P. M. MERIFIELD* (editor) J. M. SAARI R. 'vV. SHORTIlILL R. L. WlLDEY D. E. 'vVILHELl\'lS R. S. \VILLIAMS, JR.
Interpretation of Extraterrestrial
o - ) I I I ! Imagery KILOMETERS
FRONTISPIECE. The multiringed basin of Mare Orientale. Lunar Orbiter IV moderate resolution photograph. Framelet width is about 90 km. Framelet orientation varies among the various Orbiter missions. (See page 489.) Note: Jorth is at the top in this and succeeding lunar photographs. (NASA photo.)
Earth based telescopes; Photogeologic mapping of the Moon; Thermal mapping of the Moon; Lunar and planetary probes; Geologic interpretation of Lunar Orbiter photos; Photographic sensors for detecting extraterrestrial life.
(A bslract on next page)
TNTROD C'1'I0N * Chairman, Subcommittee V II, Photo Jnter HREE YEA RS HA VE elapsed si nce progress pretation Committee, American Society of Photo in the field of space imagery has been re grammetry, 1964-1967. Present address: Earth T Science Research Corp., Santa iVlonica, Calif. ported on to the members of the society (Van 90405. The authors are identified in their respective Lopik, Merifield, et at, 196.1), and a review of sections. 477 478 PHOTOGRAMMETRIC ENGINEERING some of the major projects that have been Ii te imagery of the earth is the subj ect of a undertaken is deemed appropriate. Terrestri subsequent paper to be published in this jour ally based telescopic photography and in nal. Al though this paper is intended to encolll frared imagery are continuing to be utilized as pass the broad spectrum of the subject, it can fundamental tools in the study of celsetial not be considered comprehensi\·e. Many proj bodies. Knowledge of the lunar and Martian ects ha\·e been reported elsewhere, and in such surfaces has been increased many fold by instances, the reader is referred to the ap imagery returned from Ranger, Surveyor, propriate literature. Lunar Orbiter and Mariner spacecraft. Satel-
ABSTRACT: Imagery interpretation is playing an important role in the investi gation of celestial bodies. Astronomers utilize terrestrially based photography in the identification and mensuration of celestial objects such as galaxies, plane tary nebulae, supernova remnants and sun spots. Telescopic photographs of the Moon are being used to construct 1: 1,OOO,OOO-scale maps of the lunar surface, and Earth-based infrared images of the Moon provide information on the dis tribution of hot spots and aid in tlte analysis of thermal contour maps. Snrveyor photography has yielded data 011 the size, shape and distribution of lunar sur facefragments as well as the mechanical and photometric properties of lunar soil. Illterpretation of Lunar Orbiter photographs cOlltinnes to provide '/lew illsight into the origi'/l and history of lunar snrface feat ures.
TERRESTRIALLY BASED TELESCOPES
PHOTOGRAPHIC IMAGERY Dl CLASSICAL ASTRO:-,rOMY*
T HE CAMERA THAT provides the astronomer design culminated in the last century in the with imagery is simply a large telescope in construction of the Yerkes 40-inch and Lick whose focal plane is placed a photographic 36-inch objective lenses, are usually most plate. The prj mary use categories of the de aberrant in chromatism and sphericity, while veloped plate are: (1) recognition and classi at sufficient distance from the optical axis fication of particular forms in the image de astigmatism becomes important. Modern, tail, (2) image photometry, and, the most large, fast reflecting telescopes have para time-honored of all, (3) the determination of boloidal surfaces so that perfect imaging is accurate relative positions of objects on the theoretically possible until such distance from celestial sphere. The observational difficulties the optical axis is achieved as allows coma to which confron t these endeavors are dom quickly set in. Except for telescopes designed inated by the principal problems of (1) specifically for wide-angle imagery, much use resolution and (2) radiative signal-to-noise is made of the naturally OCCUlTing coma-free ratio. The nearer objects are sufficien tly field. 'v\Then the 200-inch Hale telescope was bright that these two difficulties may be built, at f/3.3, the coma-free field was too considered independently, but fainter objects, small for adequately precise iris-diaphragm such as the outer regions of galaxies, presen t a photometry of stellar images, and a corrector situation in which the desired goals compete lens was designed by Ross to enlarge this fIeld with one another in a direct trade-off, because (Bowen, 1960a). the faster emulsion of a given type is always The epi tome of wide-angle telescopes is the the grainier one. true Schmidt camera, which makes use of the Most of the well-known astronomical fact that a spherical mirror has no optical axis telescopes are sufficiently large that off-axis and cannot, therefore, if a concentrically aberrations are of limited concern for the curved focal surface is used for the photo practical sizes of photographic plates. The sensitive surface, show coma or astigmatism classical large refracting telescopes whose (those aberrations which depend on size of field). Only spherical aberration is left, and * Contributed by Robert L. "Vildey, U. S. Geo this can be removed by figuring a corrector logical Survey, Flagstaff, Arizona. Publication plate, as an entrance pupil, as a figure of authorized by the Director, U. S. Geological Sur vey. revolution based on a calculated fourth- INTERPRETATION OF EXTRATERRESTRIAL IMAGERY 479 degree polynomial (Bowen, 1960b). Of course, afford the increased observing time required the reA ector plate does have an axis, bu t to reach the minimum detectable brightness because it is not a focusing de"ice its effects (Sandage and I'd iller, 1966). A typical emul are quite weak. sion used in o!Jsen'iug faint sources such as The angular resolution achievable in faint stars, distant galaxies, and gaseous astronomy is usually limited by the turbu nebulae would be an Eastman '
