The breathtaking lunar landscape displayed on the opposite page was one of Orbiter lI's grandest photographic achievements. [Compare it with one of the best pictures of the same scene that Earth can offer (right), made with the 61-inch telescope of the Lunar and Planetary Laboratory, University of Arizona. ]
"On first seeing this oblique view of the crater Copernicus," declared ORAN W. NICKS, Deputy Associate Administrator, Office of Space Science and Applications, NASA, "I was awed by the sudden realization that this prominent lunar feature I have often viewed by telescope is a landscape of real mountains and valleys, obviously fashioned by tremendous forces of nature. It is no wonder that some writers immediately classified it as the 'Picture of the Year'! [Some, with understandable enthusiasm, even hailed it as the 'Picture of the Century.']
"Lunar Orbiter II recorded this image at 7:05 p.m. e.s.t. on November 28, 1966, from 28.4 miles above the Moon's surface, and about 150 miles due south of Copernicus. The clarity of the view is attributable to the absence of atmosphere. A photograph from similar altitudes of distant features on Earth would never be as sharp, because of haze.
"Copernicus is about 60 miles across and 2 miles deep: 3000-foot cliffs, apparently landslide scarps, can be seen. Peaks near the center of the crater form a small mountain range, about 1500-2000 feet high and 10 miles long.
"The Lunar Orbiter photography was accomplished with two cameras," Nicks explained, "one having a 3-inch focal length and the other a 24-inch focal length. These cameras were boresighted, so that each high-resolution photo was always contained in a moderate-resolution frame. Lunar Orbiter cameras were relatively conventional film cameras that combined a Bimat chemical development process with an electronic scanning readout for transmission by radio to Earth. The film images provided a very effective method of storing information for transmission bit by bit, at a modest rate."
"The telescopic view of Copernicus shown above is one of the finest photographs ever taken of this region from the Earth, and shows features as small as 2500 feet across," said WILLIAM E. BRUNK, Planetary Astronomy Chief, Lunar and Planetary Programs Directorate, NASA. "It is not possible to photograph smaller features because of the turbulence in the Earth's atmosphere.
"The crater Copernicus, a prominent feature on the lunar landscape, is believed to have resulted from an impact of a second body with the Moon," Brunk continued. "The 'keyhole'-shaped crater,....
....Fauth, is seen at the bottom of the photograph; the Carpathian Mountains at the top. Characteristics of the landscape are clearly shown by the shadows produced by the rising Sun, whose elevation was approximately 10 degrees above the horizon. Numerous mounds are visible on the floor of Copernicus, in addition to the central peaks."
The reader will find it interesting at this point to compare the pictures shown here with Orbiter V's vertical views of Copernicus on pages 116-117.
Evidence of apparent volcanic activity in the Moon's past is seen in the top photo here. CLIFFORD H. NELSON, Lunar Orbiter Project Manager, Langley Research Center, NASA, described this view:
"This magnificent northerly oblique photo from Lunar Orbiter 11 brings to view the Marius Hills region shortly after lunar sunrise. The picture was taken on the last day of Lunar Orbiter 11 photography, November 25, 1966, with image-motion compensation turned off.
"The slow curvature of the horizon is 250 miles from Orbiter's wide-angle (40°) camera. The crater Marius, at 50.7° W, 12° N, is about 25 miles in diameter and I mile deep. its floor is surprisingly level.
"The central portion of this scene is dominated by a spectacular array of dome structures. These domes are up to 10 miles in diameter and as much as 1500 feet high. Many features are similar in appearance to volcanic domes in northern California and Oregon. They are interpreted to be the result of upward movement of magma that has warped the overlying rock and in some cases spilled out on the surface as lava.
"The irregular lines of hills that cross this lunar scene diagonally appear as wavelets washing across shallow beach areas on Earth. These hills have apparently been formed from lava flowing out through cracks in the Moon's crust."
Some of the largest rocks seen in early lunar missions are visible in the Orbiter 11 photograph on the opposite page.
"This rock-strewn area," explained FRED A. ZIHLMAN, Lunar and Planetary Programs, NASA, "is situated in the southeastern part of Mare Tranquillitatis. Some of the larger rocks are about 30 feet across. This photograph, covering an area 1200 by 1500 feet, is enlarged five times from the original filmstrips.
"The photograph is interesting because of the relatively large size of the rocks shown and because of the circular distribution of rocks in the center of the picture. Some lunar scientists suggest that the rocks were broken and excavated from subsurface layers by meteoric impacts, and that in this area which is part of a ridge, finer ejecta material has been gradually removed by some 'mass-wasting' process that uncovered the rocks in the process of filling the impact craters.
"Distributions of rocks were also photographed by Surveyors I and III in the region of Oceanus ProcelIarum. Surveyor I pictures show a fairly large number of blocks on the horizon, the coarser ones about 3 feet across. At the Surveyor III landing site. the coarsest blocks, scattered mainly in two distinct strewn fields, range in size from a few inches to approximately 6 feet across. The rocks shown above. considerably larger than those photographed by Surveyors I and III, may have been raised by larger meteoric impacts and from greater depths."
"We naturally began our selection of potential Apollo landing sites by examining Earth-based data," said ARTHUR T. STRICKLAND, Cartography Chief, Lunar and Planetary Programs, NASA, "and choosing generally smooth-looking lunar areas, ostensibly devoid of craters, as the most promising. The smooth area outlined by a black rectangle on a small portion of the best available topographic chart of the Moon [at left] is one area we originally picked. This site, approximately 20 miles long and 11 miles wide, is in the northeastern section of the central highlands, slightly south of the Rima Ariadaeus and west of Mare Tranquillitatis.
