: 406,697 km

Orbital eccentricity 0.055

Albedo (fraction of light reflected) 0.07–0.24 (average terrae: 0.11–0.18; average maria: 0.07–0.10)

Rotation period (noon-to-noon; average) 29.53 Earth days (709 hours)

Revolution period (around Earth) 27.3 Earth days (656 hours)

Average surface temperature 107°C (day); –153°C (night)

Surface temperature in polar areas –30° to –50°C (in light); –230°C (in shadows)

Earth’s Moon

AADDITIONAL DDITIONAL R RESOURCES ESOURCES

Books and Articles

Cernan E. and Davis D. (1999) The Last Man on the Moon. St. Martin’s Press, New York.

Chaikin A. (1994) A Man on the Moon. Viking Press, New York. 670 pp.

Harland D. M. (1999) Exploring the Moon: The Apollo Expeditions. Springer, New York.

Heiken G. H., Vaniman D. T., and French B. M., eds. (1991) The Lunar Sourcebook: A User’s Guide to the Moon. Cambridge University 

Press, New York. 736 pp.

Light M. (1999) Full Moon. Alfred A. Knopf, New York.

Spudis P. D. (1996) The Once and Future Moon. Smithsonian Institution Press, Washington, DC.

Wilhelms D. E. (1993) To a Rocky Moon: A Geologist’s History of Lunar Exploration. University of Arizona Press, Tucson. 477 pp.

Web Sites

Contact Light; A Personal Retrospective of Project Apollo — http://www.retroweb.com/apollo.html

Exploring the Moon (LPI) — http://cass.jsc.nasa.gov/moon.html

Hawai’i Space Grant Consortium Moon Activities On-line — http://www.soest.hawaii.edu/SPACEGRANT/class_acts/

Lunar Bases and Space Activities of the 21st Century (Online Edition) — http://adsbit.harvard.edu/books/lbsa/

Lunar Explorers Digest Book List (JSC) — http://ilewg.jsc.nasa.gov/ILEWG/led.html

Lunar Sample Information (JSC) — http://www-curator.jsc.nasa.gov/curator/lunar/lunar.htm

NASA Educator Guide, Exploring the Moon — http://spacelink.nasa.gov/products/Exploring.the.Moon/

NASA Education Program — http://education.nasa.gov/

Office of Space Science (OSS) — http://spacescience.nasa.gov

Origin of the Moon (Online Edition) — http://adsbit.harvard.edu/books/ormo/

Romance to Reality: Moon & Mars Expedition & Settlement Plans — http://members.aol.com/dsfportree/explore.htm

The Apollo Lunar Surface Journal (NASA) — http://www.hq.nasa.gov/office/pao/History/alsj/

The Lunar Almanac (Reston) — http://www.reston.com/astro/lunar/almanac.html

Please take a moment to evaluate this product at http://ehb2.gsfc.nasa.gov/edcats/educational_wallsheet.

Your evaluation and suggestions are vital to continually improving NASA educational materials. Thank you.

Produced in 1999 by the Lunar and Planetary Institute. The Institute is operated by the Universities Space Research Association

under Contract No. NASW-4574 with the National Aeronautics and Space Administration. LPI Contribution No. 974.

NW-1999-10-154-HQ