PHOTOGEOLOGIC MAPPING OF THE MOON* SYSTE~IATlC GEOLOGIC mapping of the Moon and crustal processes. The basic gross units from telescopic data has been carried out are (1) the dark, relatively smooth flat mare since 1960 by the U. S. Geological Survey. plains, and (2) the lighter rugged cratered Considerable geologic information about the terra (also referred to as uplands or high- Moon has been accumulated, and the way lands). Almost any hypothesis of formation prepared for unmanned Surveyor and Lunar of these gross provinces and of craters leads Orbiter spacecraft missions. The purpose of to the conclusion that the maria are younger lunar geologic mapping is to determine and than the terrae; the maria filled depressions map the stratigraphy and structure of the in the terrae as coffee fills a cup and have had Moon's crust, to work out from this the se- less time to become cratered than the terrae. quence of events that led to the present con- An extensive history has been worked out di tion of the surface, and to discover the by application of such reasoning in the processes by which these events took place. Archimedes area (Figure 1) between the Fifteen colored maps of the Moon's near side Apennine Ifountains (Montes Apenninus) at a scale of 1: 1,000,000 have been published and the main part of Mare Imbrium (Shoe- and an additional 31 are in preparation. maker, 1964). The oldest material forms the Geologic investigations of both the Earth rugged mountains themselves, which are part and Moon are carried out by dividing the of a circular ring of mountains around a crust, which at first appears to be bewild- circular depression, the 1are Imbrium basin. eringly complex, into units. These units are Second in age is the light plains material that rock bodies that seem to have a relatively fills in around the rugged material, and third uniform character over a wide lateral range the crater Archimedes, whose rim material and were probably laid down or emplaced in a and secondary craters are deposited on the relatively short period of time. Systematic light plains. Next youngest is mare material, geologic study of the Moon began when it was younger than Archimedes because a) the realized that rock units could be recognized mare fills Archimedes, and b) the extensive on the Moon and placed in an age sequence fan of Archimedes rim material and secondary through the interpretation of photographs. craters present on the light plains are missing Recognition of age units is perhaps the most on the mare. Youngest are the craters Auto noteworthy contribution of the geologist to Iycus and Aristillus, whose crater and ray lunar studies, and has been the key to partly pattern, being completely developed on the unravelling the Moon's structure, history, mare and not filled or embayed like Archi- medes, show that they are younger than the mare; some rays are on the mare inside * Contributed by Don E. \\"ilhelms, U. S. Geo logical Survey, i\lenlo Park, California. Publica Archimedes. Thus we have five discrete rock tion authorized by the Director, U. S. Geological units in an ascending age (stratigraphic) Survey. column: rugged highlands, light plains, I 'TEIU'RETATlON OF EXTR.\TERRESTRIAL lM.\GERY 481
FIG. 1. Archimedes region, illustrating age sequence of lunar geologic units. The dark smooth (mare) area (upper left-northwest) is part of Mare Imbrium; part of Apennine Mountains in lower right corner. Archimedes is the large (80 km) marc-ftlled crater. The other two large craters are Autolycus (top) and Aristillus. One of the best Earth-based photographs ever made, taken by H. G. Herbig with the 120-inch reA ector, Lick Observatory.
Archimedes materials, mare materials, young in diameter) was demonstrated beyond crater materials. These relations demonstrate reasonable doubt by Shoemaker (1962), who the important fact that the mare is not only showed that the pattern of secondary craters younger than the rugged terra but is enough around Copernicus is accounted for to the younger to have given time for the light plains last detail by ejection of the secondary crater and Archimedes to form before the mare producing fragments by energy from a point formed. source within Copernicus. And in general, the Interpretations of the origin of the lunar large extent and radial symmetry of hum materials have been made from their surface mocky material (near the ri merest), radial characteristics and lateral distribu tion. These grooves and ridges (farther ou t), secondary materials are concluded to be complexly craters, and above all of the rays that extend interbedded layers of volcanic and impact great distances from large young craters origin. A fragmental layer forms on all ex demonstrate an explosive origin. That the exposed surfaces, its depth varying with the explosion was impact-produced can only be age of the surface. reasoned not proved, but it is difficult to con Craters, specifically, are doubtless of hoth ceive of the containment of sufficient volcanic impact and volcanic origin. The craters along energy long enough to be released all at once. Hyginus rille (Figure 2) are an example of the The circular mare basins also are believed volcanic; they are so regular in spacing and to be of impact origin, judging from their size that they must have formed by volcanic great size and from resemblance of the ex action localized along the rille (graben). Other tcnsi\·e mantling deposits surrounding the volcanic craters are those at the tops of hasins, such as the deposit on the Apennine shieldlike domes. Mountains, to impact crater ejecta. However, The origin of craters by impact is deduced the mare and light-plains materials that fill as follows: first, an explosive process is shown the basi ns and other depressions are probably to have formed the craters, and second, im volcanic, judging from their great lateral ex pact is reasoned to be the explosive process. tent (and discounting unlikely origins such as The explosive origin of Copernicus (90 km. water-laid sediments). Moreover, many of 482 J'1I0TOGI{A~1 ~IETRlC ENG I NEEk[ NG
, FIG. 2. Hyginus rille (Rima Hyginus). The chart (by .. Air Force Aeronautical Chart and Informa tion Center) was compiled from many Earth-based photographs with critical detail added from visual telescopic observations and shows the rille and its chain of craters hetter than any single Earth-based photograph. The inset is from a moderate-resolution (approximately 400 m) Lunar Orbiter IV photograph and shows the rille approximately as it appears when observed visually with a large telescope on a good night. The chart and the inset include a field 175 km long.