"Detailed photographic examination of this area by Lunar Orbiter lI's camera, as evidenced above on the preceding page, demonstrated to us how inadequate Earth-based instruments and methods are to define the lunar terrain for a Lunar Module's landing."
"When Lunar Orbiter II took that high-resolution photograph of the site," commented SAMUEL C. PHILLIPS, Apollo Program Director, "the terrain was revealed to be extremely rough and obviously unsuitable for an early manned landing attempt.
"We were delighted, however, to find many areas similar to the one marked with a white ellipse above, which are smoother and will no doubt yield acceptable sites for manned landings. The area above, shown in high-resolution photography obtained from Lunar Orbiter III, is one of the likeliest candidates from which the initial Apollo landing site will be selected. The ellipse [a shape dictated by the nature of the Lunar Module's landing approach] covers approximately 5 miles by 3 1/4 miles. It is located in southeast Oceanus Procellarum, at 3°30' S and 36°25'W. Its selection was based on considerations of topography, surface bearing strength, and flight operations. "
"In November 1966, Lunar Orbiter II took this high-resolution photograph of the area on the western edge of Mare Tranquillitatis where Ranger Vlll had impacted on February 20, 1965," explained NEWTON W. CUNNINGHAM, former Ranger Program Manager, NASA. Ranger Vlll had photographed parts of this area, and in this picture the mark it left on the Moon was found.
"Ranger Vlll had not been able to photograph its impact point because the optical axis of its cameras was not alined with the trajectory of the incoming spacecraft. However, framed regions representing the last areas photographed by Ranger Vlll's 'A. 'B,' and 'P' cameras were superimposed on the....
....Lunar Orbiter II picture, as has been done here. By plotting the resultant camera trace, it was then possible to determine Ranger VIIl's trajectory trace on the surface of the Moon.
"A 10-x enlargement [shown above] was next made of two framelets of Lunar Orbiter lI's photo [each covering 200 meters of surface].
"On this enlargement," Mr. Cunningham continued, "the extended plot of Ranger Vlll's trajectory crossed from lower left to upper right, passing near the two craters Cl and C2. On the basis of Ranger VlIl's mass of 800 pounds, its impact velocity of 2.655 km/sec, and the computed angle of approach from the local horizontal (41°), it was concluded that Cl could be the crater made by Ranger Vlll's impact. Additional support for this conclusion comes from the bright halo of new material thrown up from the surface and the generally elliptical shape of Cl, pointing along the direction of Ranger Vlll's Right."
" These photographs of Surveyor l's landing area in Oceanus Procellarum were taken by Lunar Orbiter III on February 22, 1967, from an altitude of 30 miles, explained WALTER JAKOBOWSKI, Surveyor Program engineer, NASA. "The left-hand panel is an oblique, wide-angle view showing a partial ring structure of low mountains, with the crater Flamsteed at the southern tip of the ring. By triangulating from those mountains, which were visible in Surveyor l's photographs, the landed spacecraft's approximate location was determined. It was then possible to find Surveyor I in the center picture, which is Orbiter IlI's high-resolution photograph of the area. The right-hand panel is a portion of the center picture enlarged by a factor of 8. The spacecraft, with its three bright landing-gear surfaces, appears as a triangular white spot in the center of the circle To the top and left of this spot is the 30-foot shadow cast by Surveyor's solar panel and antenna.
"The locating of Surveyor I in these pictures is significant in that Orbiter's vertical view permitted the scaling of distances and determination of the size of features seen in the Surveyor photographs, which otherwise would not have been possible. It also will permit extrapolation of Surveyor's detailed findings on local lunar-surface characteristics to other areas of the Moon that, according to Orbiter pictures, are similar in general characteristics to the area in which Surveyor I landed."
"Here," explained ISRAEL TABACK, Lunar Orbiter Project Office, Langley Research Center, NASA, "are a wide-angle [above, left] and a telephoto photograph of the far side of the Moon, taken simultaneously by Lunar Orbiter III on February 19, 1967. The spacecraft was in a position near the Equator and about 900 miles above the surface. It was commanded to look obliquely south. The area of the far side included in the wide-angle photo is the eastern part of the Southern Hemisphere and spans from about 10° S, at the top, to 55° S, at the bottom. The width of the area covered near the Equator is approximately 750 miles.
"The telephoto photograph shows the central region of the area covered by the wide-angle photograph, at a much better resolution Each strip [delineated by faint parallel lines] is about 4 3/4 miles wide.
"The area shown in the wide-angle frame is predominantly cratered, as is the entire far side. In this way it differs considerably from the front side, where numerous mare basins are present. There are some of these on the far side, and the crater with the very dark floor, seen near the center of the wide-angle photo, is a prime example [compare p. 45] This crater, partially covered by the telephoto frame [right] at a significantly better resolution, is about 150 miles in diameter. It has been named Tsiolkovsky . Its features seem indicative of the processes that occur during mare formation."
"The most impressive feature of the photograph above, declares LAWRENCE C. ROWAN, U.S. Geological Survey, "is the crater Kepler, 20 miles in diameter, near the center of it. The picture, taken by Lunar Orbiter III, shows an oblique view of the contact between the dark mare of Oceanus Procellarum in the south and the bright and rugged upland in the north.
"Kepler is generally believed to have been formed by meteorite impact. Chains of small craters alined....