these dark and light volcanics are believed to in terpretation of telescopic photographs. be flows because they terminate abruptly Spacecraft data have confirmed some obser against higher topographic forms. vations and interpretations and have modi A considerable amount of information fied others, as discussed in another section about the history and formation of the (vVilhelms, this paper). ]\loon's surface thus has been gathered by
THER~IAL MAPPI:\G OF THE MOON*
THE CO:\TSTRUCTION OF an oscillographic measurements, made in 1963, used a mercury thermal image of the ]\loon was first at doped germani u m photodetector wi th a 10 to tempted by Sinton at the Lowell Observatory. 12 micron filter. The Moon was scanned in a Using a Golay cell as an infrared detectOl', he rastel' fashion with a resolution of about scanned the Moon with a resolution of 1/60 1/200th of its diameter and the infrared signal the lunar diameter. The resulting image, recorded on magnetic tape (Saari and Short however, lacked sufficient detail; his results hill, 1967). These measurements were made \,"ere displayed as a series of isothermal con at 23 different phases through a lunation. A tour charts (Geoffrion, et al., 1960). Recently, similar set of measurements were made during infrared images have been published for the the lunar eclipse of 19 December 1964. The full Moon and for the penumbral and umbral objective of this infrared research is to study phase of a lunar eclipse (Saari, et al., 1967) the thermophysical properties of the lunar and for the third-quat'ter Moon (Salisbury surface. Much of the data reduction has been and Hunt, 1967). done with the aid of computers; large iso Two examples of our lunar infrared images thermal contour charts were drawn and used will be presented here, one of the full Moon, for detailed quantitative analysis (Shorthill and one during totality of a lunar eclipse. The and Saari, 1965). I mages reconstructed from the line-scan data were found to be useful adj uncts to our analysis because they were * Contributed by J. 1\1. Saari and R. W. Short hill, Boeing Scientific Research Laboratories, helpful in visualizing the global thermal Seattle, Washington. patterns on the Moon. INTERPRETATION OF EXTR.\TERRESTR1AJ. 1~IAGERY 483
FJG. 3. An enhanced infrared image of the full Moon at 23 1134.3 M UT, 18 December 1964 (phase angle 2°16'). North is inclined at 30° to the left of vertical in both figures.
Full N[oon: The infrared images were con flat image similar to a visible photograph was structed by intensity modulating an oscil obtained. This filtering technique, however, loscope using the recorded analog signal produced a deficiency in the image, in that while applying the proper horizontal and the limbs were made over-bright. vertical defection voltages (. aari, etal., 1966). The brighter circular regions on this image An image of the full Moon is shown in Figure are the maria (visible albedo~0.06), which 3. The variation in brightness temperature are warmer since they absorb more of the on this image can be understood in terms of incident solar radiation. The uplands (visible the solar radiation falling on the surface, the albedo~0.12), darker on the infrared image, local inclination of the surface and its visible are cooler, as are the bright ray craters (some albedo. The incident solar radiation, which is show up as small black dots). To the left of almost completely absorbed, is reradiated at center and about ten scan lines in diameter is infrared wavelengths. Thus, at full :vroon the the ray crater Copernicus. I ts system of brightness temperature of the subsolar poin t bright rays is observed to be cooler than the is abou t 398° K and decreases to approxi surrounding mare material. The large circular mately 3200K at the limb. Variations in local feature (about 1/5 the lunar diameter) in the slope and changes in the visible albedo ac upper-left quadrant is J\lare Imbrium. Varia count for small differential' in brightness tion in contrast within Imbrium may indicate temperatures of the order of lOOK O\'er the different stages of lava flow as some observers disk. Because of the large signal difference have suggested. The dark outline around the (~800K) between ~hc subsoJar point (center) right edge of Imbrium is caused by the high and the limb, the image was electronically visible albedo of the mountains, combined enhanced to bring out these small brightness with the low inclination of the Sun on the temperature differences presel~t over the inward slopes. This same effect can be seen on surface. The low-frequency conlponent was several of the large craters (i.e., Copernicus). removed wi th an appropriate fil ter and high Eclipsed Jlroon: The most interesting image frequen.:y emphasis was employed, so that a revealed by the data is shown in Figure 4. 484 PllOTOGI{'\~I~IETl{IC ENGINEEIUNG
FIG. 4. An infrared image of the eclipsed moon at 2H I8.8M UT, 19 December 1964. The bright circular feature centered 30 scan lines from the bottom is the ray crater Tycho, a major hot spot. In the lower left corner the bright region in the sky is caused by thermal radiation from the telescope.
This vividly presents the heterogeneity in the quadrant on the image). In addition to the thermophysical properties of the lunar sur 1,000 hot spots found, portions of or all of face and was obtained during the totality of certain maria are also observed to be therm the lunar eclipse. No image enhancement was ally enhanced during the eclipse. needed because of the relatively large changes In conclusion, it must be stated that in in signal obtained over the lunar disk. The frared images of the Moon furnish only hundreds of "hot spots" (white dots in the qualitative information. For studying the image) have been for the most part identified thermophysical properties of the surface, it is as visibly bright craters, many of which are necessary to do precision radiometry to ob associated wi th craters smaller than the tain reliable brightness temperatures. How resol ution of the instru ment (Shorthill and ever, infrared images, two of which have been Saari, 1965). The image shows that the hot presented here, are useful as an aid in the spots are non-uniformly distributed on the analysis of our large thermal con tour maps lunar hemisphere with a concentration in and in visualizing the distribution of the hot are Tranquillitatis (in the upper right spots.
LUNAR AND PLANETARY PROBES SURVEYOR SPACECRAFT*
SURVEYOR I WAS successfully soft-landed on Analysis of these pictures has been described the lunar surface June 2, 1966 and returned recen tly in this journal by HoI t and Morris over 11,000 television pictures to Earth. (1976) and Batson (1967). Surveyor II, launched September 20, 1966, crashed into * Summarized from Vrebalovich and Jaffe (1967), Shoemaker et at. (1967a, 1967b) and Jaffe the Moon on September 23, 1966. et at. (1967). Surveyor III soft-landed on the Moon on I TERPRETATlO OF EXTRATERRESTRIAL IMAGERY 485
April 19, 1967, and returned 6,315 television and Oceanus Procellarum. Differences be pictures. The distribution of craters and rock tween surface layers in these maria a,'e rela like features near Surveyor II [ was found to tively small. be similar to that observed by Surveyor 1. Surveyor V landed in a dimple-shaped, 9 Blocks up to 4 m. long were visible from the by 12-meter rimless crater, which is the spacecraft. Some of these were angular or largest member of a small chain of rimless flat; others were more rounded. Sizes of craters; a parallel row of very small craters individual visible particles extended down to also occurs within the large crater. On the the 1.0 mm. resolution limit of the camera; basis of its shape and the alinement of small over 85% of the exposed surface consisted of associated craters, the crater in which Sur unresolved ftner material. As in the Surveyor veyor V landed may have been formed by I photos, no examples were found in which a drainage of surficial fragmental debris into a fragment seemed perched on a pedestal, as northwest-trendi ng fissure. reported from the Luna IX pictures. It is Observations of block-ri mmed craters, believed that the pedestals reportedly ob ,'elatively nearby, indicate that the local served in Luna IX pictures are illusions that thickness of the layer of fragmen tal debris are, in part, due to the lower resolution of the wi th low cohesion is not more than 5 meters. Luna IX pictures and to the particular con The walls of the Surveyor V crater provide ditions of illumination under which they were exposures of the upper meter of this debris taken. layer. Di fferen t types of fragmen ts are re Television observations with color filters vealed in the pictures of the debris dislodged indicated that the Moon is gray. The local from these walls during the spacecraft land albedo of the fine-grained undisturbed surface ing and in the pictures of the undisturbed was estimated to be 8.5%± .2% (Vrebalovich parts of the walls. The types of fragments and Jaffe, 1967). include (1) bright, angular objects, which are urveyor III landed in a crater about inferred to be pieces of dense rocky material; 200 m. in diameter and 15 m. deep in Oceanus (2) dark, rounded objects, which are probably Procellarum. By close comparison of the aggregates of very fine-grained particles; and Surveyor III pictures with a Lunar Orbiter (3) dark, lumpy objects, which appear to be III photograph of the Surveyor III landing aggregates of aggregates. The aggregate site, it is possible to identify more than 100 character of some of the loose, ejected frag craters and large blocks that are recognizable men ts is well demonstrated by the presence of in both the Surveyor and Lunar Orbiter bright, angular chips set in a dark, fine pictures. Because the number of these is so grained matrix. large, it was possible to use the information The estimated normal albedo (normal obtained from the two different sets of luminance factor) of the undisturbed parts of pictures to produce a topographic map of the the lunar surface near Surveyor V is 7.9± 1.0 crater by methods analogous to ordinary field percent, somewhat lower than that observed surveying, after a solution was obtained of at the Surveyor III landing site. Debris the orientation of the Surveyor I II camera ejected on the lunar surface in front of the (Shoemaker, et al., 1967a). footpads has a normal albedo of 7.5± 1.0 Surveyor IV, launched July 14, 1967, was percent, which is only about one-twentieth unsuccessful in making a soft-landing; its lower than the albedo of the undisturbed retro motor exploded shortly before lunar surface, bu t is si milar to the al bedo of the touchdown. material disturbed by the footpads at the Surveyor V, which soft-landed on the 1\1 oon Surveyor III landing site (Jaffe, et al., 1967, on September 11, 1967, has retu rned over Shoemaker, et aZ., 1967b). 19,000 pictures. The area of southwestern Surveyors VI and VII, the final two Mare Tranquillitatis in which Surveyor V Surveyor spacecraft, ha\'e made successful landed appears generally similar to the sites in soft landings on the Moon and ha\'e returned Oceanus Procellarum observed by Surveyors high q uali ty television pictures as well as J and III (FigUl'e 5). All three areas are faidy information about the composition of the level, dark maria with rather similar distribu lunar surface from magnetic and alpha back tions of craters and rocks. A surface layer of scattering experiments. Analysis of the data weakly cohesive fine particles, aggregates, from these most recent flights is currently in and rocks is present in 1are Tranquillitatis progress. 486 PHOTOGRAMMETRIC ENGINEERING
FIG. 5. Mosaic of narrow-angle pictures from Surveyor V showing the northwest wall of the crater in which the spacecraft is located and the far field beyond the rim of the crater extending to the horizon. (NASA photo.)