....radially to it are superposed on both the mare and upland. They are most clearly defined in this photograph where they cross the mare south-southwest of Kepler. These chain craters appear as very bright rays on full-Moon photographs and were formed by impact of ejecta from Kepler. Superposition relations of this type show that the primary crater is younger than the subjacent material."
"The crater Hortensius [above]," says CHARLES J. DONLAN, then Associate Director, Langley Research Center, NASA, "is one of the smallest named craters, known chiefly for the domes north of it. This picture was taken by Lunar Orbiter IlI's 80-mm focal length camera on February 20, 1967, from an altitude of 33.3 miles. The scene is remarkable not only for the fine detail of previously perceived features but for the abundant and clearly defined northeast-southeast tectonic structures."
"This view [above] encapsules the major events of lunar geologic history in the central part of the visible side of the Moon," said DON E. WILHELMS, U.S. Geological Survey. "It is one of many Lunar Orbiter III obliques whose objective was greater coverage than obtainable by vertical photography.
"The view looks northeastward at crater Murchison [55 kilometers in diameter], with part of crater Pallas at center left edge and part of crater Ukert [23 kilometers] at top, to right of center. Murchison, Pallas, and other craters, partly in view in the foreground, formed early, in pre-lmbrian time. These craters were then strongly affected in two ways by the formation, probably by impact, of the Imbrium Basin [outside picture to northwest]. They were cut by fractures radial to the basin; for example, the incomplete southeast rim of Murchison [at right edge] appears to be downdropped along faults. Second, the craters were partly covered by ejecta from the basin. The ejecta, which forms the tolling terrain in the upper fourth of the picture, has swamped the north rim of Murchison and spilled into the interior. Later events, in the time period called Imbrian, included the formation of the crater Ukert and the flooding of its floors, now cracked in places, by mare material and other volcanics."
"The moderate-resolution photograph on this page, explained NORMAN L. CRABILL, of Langley Research Center, NASA, "was taken by Lunar Orbiter III on February 22, 1967, at an altitude of 35 miles, near the point 1° N, 58° W, in the southern part of Oceanus Procellarum, looking generally southwestward.
"This particular photograph was taken to determine whether the innermost crater, Damoiseau, of the large, double-walled crater at right center is a collapsed volcanic structure, as it appears to be from Earth-based telescopic observations. According to scientists of the U.S. Geological Survey, this oblique photo alone is not conclusive. However, a careful review of another Orbiter III photograph of the same area, a vertical view, indicates that the inner crater is indeed a collapsed volcanic crater and the outer wall the remnant of an older, impact crater.
"Another interesting aspect of this photograph is the contact between the marelike material in the foreground and the steep, semicircular cliff at its far edge. This headland has extremely steep sides, yet there is very little evidence of slumping at the base. This suggests that the mare material has flooded an old crater, its near rim already worn away by meteorite impact or submerged in general tilting."
"This oblique photograph [above] of the crater Theophilus was taken by Lunar Orbiter III on February 17, 1967," wrote E. C. DRALEY, Assistant Director for Flight Projects, Langley Research Center, NASA. "The spacecraft was looking south from a position near the Equator. The crater observed adjacent to Theophilus and almost at the horizon is Cyrillus.
"Theophilus is about 60 miles in diameter and approximately 4 miles deep. It has a very pronounced central peak, comparable in height to Mount Mitchell, the tallest mountain [6684 feet] on the east coast of the United States.
"This photograph will allow the visible characteristics of Theophilus to be compared with those of other large craters, such as Copernicus [pp. 116-117] and Tycho [pp. 120-121], that have been photographed by Lunar Orbiter spacecraft. This can now be done at a scale that was impossible prior to the Lunar Orbiter photography."
On the opposite page is a superb oblique photograph of the northern portion of Oceanus Procellarum. The Cavalerius Hills are in the foreground. The largest crater in the background is Galilei, about 10 miles across and over a mile deep. its rims are 1000 feet above the surrounding terrain.
"Lunar Orbiter 111 made this picture from an altitude of 38 miles," said WILLIAM J. BOYER, Langley Research Center, NASA. "It was then 160 miles south of Galilei, just north of the Equator, and 1300 miles west of the center of the front face. The spacecraft was alined so that north in the picture is just left of top center.
"Contained in this frame of photography is the landing site of Russia's Luna IX [p. 50], which softlanded there February 3, 1966, the first spacecraft to do so. The best estimate of its location is near the central portion of the picture.
"I particularly remember," Boyer concluded, "that when this photograph was received from Lunar Orbiter III at the Control Center, in Pasadena, several of us spent many minutes scanning the negatives for some telltale shadow or reflection of Luna IX, but we were forced reluctantly to conclude that it was beyond the picture's resolution capabilities."
"A boulder that rolled downhill and the track it made on the Moon are shown in the Lunar Orbiter photograph at left, wrote NEWELL J. TRASK, of the U.S. Geological Survey. "The track makes it evident that the surface material at this location [on the southeast interior wall of a mile-wide crater informally named 'Sabine EA,' at 2°48' N, 24°54' E] is soil-like, neither solid rock nor deep dust. North is at top, and the surface slopes gently from southeast to northwest. The track is 1200 feet long, 6 to 15 feet wide. its freshness suggests that the boulder rolled relatively recently, probably dislodged by a small moonquake caused by a high-velocity impact nearby."