GEOLOGIC I~TERPRETATION OF LUKAR ORBITER PHOTOGRAPHS* T HE EXTRAORDINARILY successful Lunar Fh-e Lunar Orbiter missions flew success Orbiter project has produced a rich photo fully out of five attempted, a remarkable graphic data bank that is greatly increasing record, especially since they flew nearly on geologic knowledge of the Moon and will schedule. Lunar Orbiter I (August 1966) continue to do so for years to come. Because photographed 9 potential Apollo landing sites of the wide areal coverage-nearly complete selected on the basis of Earth-based photo for the whole Moon at 500 meters resolution graphs and telescopic observations in the or better, nearly complete for the Earth equatorial belt; it also photographed a num facing side at 70 to 200 meters and very ber of supplementary sites. During the extensive at 1 to 20 meters-Orbi ter photos photographic portion of the mission, periapsis serve as the con text in which to place data (nearest approach) fell near the Apollo bel t from spacecraft missions such as the Surveyor and a\-eraged 52 km. altitude, and apoapsis and the projected manned Apollo missions. (highest point of orbit) came on the far side This discussion will briefly show how Orbiter and averaged 1,850 km. altitude. Resolution refines the basic geological framework inter of abou t 8 meters was achie\'ed on the Earth preted by Earth-based telescopic means, side medium resolution photographs, but the mainly by the U. S. Geological Survey, dis failure to achieve the proper image-motion cussed in an earlier section (vVilhelms, this compensation for the high-resolution system article). Quantitative photogrammetdc re caused unacceptable smear of the high sults, still preliminary, will not be discussed. resolution frames-the only significant failure of the en tire program. However, excellen t * Contributed by Don E. Wilhelms, U. S. Geo photographs were obtained of the far side, logical Survey, Menlo Park, California. Publica tion authorized by the Director, U_ S. Geological including the famous frames with the Earth Survey. in the background. Lunar Orbiter II (Novem- INTERPRETATIO T OF EXTRATERRESTRIAL IMAGERY 487
ber 1966), a similar mission, was almost indicated age relations like those at Archi completely successful and contributed the medes, where young mare material embays most of all missions to speci fication of Apollo and fills an old crater, but Orbiter photo sites,S of the 13 photographed becoming graphs of the Flamsteed ring (Flamsteed P) prime sites. It also contributed the famous prod uced a surprise that led to new knowl oblique photograph of the crater Copernicus. edge of lunar surface processes. Orbiter I NIission III (February 1967) differed slightly showed a com'ex moulding all around the from the first two in that the orbit was in Flamsteed ring that is clearly superposed on clined 21° to the equator in order to explore the mare and so is younger (Figure 6). This additional sites, including several photo relation could be interpreted to mean that the graphed at an oblique angle because of the ring itself was younger than the mare and success of the Mission II Copernicus oblique. therefore was some sort of volcanic extrusive Mission III added 3 prime Apollo sites and overlying a ring dike (O'Keefe, 1967); but many other sites of scientific interest; its only since such mOll/dings are also present around failure was in lost frames in some of the many contacts of mare with rugged objects, eastern si tes. including many diverse forms difficult to These three missions ftlled most of the explain by volcanism, the more reasonable direct Apollo requirements and left the re hypothesis is that the surface material on old maining two largely for scien tifLc purposes terrain is a mobile fragmental layer that (which of course also apply to Apollo). migrates downslope through the effects of Mission IV (May 1967) was of a type en gravity in a lunar manifestation of the process tirely different from the first tht-ee and unfore called mass wasting. Such mass wasting seen in the design of the spacecraft. Tts al probably explains the relati"e paucity of ti tude (approxi mately 2,700 km. periapsis, small craters on slopes relative to plains, also 6,100 km. apoapsis) and orbit inclination the re,-erse of what is expected from the gross (85°) allowed it to survey the entire front side age relations. Thcse obseryations (1) set of the Moon, which it did with stunning limits on the engineering properties of lunar success, except for a fogged strip 10° wide in surface materials, and (2) show that astro the east, in the face of greater difficulties than nauts will seldom find in-place rock outct"Ops faced in any other mission. This is the si ngle to sample in old terrain but will easily be able mission that, because of its wide cO"erage, will to sample the a,-erage composition of a rugged probably prove to have the greatest ultimate terra by sampling the float at its base. value to lunar studies, although its yalue Ft"Om the apparen t abrupt termination of would have been greatly reduced without the mare material against terra observed tele earlier and later high-resolution missions. The scopically, it was early reasoned that the mare greatest achievement of Mission IV was per consisted of yolcanic flows and the wide areal haps the photograph of the Orientale basin extent of the presumed fIo,,'s suggested, (Fron tispiece), taken