The dramatic Lunar Orbiter III photograph above is of the Hyginus Rille. HAROLD MASURSKY, Chief, Branch of Astrogeologic Studies, U.S. Geological Survey, explains that this rille is "located in the central part of the Moon. it's about 130 miles long, 2 to 4 miles wide, and about 1200 feet deep. It is a fault trough, or graben, with volcanic craters well developed along the western branch of the valley. The volcanic nature of the craters is indicated by the buildup of material around the vents: that is, the lips of the craters could not he made by collapse of material into the craters
"The graben cuts rolling highland-basin fill material and mare material near the crater Hyginus, 8 miles in diameter, located at the bend in the valley. Exposed here are mare materials, upland-basin filling material, and the volcanic rocks near the craters. These vents may give suitable samples to study the composition of the Moon at great depths."
Informative fine details of the Moon's surface not discernible from Earth are revealed in the Lunar Orbiter III photos explained on these pages.
"A fresh crater 500 feet in diameter is seen near the center of the high-resolution photograph [right] of the cratered mare surface of Oceanus Procellarum, wrote WILLIAM L. QUAIDE and VERNE R. OBERBECK, Ames Research Center, NASA. "It has a double-walled, concentric geometry peculiar to a size class of lunar-impact craters. Laboratory studies have shown that craters with this geometry are produced by impacts of projectiles against layered targets consisting of a loose surface layer Iying on stronger subsurface rock. The outer part of the crater was formed in loose surface materials and the inner part in the subsurface rocks.
"Blocks of rocks ejected at low velocities from the central crater can be seen in the rays symmetrically disposed about the crater. Some of the ejected blocks have produced secondary craters upon impact against the loose surface materials. Many of the secondary craters have teardrop shapes. Some have sinuous furrows extending from the secondary crater in a direction generally outward from the parent concentric crater, terminating against the blocky secondary projectiles. The presence of these furrows further attests to the loose state of aggregation of the surface materials.
"The smaller, subdued-looking crater, 300 feet in diameter, below and to the right of the central one, has been severely eroded, but still retains evidence of its original concentric morphology. At an earlier time it may have had the same appearance as that of the fresh concentric crater.
"In fact," the commentators added, "craters of various geometric shapes and all degrees of freshness can be seen in this photograph, indicating that erosional processes must have continually modified the appearance of the lunar surface. This modification has been accompanied by repetitive bombardment of meteorites and cometary particles of all sizes.
Such repetitive impact has not just modified the appearance of the lunar surface, but, by crushing and grinding the originally hard surface rocks, it has produced the layer of loose material found there.
"Considerations of the size distribution of craters with morphology such as this has made it possible to measure the thickness of the surface layer at many places on the Moon, and thus determine the relative ages of formation of the hard rocks now covered by the loose mantle of debris."
"Characteristic features, heretofore not visible from Earth, of the floor of the northeastern part of crater Hevelius, near the far-west limb of the Moon, are impressively displayed in the photograph at top left, opposite page, points out VERL. R. WILMARTH, Lunar and Planetary Programs, NASA.
"Hevelius is an old crater, about 60 miles in diameter, and similar to other large old craters. Many smaller, still younger craters are common in its floor and walls. The young craters-like the one, about 2 miles across, shown near the center of this photograph-are predominantly round, though a few are elongate. They have raised rims, but well-defined...
...throwout rays are not present. These features indicate that an extensive layer of weakly cohesive materials fills the crater and covers the crater walls.
"The most striking feature of this photograph," Wilmarth declares, "is the intersecting system of northwest- and northeast-trending rilles, trenches as wide as 3500 feet and several tens of feet deep. Two distinct ages of rilles are present. The oldest rille, not far from the left edge of the photograph and nearly parallel to it, is characterized by subdued walls. The other rilles are younger, have sharp walls, and are less modified by later surface processes.
"Rilles are interpreted as surface expressions of subsurface structural features of dynamic origin. This thesis suggests that two periods of diastrophism have Occurred since Hevelius was formed. Similar structural features known on Earth are in some instances formed by upwarping of the surface rocks, by compaction, or by withdrawal of subsurface material."
"Part of an old lunar hill, one of several enclosing the basin of the ancient crater Flamsteed P., filled with mare material, is shown in the high-resolution photo at top right, wrote MARTIN J. SWETNICK, Lunar Orbiter Program scientist, NASA. "The hill, located at 42.8° W, 2.4° S, is the dominant feature in the picture, taken at a height of 32 miles, when the Sun was to the right at an elevation of 19° above the local horizon. Although the area covered is 3.3 by 2.7 miles, surface features as small as 4 feet in diameter can be readily resolved. North is toward the upper-left corner of the photograph.
"The crest of the hill is 1000 feet above the cratered door of the basin," Swetnick continued. "The western, or shadowed, side of the hill has a slope of about 18°. The slope of the eastern side is less than 10°. The features of the western slope have scientific significance in that they provide evidence for the occurrence of mass wasting. A terrace, or talus slope. consisting of fragmented material can readily be seen along the base of the western slope. The terrace was most likely formed by a landslide down that slope. Ledge rock exposed by this landslide can be seen near the crest of the hill. The texture of the terrace material is distinctly finer than that of the material higher on the hill slope. The density of craters on the terrace is much less than on the basin's floor."
"The prime objective of Lunar Orbiter IV," wrote JAMES S. MARTIN, Deputy Lunar Orbiter Project Manager, Langley Research Center, NASA, "was to photograph the entire front side of the Moon at a resolution considerably better than is possible from Earth. The mosaic on the opposite page is the result. The pictures, taken May 11-25, 1967, span an area from the North Pole (at top) to the South Pole, and from the eastern limb (at right) to the western limb.
"The complete mosaic is approximately 40 by 45 feet. It was laid on the floor, and observers were allowed to stand on it or crawl over it in their stocking feet. Some astronomers chose the latter course, carrying magnifying glasses. The mosaic was a primary source in selecting scientific sites for Lunar Orbiter V to photograph at higher resolutions."
"The first swath of Lunar Orbiter IV's nearly polar orbit of the Moon on its mapping mission disclosed some hitherto unseen areas beyond the eastern limb," commented LEON KOSOFSKY, Lunar and Planetary Programs, NASA. "One of the most striking features disclosed was the large trough visible in both photographs above.
"This great gash [at top left of the biggest crater in the wide-angle photograph; enlarged at upper right] is about 150 miles long and averages 5 miles in width. It is the most prominent of 3 valleys radiating from that large, double-rimmed crater. Presumably the valleys were formed by the impact that created the crater. There are radial valleys near other very large craters. As the enlargement shows, the edges of this trough are raised and scalloped, giving it the appearance of a chain of closely spaced craters.'
"Lunar Orbiter IV was about 1700 miles above the Moon on May 25, 1967, when its wide-angle and telephoto cameras simultaneously took the two dramatic photographs paired on these pages," said A. THOMAS YOUNG, Lunar Orbiter Project Office, Langley Research Center, NASA. "The wide-angle photograph [above] shows the large, circular Orientale Basin, appearing as a gigantic ball's-eye on the western limb of the Moon. The Cordillera Mountains, rising some 20 000 feet above the adjacent surface, form the outer ring, which is approximately 600 miles in diameter. The State of New York would easily fit within it.
"The telephoto view on the opposite page magnifies in remarkable detail the portion of the wide-angle photograph showing the area just to the right of center of the Orientale Basin.
"Large, circular basins such as Imbrium, Crisium, and Orientale are major features on the Moon, and therefore of great importance to lunar science. The...
...sharpness of the features portrayed in these photographs has led many lunar scientists to interpret Orientale to be one of the youngest of the large basins. Orientale's appearance is considered to be typical of how the older basins, such as Imbrium, looked earlier in their long history."
The Orientale Basin is centered at 89° W, 15° S, on the extreme western edge of the Moon's visible side. It is interpreted as having been formed by the impact of a giant meteorite or comet nucleus, and as being only partly filled by the younger, dark volcanic material.
Its outer rim is covered by ejecta hurled from the basin. Within Orientale's outer ring, the Rook Mountains, seen in the upper-right portion of the telephoto view, form another circular scarp, about 400 miles in diameter. At the center of the Orientale Basin is the dark Mare Orientale, which is about 186 miles in diameter.
"The crater Riccioli, occupying the right center of the high-resolution Lunar Orbiter IV photograph on the opposite page, is about 130 kilometers in diameter and lies about 750 kilometers to the northeast of the center of the Orientale Basin," explained J. F. MCCAULEY, of the U.S. Geological Survey.
"Pre-Orbiter telescopic work by Hartman and Kuiper, of the Lunar and Planetary Laboratory, University of Arizona, and by me suggested that Orientale was the youngest of the large lunar basins. Orbiter IV convincingly proved this hypothesis.
"The well-preserved, grooved-to braided texture of the 'blanket' that surrounds Orientale can be seen in the accompanying photograph. The fact that it mantles pre-Orientale craters, such as Riccioli, is also evident. The blanket is clearly draped over the crater wall nearest Orientale, but is banked up into crude dunes on the far wall [upper-right side of Riccioli]. The material of the blanket apparently 'Rowed' over the rim nearest Orientale and out over the crater floor, but, upon reaching the far wall, lacked sufficient energy to move in an upslope direction.
"Similar 'dunelike' deposits are found at the base of topographic obstacles at comparable distances from Orientale around the entire basin. Near the Cordillera Mountains, closer to the center of Orientale, preblanket craters are completely mantled, and the 'banking-up' effect cannot be seen. These features are interpreted to be the product of surface flow in a base-surge cloud of the type known to occur in nuclear and high-explosive cratering events.
"The new data contained in the Orbiter IV photographs of the Orientale Basin," McCauley concluded, "strengthen the hypothesis of an impact origin for large lunar basins."
"This photograph of the Earth [opposite page] was made by Orbiter V as it circled the Moon in a polar orbit 214 860 miles away," commented LEE R. SCHERER, Lunar Orbiter Program Manager, NASA. "It does not quite include the full sunlit surface. The picture is centered over India, while the Sun was directly over Saudi Arabia.
"The clear outline of the entire east coast of Africa and the Cape of Good Hope can be seen. Prominent geographical features such as Italy, Greece, Turkey, the Black Sea, the Suez Canal area, the Red Sea, and the Persian Gulf are discernible.
"This was one of the secondary photographs of Orbiter V's mission, but it attracted high public interest around the world for a variety of reasons.
It was the first picture of the nearly full Earth as seen from the Moon distance.
"Wags examining this photograph have stated that life obviously could not exist on such a shrouded planet. To most, this was humorous, but thoughtful scientists noted the distinct resemblance to photographs of Venus, and interest in the exploration of that planet was heightened.
"To the philosopher, this picture is close to man's soul, since it allows him to look back upon his own world, and thus fosters the feeling of man's emancipation from the bounds of Earth Perhaps to most of us the interest is due to human vanity, which dictates that self-portraits are always the best portraits "
"The medium-resolution [above] and high-resolution photographs of the crater Copernicus shown here, said TERRY W. OFFIELD, of the U.S. Geological Survey, "were taken by Lunar Orbiter V from an altitude of 63 miles above the Moon's surface in August 1967." The area within the rectangle, shown enlarged on the opposite page, is 12 1/2 miles wide and 17 1/2 miles long.