near the end of the through analogy "'i th terrestrial rocks, ei ther photo mission. Mission V (August 1967-only basalt or ash-flow tuff. Surveyor V and VI a year after Mission 1) was another largely observations apparently indicate a basaltic scien tific mission and an extraordinarily composition for the maria, and Orbiters IV productive and successful one, the most and V have conflrmed that flows are present nearly flawless of all Lunar Orbiter missions by photographs of very clear flow fronts in despite the fact that it, too, flew an 85° orbit, 1'Iare Imbrium (Figure 7) (previously indi which the spacecraft was not designed for. rt cated but not prm'ed in excellent telescopic supplemen ted the other Apollo-orien ted mis photographs). The presence of more than one sions by adding another possible site and by flow indicates an extended and complicated providing high-resolution stereoscopic co,- history of marc emplaccment, as expected erage for four prime Apollo sites selected by from the delayed filling of 1'Iare Imbrium de earlier missions. duced telescupically and from experience 011 Cross geologic (rock or age) units are Earth, "'herc "cry little happcns cataclysmic recognized on Earth-based photographs and ally. finer-scale ones on Orbiter photographs. The 1'lany c"cnts 011 the 1'100n do happcn Orbiter-deri"ed units commonly are com cataclysmically, in particular the formation posed of surficial materials that show age of many craters, as discussed in an earlier relations opposite to those among the gross section (\\"ilhelms, this paper). ]\[any geo units on which they are developed. For ex logists, howe"er, ha,-e resisted this fact, ample, telescopic studies of the Flamsteed presumably because of their experience with region, landing site of Surveyor T, clearly Earth geology-or "'hat seemed to be their 488 PHOTOGRAMMETRIC ENGINEERING
FIG. 6. Part of the Flamsteed ring, showing convex moltldings at base of slopes. Lunar Orbiter II I moderate resolution photograph; site was also photographed by Orbiter I and the ring appears in the distance in Surveyor I photographs. Framelet width is about 1.8 km (NASA photo.) experience. As the impact origin of many but the most fanatic impact proponents to be lunar craters is being demonstrated, more volcanic (or more generally, internal) in and more impact craters are being found on origin, and this belief has been confirmed Earth as well. The 1\Toon, however, is still beyond a shadow of a doubt by Orbiter where the big ones are found. I mpact craters photographs. An example is the craters along range in size from tiny ones observed on high Hyginus rille, discussed in the section on resolution Orbiter photographs through tele mapping (\\'ilhelms, this paper), known and scopically observed craters such as Coper interpreted as volcanic in origin before nicus to mare basins such as Imbrium and Orbiter; this origin was only confirmed by Orientale (to be discussed below). Orbi ter. I t must be emphasized that many of the Other fascinating features of internal smaller craters have long been believed by all origin are sinuous rilles, river-like objects
FIG. 7. Lobate flows in 1\Iare Imbrium. Lunar Orbiter V moderate resolution photograph. Framelet width is abollt 5 km. (NASA photo.) 1NTERf'RETATJON OF L\.TRATERRESTI FIG. 8. Sinuous rilles near the parLly buried crater Prinz. Lunar Orbiter IV high resolution photograph. Framelet width is about 14 km. (NASA photo.) \\'hich, with few exceptions, had been loa structural basins that are similar but lack poorly seen before Orbiter to establish their mare filling.) Fresh exposures in Orientale of mode of formation, now known to be by some structures and geologic units that are eroded flow mechanism still not understood in detail, and cO\'ered in older basins show what is to be and not by faulting (Figure 8). expected in lhe other basins, such as Im Another way in which Orbiter photo brium. Four rings of peaks surround Ori graphs help interpret Earth-based observa entale, and intcrestingly similar but more tions should be mentioned. Several craters, subdued and more deeply co\'ered ones occur crater chains and other objects were selected in the other basins-in about the same to be photographed by Orbi ter partly because spacing. The inner ring of islands in Imbrium they show an anomalously high signal in the was once thought to ring an inner deep basin thermal region of the infrared at eclipse. One like, say, the cratel' Copernicus; now it is seen interpretation of this anomalous signal was that the inner basin probably lies somewhat that an insulating layer apparen tly presen t inside this ring and is relatively shallow. The over most of the Moon was lacki ng and fresh third ring corresponds to peaks covered by rock might be exposed, and indeed high Archimedes rim material, as discussed in an resolution Orbiter photographs show many earlier section (Wilhelms, this paper). large fresh rock fragmen ts at every such The continuity and regularity of the rings infrared anomaly photographed. Such fresh of Orientale and therefore Imbrium show that rock was sought by Orbiter because it will each of the e craters is a unified structurc provide valuable samples to be collected by whose origin centered about a point-an astronau ts. origin easily explained by impact (of an A final lunar feature to be discu sed here is object only a few miles in diameter) but