"Copernicus [see also pp. 88-89] is relatively young and fresh. The medium-resolution photo....
....graph shows a hummocky crater rim, numerous large slump blocks on the crater wall, and a complex of central peaks. Sets of parallel fractures, alined with the Iunar structure grid, formed after the crater wall took its present form, but before the smoothest floor materials were emplaced. The smooth floor materials show a swirling pattern of cracks like those seen on terrestrial lava flows. These materials are associated with numerous hills that have summit craters and are probably small volcanoes. Several low places on the rim and wall are partly filled by what appears to be ponded volcanic material, or possibly fluidized impact debris.
"The high-resolution photo," Offield concluded, "shows that flows apparently spilled through breaks in the pond walls and coursed down valleys to the crater floor, where they spread out as deltas or lobes. Ridges on the flows are natural levees, formed as material solidified faster along the channel sides than it did in the center."
"The tracks of numerous rolling boulders, some of them more than 100 feet across, are visible in Lunar Orbiter V's high-resolution photograph of the crater Vitello, on the southern edge of the Moon's Sea of Moisture, remarked KENNETH L. WADLIN, of the Lunar and Planetary Programs, NASA. "The picture was taken on August 17, 1967, from an altitude of about 100 miles.
"Two such tracks can be seen in the enlargement at right. The complex pattern of the 900-foot track left by the large boulder indicates that this boulder, which is about 75 feet across, is quite angular. The buffeting that it experienced in rolling did not cause it to break up or become rounded. This points both to the integrity of the material of which it is composed and to the deformable nature of the surrounding surface material.
"The more uniform track of a smaller, more rounded boulder can be seen to the right of the large one. This smaller boulder is over 15 feet across, and traveled 1200 feet before it came to rest.
"The boulders may have been set rolling by moonquakes or meteor impacts."
Orbiter V took more revealing photographs of the Hyginus Rille [top of opposite page-p119] than Orbiter III did [see p. 104].
"The moderate-resolution photograph at top left shows clearly the two elements of the rille system," explained HAROLD MASUKSKY, Chief, Branch of Astrogeologic Studies, U.S. Geological Survey. "First is the trough bounded by marginal faults. The graben, or downdropped block, is nearly a thousand feet below the surrounding plain. Disposed along the west branch of the fault valley are a series of volcanic vents, like beads on a string. The largest vent, the crater Hyginus, located at the bend in the valley, is 5 miles in diameter.
"Details of the fault valley and volcanic vent are more clearly visible in the high-resolution photograph at top right. In particular, abundant outcrops and boulders occur on the lip and sides of the vent. These blocks are the critical feature for, in terrestrial volcanic vents that greatly resemble these lunar ones, blocks occur that are brought up from great depths. In the Colorado Plateau area of the United States, blocks around such vents as these have been brought up from depths of 20 miles.
"It should be possible to make a manned landing in the relatively smooth topography adjacent to this valley'" Masursky concludes. "From this landing site, it should be possible to collect samples of typical upland materials from the walls of the trough, as well as samples from the vent that are brought up from deep within the Moon."
Below are moderate- and high-resolution photos by Lunar Orbiter V of sinuous rilles in the Marius Hills. ROBERT P. BRYSON, Lunar and Planetary Programs, NASA, gave this description: ". . . they are long, uniformly narrow rifts or valleys that, like river channels, pass across or through a 'wrinkle ridge' and between domes, or low hills. Unlike river channels, however, they appear to head in a basin or crater and decrease gradually in width and depth and disappear. Very likely they were formed by some type of freely Rowing material-possibly water [as Dr. Harold C. Urey has suggested], although, under the existing condition of low gravity and atmospheric pressure, as well as broad temperature extremes, water could have remained at the surface for no more than very brief periods."
"The youngest large impact crater on the Moon is Tycho, which is 53 miles in diameter and nearly 3 miles deep," commented HOWARD A. POHN, of the U.S. Geological Survey. Surveyor Vll [see p. 78] landed about 18 miles beyond its north rim, as shown in the medium-resolution view of Tycho above, taken by Lunar Orbiter V. [The white circle marks its landing area. The area within the rectangle, enlarged on the opposite page, is 27 by 35 miles.]
"This photograph shows the entire crater, including ejected crater materials, which form pronounced radial ridges and grooves. These ejected materials....
....are gradational from large, hummocky, angular blocks, nearest the crest of the crater rim, to fine, subdued materials, near the top of the photograph.
"The crater interior is characterized by a pronounced central peak, extremely hummocky floor, and steep, angular blocks in the walls. Many depressions along the eastern margin of the crater interior exhibit ponds of smooth materials that are thought to be the result of postcrater volcanism.
"The high-resolution photograph above shows the intricate structures that appear inside the crater, with the most interesting feature being the crater floor. The subparallel ridges and grooves, as well as the many cratered prominences, are reminiscent of the Bonita Lava Flow, in northern Arizona.
"The floor of Tycho is demonstrably younger than the crater rim, and was probably formed much later in lunar history, as a result of tapping deep-seated volcanic sources by fracturing that was associated with the Tycho impact."
"The youthful impact crater Aristarchus, viewed above in medium-resolution and on the opposite page in high-resolution photography by Lunar Orbiter V, is 23 miles in diameter and 10 000 feet deep," wrote DONALD U. WISE, associate professor of geology, Franklin and Marshall College. "It illustrates the interplay of geologic processes that complicate lunar land forms. Three major topographic zones are characterized by differing age and dominant geologic process. [The area within the rectangle, enlarged on the opposite page, is 11 by 14 miles.]
"Oldest of the zones is the debris apron, spreading outward for a crater diameter beyond the upturned rim. The second zone, a ring of slumped blocks, resulted from gravity collapse of the initial steep walls of the crater to produce the present, relatively stable 40 percent slopes. Many of these collapses utilized a preexisting northeast- and northwest-trending regional fracture system to produce an intersecting array of elongate slump blocks and an eyelike northsouth elongation of the crater [visible above].
"The third and youngest zone, strikingly similar in appearance to floors of Hawaiian volcanoes, is relatively Rat, strongly crevassed, and marked by many dome-shaped hills, 50 to 100 feet high. Absence of major disruption of the Rat floor by slump movement indicates that volcanic filling of the floor is younger than most of the wall collapse. Many late-stage modifications of the slumped-wall zone may have been coincident in time with the volcanic activity. Periodic sightings of red glows in the Aristarchus region suggest that this phase of crater modification may still be in progress."
"A lunar valley named after the renowned German selenographer Johann Hieronymus Schroter (1745-1816) is depicted in the excellent photographs above, said DENNIS B. JAMES, of Bellcomm, Inc. "The medium-resolution [left] and high-resolution photographs of it were taken simultaneously by Lunar Orbiter V on August 18, 1967, from an altitude of about 140 kilometers. The distance between vertical lines in the medium-resolution photograph above is 4300 meters.
"Schroter's Valley terminates in what lunar scientists have been inspired to call (for obvious reasons) the Cobra Head [bottom right in the photo], which is interpreted as its source. The valley's walls rise more than 1300 meters above its floor. It is near the craters Herodotus and Aristarchus, but closer to the former.
"In the cropped telephoto view at right above, the salient feature displayed is the meandering rille within Schroter's Valley," James continued. "The rille also emerges from the Cobra Head. As it meanders, more so than the valley itself, the rille moves from one side of the valley to the other, at one point forming a cutoff channel. These characteristics resemble those of meandering canyons, valleys, and streams on Earth. Of special interest also are the blocks of rock that separate from the valley's walls and leave behind them tracks of their downslope movement.
"Scientists believe that the valley and its meandering rille were formed by erosion of small particles carried by a Row of either a liquid or a gas.
"The distance between vertical lines in the high-resolution photo is 540 meters."
"Sinuous rilles are among the most unusual features of the lunar surface," declared MARTIN W. MOLLOY, program scientist, Apollo Lunar Exploration Office, NASA. "Perhaps billowing clouds from the fluid that carved meandering channels like those in the Harbinger Mountains, shown in the Lunar Orbiter V medium- and high-resolution photos at...
....the top of this page, boiled off in the ultra-high vacuum of the Moon and distributed fine particles uniformly over adjacent areas.
"The sinuous rilles along the right edge of the left-hand photograph show evidence of subsequent channel filling by mare material. The rille in the top center of the picture has cut through an older line of hills in Oceanus Procellarum. The large crater at the bottom is Prinz. Its floor is spattered by secondary ejecta from Aristarchus, just out of sight at lower left. Its rim is partly submerged in the material that has flooded Oceanus Procellarum.
"Flowing downhill [toward the top of the photo] from the rim of Prinz and out onto the mare surface is a rille with a narrow, new channel incised in the side of an older, broader channel.
"This same rille is seen in detail in the high-resolution photograph at right," Molloy added. "A small, recent crater located within the head of the older rille is the source of the new channel. The crater is so fresh that large blocks can be seen in its walls."
Though Surveyor l's television camera produced black-and-white images, one way existed by which it could transmit color. This was to shoot three separate pictures of the same scene through different colored filters, send them to Earth, and there reconstitute the picture through similar filters. One result of this complicated process was the photo above, which indicates that the lunar surface appears to be almost colorless.
In explanation of the picture, CLARK GOODMAN, of the University of Houston, said: "Since solar light is essentially white-composed of equal amounts of all wavelengths over the spectral range of the photographic film-the light reflected from the Moon is solar light minus any wavelengths specifically absorbed by the lunar grains. The fact that the reflected light is nearly colorless (nearly white) means that the lunar skin does not selectively absorb any particular wavelengths.
"Hence," said Goodman, "we conclude that the lunar material is not composed of a particular single colored mineral but instead is either a mixture of many different colored minerals or is a mixture of colorless minerals."
Another color reconstitution, on the opposite page, is a closeup of Surveyor IlI's footpad 2.
Remarking on it, J. J. RENNILSON, of the Jet Propulsion Laboratory, said: "Visible items of importance, from upper left to lower right, are: a small....
...portion of lunar soil, placed on the footpad by the surface-sampling instrument the attitude-control jet, with its gold-tipped nozzle contrasting with the gray of the lunar soil; and, lastly, a photometric target, consisting of several shades of gray as well as three colors.
"One of the major scientific achievements of the color analysis of such pictures as this one was the discovery that very little color differences were detectable between the immediate surroundings of Surveyor l's landing site and those of Surveyor IlI's landing site. The color of the disturbed soil remained the same as the color of the undisturbed surface."
"The color-reconstituted photograph at top right," said J. J. RENNILSON, of the Jet Propulsion Laboratory, "is the first one in which man has been able to observe an eclipse of the Sun by his own planet. Surveyor III took the view from the Moon with the wide-angle mode of its TV camera.