perhaps the most spectacular of all photo difficult to explain by an internal mechanism; graphed by Lunar Orbiter, the Mare Orien a pre-caldera dome, for example, would have tale basin (Frontispc.), barely reae-hed by to have been of enormous height to collapse Lunar Orbiter IV before its picture-taking and form the present ring structure. The ability gave out. The importance of Orientale surface materials also suggest impact origin. in lunar geologic studies is that it is the fresh Most interesting is the outer ridged and est object at the upper end of the impact size grooved material first seen in Orientale scal a mare basin, that is, a large circular (McCauley, 1967b). Comparison of ring crater surrounded by multiple rings and structures between basins shows that this partly filled by mare material. (Orbi ter corresponds in position to material on the photographs of the far side of the ]\\ oon show flanks of the Apcnnine Mountains, long 490 1'.1I0TOGR.\1I1111ETRIC ENGINEEI{1NG Orientale supports the impact origi n of Imbrium. Orientale's freshness provides an additional opportunity to interpret origins from photo graphs. Since the features superposed on the young Orientale are known to be young, the crater shown in lower right of Figure 9 must be young; but it lacks the hummocky ter races, radial ridges and grOO\'es, and secon dary craters of the large craters discussed above and of the crater near it (upper left corner of photograph). Therefore, wi th the variable of age better known than for other craters, a caldera origin is here very strongly supported and criteria for recognition of other calderas can be developed (McCauley, 1967b). In summary, it should be clear from the foregoing discussion that no single, simple origin of lunar features can be invoked to explain all lunar features; volcanism and impact have both played a role. This fact should always have been assumed, and was well demonstrated by Earth-based means, but it has been spectacularly confirmed by the highly successful Lunar Orbiter program. I t remains to establish the relative propor FIG. 9. Floor of Orientale basin including young tions of impact and volcanic features and to probable volcanic crater (lower right quadrant) and part of young probable impact crater (upper determine exactly how these two processes, left). Lunar Orbiter IV moderate resolution photo along with mass wasting, radiation, tecton graph. Framelet \\-idth is about 12 km. (NASA ism, and other processes, have shaped the photo.) surface of the Moon and at what time in the history of the Earth-Moon system it all took believed to be impact ejecta from the giant place. Photographs from Lunar Orbiter and I mbri u m basi n-crater. The Orien tale ma those to be taken by future orbiting space terial, to have such streaked texture, must craft will be the principal tool for doing this. have been emplaced by a great outward rush Data acquired by other means can be fitted to of material such that could hardly have been the framework provided by the Orbitel' produced by volcanism; even though the missions, and Orbiter will show the way for details of texture around the older eroded manned exploration to sample localities likely ImbriUIll are not clear, the analogy with to yield diagnostic material. PHOTOGRAPHIC SENSORS FOR THE DETECTION OL' PAST AND PRESENT EXTRATERRESTRIAL LIFE* PRELIMINARY WORK BY Air Force Cambridge VI traviolet photography in the 3,90oA- Research Laboratories' Terre trial Sciences 4450A spectral region is accomplished by Laboratory in the continuing investigation of using Kodak 5424 film with Wratten 36 and the application of remote sensors for geolog 47 B fi! tel's. Carbonates (limestones, etc.) ical research has suggested two films and have a higher reflectivi ty in this spectral spectral regions amenable for the possible region than any other common rock. On detection of past and present life on other Earth, carbonates are a ubiquitous sedi planetary surfaces. The two types of photog men tary rock. Large deposits al most in raphy are ultraviolet and false color (color variably contain fossils of marine organisms, infrared, camouflage detection). and most large carbonate deposits were formed in a marine environment. Extensive * Contributed by R. S. Williams, JL, Air Force Cambridge Research Laboratories, Bedford, Mas areas of carbonate exposure on other plane sachusetts. tary surfaces would strongly suggest former Il\TERPRETATJON OF EXTRATERRESTRIAL J:I/.\l";ERY 491 oceans and the presence of aqueous organ 50001\ and 8500A. Nonhing matter on Isms. Earth is recorded as a bluish green color. False color photography was specially Living Rora from higher order vascular plants developed to differentiate, by color change, to lower order lichens and algae are recorded between living Rora and ersatz Rora (camou as a reddish-orange color. False color photog Rage). False color photography is obtained raphy is an accurate diagnostic tool in dif with Kodak 8443 film with a \\'ratten 12 filter ferentiating between living and non-living plus an emulsion balance filter. The spectral matter on the Earth's surface. region covered lies between approximately BIBLIOGRAPHY Abel, G. 0., Aller, L.H., Czyzak, S., Ilenize, K. G., Mapping," ill l11alltles of the Earth and Terrestrial Kaler,]. B., Liller, W., Minkowski, R., Munch, Planets, New York and London, .I ohn Wiley & G., O'dell, C. R., 