"Most prominent in the picture is the white cap of light caused by the bending of the Sun's light as it passed through the Earth's atmosphere. The cap is much brighter than the rest because of the Sun's proximity to that limb, causing a greater proportion of sunlight to be refracted. The beaded appearance around the remaining portion of the Earth's atmosphere is due largely to the interruption of the band of light by overcast areas. A small portion at the right of the solar-eclipse photograph was obscured by an edge of the camera's mirror.
"Blue light from the Sun is scattered out of the beam during passage through the Earth's atmosphere, leaving mostly the green, yellow, and red portions of the spectrum. A careful study of this and other lunar photographs of the solar eclipse will enable scientists to understand better the optical properties of our atmosphere."
"The historic color photograph of the crescent Earth [right], commented ROBERT F. GARBARINI, former Deputy Associate Administrator (Engineering), Office of Space Science and Applications, "was taken from the Moon's surface by Surveyor III on April 30, 1967. Only because of the tilt of the spacecraft and the favorable libration of the Moon was it possible to catch the Earth in the camera's wide-angle field of view."
On a later Surveyor mission, it was possible to command the camera to take narrow-angle photographs of the Earth having much higher resolution.
The photographs on the four following pages were taken by a television camera that was nearly 150 million miles away, farther from Earth than any camera had ever traveled before. It was riding on Mariner IV, which, after an interplanetary journey of 7 1/2 months, flew within 9847 kilometers of Mars on July 15, 1965.
The course of the spacecraft camera's picture coverage of Mars and the locations of the pictures on pages 130-133 are shown on this map.
Mariner IV's camera, its shutter automatically operating every 48 seconds as red and green filters were alternated before its lens, took a total of 21 complete pictures and a fraction of another.
These pictures provided man with his first chance since the invention of the telescope to view the surface of Mars without the hindrance of "straining to see through the Earth's atmosphere like a driver peering through a rain-spattered windshield," as Dr. Robert Jastrow has expressed it.
"At 00:18:33.1 GMT on July 15," said DAN SCHNEIDERMAN, Mariner 1967 Project Manager, Jet Propulsion Laboratory, "the first closeup black-and white photograph of Mars [above] was taken from the spacecraft through a red filter. The image center is approximately at 33° N, 171.6° E, and about 17 000 kilometers from Mariner IV. The spacecraft velocity relative to Mars was 4.913 km/sec.
"Surface features are not readily distinguished because of what appears to be a haze or cloud layer, which is enhanced by the oblique view. There is an uncertainty as to the condition of the lens at this time, and some glare may be present. The upper right-hand region corresponds with the area known as Phlegra. Because of the cloud layer, it cannot be determined whether the light and dark areas are due to changes in aspect of the surface, a series of breaks in the clouds, or a combination of these effects.
"The historic value of this photo is clear. Its scientific value lies primarily in its indication of the existence of clouds and its demonstration of the importance and feasibility of imagery as a scientific tool for planetary exploration."
"As conventional photographs were reconstructed from the coded radio signals sent back by Mariner IV, wrote BRUCE C. MURRAY, of the California Institute of Technology, "frame No. 9, shown above, was the first picture available to the TV Experiment Team that clearly showed a cratered, lunarlike surface, even including a characteristic central peak and some evidences of polygonalization of the craters.
[It took more than 8 hours for the spacecraft to send across some 140 million miles the 240 000 bits that constituted each photograph.]
"Many scientists before that time had considered the surface of Mars to resemble more closely that of the Earth than that of the Moon," Murray continued. "Picture No. 9, portending a complete rearrangement of Mars on the family tree of the solar system, must be regarded as one of the high points of discovery of the space age, if not of the 20th century. Because of the speed with which photographic data can be disseminated, and the universal understanding of pictures, the entire world truly shared in the excitement of this discovery."
"Among the several Mariner IV photographs that revealed Martian craters, perhaps the most spectacular was No. 11, shown above," commented ROBERT B. LEIGHTON, of the California Institute of Technology. "It contains more than 20 craters, including the largest well-defined one seen, as well as some of the smallest.
"In all, more than 100 craters, ranging in diameter from less than 5 to more than 100 kilometers, were seen for the first time. The craters appear to be of widely varying age, judging by their relative states. Their depths seem to be about 200 of preservation. to 250 meters.
"The above photograph also reveals, under closest examination, a long, straight, narrow structure 5 to 10 kilometers wide, running from lower right to the middle of the top. The narrowness and faintness of this particular lineation makes it unlikely that it would be recognized from Earth, but, together with the clear tendency for many Martian craters to have a polygonal shape, it gives evidence of the prevalence of linear fractures on Mars, as on the Moon."
"The noteworthy aspect of this Mariner IV photograph [frame No. 14] of the Martian surface," declared ROBERT P. SHARP, of the California institute of Technology, "is not that it shows more, larger, or better craters, but that several craters are outlined in white. This has been interpreted as a crusting of frost. Irregular white spots in the north-central part of the photo may be frosted areas in an irregular highland.
"The location is 41° S latitude within the light area Phaethontis. The area shown is above 140 by 170 miles. The time is late afternoon in midwinter, with the Sun to the north and 30° above the horizon.
"During winter at this latitude, frost could form each night over much of the landscape and might survive through the clay in favorably shadowed and properly located situations. The edge of the south polar cap is only 10° farther south at this season. More speculative is the nature of the frost. The most acceptable current model of the Martian atmosphere suggests that it may be solid CO2 rather than water frost."