1964, "Planetry Nebulae-A Sons, p. 431-460. Symposium in Honor of Dr. Ira S. Bowen, May McCanley, J. F., 1967b, "Geologic Results from 25, 1964," Publications of the Astronomical Soci the Lunar Precursor Probes," Am. Inst. Aero ety of the Pa.cific, Vol. 76-77, No. 451-454. nautics and Astronautics, AIAA Paper No. 67 Arp, H. c., 1966, "Atlas of Peculiar Galaxies," 862, 8 p. Astroph:ys1:cal Journal Supple'ments, Vol. XIV, Meinel, A.B., 1960, .. Design of ReAecting Tele No. 123. scopes," Telescope, (Ed. G. P. Kuiper and Arthur, D. \V. G., 1962, "On the Problems of B. M. Middlehurst), Chapter 3, University of Selenodetic Photogrammetry," International A s Chicago Press, Chicago. tronomical Union Symposium No. 14, Chapter O'Keefe,]. A., Lowman, P. D., Jr., and Cameron, 12, Academic Press, New York. W. S., 1967, "Lunar Ring Dikes from Lunar Batson, R M., 1967, "Surveyor Spacecraft Tele Orbiter I," Science, Vol. ISS, No..,758, p. 77-79. vision Photogrammetry," PHOTOGRAMMETRIC Pohn, H. A., and Wildey, R. L., 1967, "A Photo El\GINEERI:"G, Vol. XXX[II, p. 1365-1372. electric-Photographic Map of the Normal Albedo Baum, W. A., 1962, "The Detection and \[easure of the Moon," U. . Geological Survey Mi c. 111ent of Faint Astronomical Sources," Astro Geo!. Inv. Map, in press. nomical Techniques (Ed. W. A. Hiltner) Chap Saari,]. :\1., Shorthill, R. W., and Deaton, 1'. K., ter 1, University of Chicago Press, Chicago. 1966, "I nfrared a nd Visible l mages of the Lu nar Bowen, I. S., 1960a, "The 200-lnch Hale Tele Surface During the Eclipsed Moon of December scope," Telescopes, (Ed. G. P. Kuiper and 19, 196-1, Icaru.s 5, 635-659. B. M. l\liddlehurst), Chapter 1, l niversit)' of Saari,]. l\l., and Shorthill, R. W., 1967, "Isother Chicago Press, Chicago. mal and Isophotic Atlas of the Moon: Contours Bowen, I. S., 196/1b, "Schmidt Cameras," Tele through a Lunation," NASA Contract Report scopes, (Ed. G. P. Kuiper and B. M. l\liddle NASA CR-855. hurst), Chapt~r -±, niversity of Chicago Press, Salisbury,]. W., and Hunt, G. R., 1967, "Infrared Chicago. Images: Implications for the Lunar Surface," Bowen, IS., 1962, "Spectrr>graphs." Astronomical !cams 7, 47-58. Techniques, (Ed. W. .'\. H:ltner), Chapter 2, Sandage, A. R, J961a, The Hubble Atlas of Gal University of Chicago Press, Chicago. axies, Carnegie Publications, Washington, D. C. Dieckvoss, W., 1963, "Photographic Proper Mo Sandage, A. R, J96 J b, "The Ability of the 200 tions," Basic Astronomical Data, (Ed. K. A. Inch Telescope to Discriminate Between Se Strand). Chapter 4, U ni versi ty of Chicago Press, lected \\'orld Models," Astrophysical Journal, Chicago. Vol. 133, No.2, pp. 355-392. Geoffrion, A. R., Korner, M., and Sinton, 'vV. M., Sandage, A. R., and Miller, W. G., [966, "A Search 1960, "Isothennal Contours of the Moon," for a Cluster of Galaxies Associated with 3c 48 Lowett Obs. Butt. 5,1-15. 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A., 1964, "Detailed Strand), Chapter 6, niversity of Chicago Photoelectric Photometry of the Moon," A stru' Press, Chicago. l10mical Journal, Vol. 69, o. 8, pp. 619-634. Trask, N. J. and L. C. Rowan, 1967, "Lunar Orbi Wildey, R. L., Schlier, R. E., Hull, ]. A., aud ter Photographs: Some Fundamental Observa Larsen, G., 1967, "An Operational Theory of tions," Science, Vol. 158, p. 1529-1535. Laser Radar Selenodesy," Icarus, Vol. 6, No.3, Van Lopik, J., P. M. Merilield, et 01.,1965, "Photo in press. Interpretation in the Space Sciences," PHOTO- Bibliography of Computer Programs The ASP bibliography of computer pro the intent of reducing computer programming grams has been updated by the Committee costs and man-hours by keeping photogram on Compu tational Photogrammetry, and a metrists informed of existing programs. The listing of the contents is available at the listing reveals that considerable amounts of American Society of Photogrammett·y, 105 ti me and money are lost each year through N. Virginia Ave., Falls Church, Va. 22046. duplication of efforts. The enthusiastic When it was originally compiled, this bibli response and assistance which the Committee ography was limited strictly to those com has received in updating the list (as com puter programs involving photogrammetry. pared with the response during the original However, in updating the contents, the compilation) indicate that photogramme Committee has broadened the scope to in trists are becoming aware of the savings pos clude many programs which might be used sible. in support of photogrammetric programs. As If you have computer programs which you an example, programs have been included would like to include in this bibliography, or which convert latitudes and longitudes into if you would like additional information con grid coordinates, and vice versa. cerning it, please contact the Society. The bibliography has been compiled with Articles for Next Month Dr. J. M. Anderson, Block Triangulation by ISP Commission III. Dr. Sidney Bertram, The Dr AMACE and the Automatic Photomapper. J. M. Burnham and P. R. Josephson, Color Plate Metric Stability. C. E. Olson, L. W. Tombough, H. C. Davis, Inventory of Recreation Sites. J. T. Parry, W. R. Cowan, J. A. Heginbottom, Color for Coniferous Forest Species. F. B. Silvestro, Object Detection Enhancement. Dr. B. Shmulter, Triangulation with Independent Models. Prof. J. Vlcek, Systematic Errors of rmage Coordinates. Paul R. Wolf, Trilaterated Photo Coordinates.