Impact theories, led by lunar authority Harold C. Urey and constituting the majority of American astronomers, hold that the moon was formed as a cold body, that its seas (maria) and craters were molded by the crashing of massive meteorites or asteroids, and that it has been the scene of little, if any, volcanic or other activities such as have shaped the earth's surface. They are profoundly skeptical of the occasional reports of changes oractivities on the lunar surface and tend to reject them out of hand.
For twenty minutes, Greenacre and his co-worker, Edward Barr, watched the distinct patches sparkle and grow brighter as small white dots appeared to flow along them. "I thought the motion seemed familiar somehow," Greenacre said recently in his slow drawl. "Finally it occurred to me that it looked exactly like the sign in front of a supermarket in Flagstaff--dots of red and white lights are chasing each other across it."
The two reddish-orange patches, one sparkling over an area of about 1.5 by 5 miles over a domelike structure and the other about 1.5 miles in diameter on a hilltop, appeared near the Cobra Head widening of Schroter's Valley.
The third spot, a pinkish streak about 1.5 by 11 miles in area, extended along the inner rim of the crater Aristarchus itself.
About Valles Schroteri:
A large sinuous valley, resembling a dry river-bed with numerous meanders. It starts in the crater to the right of Aristarchus, then widens to 10 km, several times changes its direction, then narrows down and finally, at a distance of about 160 km from its origin, it disappears. The floor of the valley is flat and a very narrow sinuous rille, which is not visible from the Earth, zigzags along it. (Section 18)
Larger gif, click below:
Observations of activities in Schroter's Valley have been claimed a number of times in the past. For this reason the British observers, H. P. Wilkins and Patrick Moore, wrote in their book, "The Moon," that "Schroter's Valley is, indeed, one of the most interesting formations on the entire moon." In the Nineteenth Century, F. von P. Gruithuisen and H. Klein had noted an occasional greenish color in the area. At the turn of the century, W. H. Pickering reported seven tiny craterlets in the valley, which he believed to be subject to periodic obscurations by whitish clouds or dust. He interpreted these as definite indications of a large active volcanic area. On February 10, 1949, using an 18-inch reflector in Norwich, England, F. H. Thornton noticed "what seemed to be a diffused patch of thin smoke or vapor, apparently originating from the east side of the valley near Cobra Head, where the landslip is, and spread over the edge onto the plain for a short distance. Every detail of the valley was perfectly clear and distinct except where this patch occurred, but there the definition was poor and very blurred."
Greenacre's observations of "color phenomena," reinforced by subsequent events occurring on the night of November 27th have stood the skeptical astronomical world on its head and stirred the hopes of thwarted lunar vocanists, whose claims that the Moon is one vast, globe-encircling volcanic field are usually met with raised eyebrows. Furthermore, the Flagstaff events may ultimately force changes in plans for Apollo and later lunar landings and exploration.
"My first thought was 'the Russians got there ahead of us.'" Greenacre continued. "Then I kept getting a sinking feeling--something must be wrong--it could't really be happening. After it's all over, you feel stupid of course, to think of all the things you could have been doing but didn't." It was just bad luck that the camera attached to the Lowell telescope had been left out of focus the night before. Knowing that it might take five minutes to focus it under the only fair seeing conditions at the time, Greenacre had to concentrate on visual observations, alternating with Barr at the telescope.
A most cautious and accurate observer, according to John S. Hall, the director of Lowell Observatory, Greenacre has not once mapped a feature in the region of Aristarchus that later had to be removed. The Flagstaff events have convinced him that "the spots indicate some kind of activity on the lunar surface. They were not anything like dust or gas clouds but must have been something changing color on the surface." Greenacre's superlative skill plus his built-in skepticism make this rather laconic statement into one of perhaps historic importance.
On the evening of November 27, Barr sighted two similar red spots in the same location while he was using the same 24" refractor, the instrument with which Percival Lowell had done much of his controversial work on the inner planets at the turn of the century. Barr summoned Greenacre, Hall, and a number of other observers to view the second "color phenomena," which consisted of 1.5-by 12-miles red streak on the exterior rim of Aristarchus and a small patch on a hill at some distance, very close to where the smallest spot had been noted on October 29th.
The spots persisted for an hour and a quarter. Meantime, Hall phoned Peter Boyce at the Perkins Observatory in Flagstaff and asked him to look at Aristarchus with their 69-inch reflector, which would not give chromatic (color) aberrations as the refractor might. Boyce confirmed the existence and location of the red streak. This time several bursts of black-and-white photographs were made, but the patches did not appear on them, and in fact could not be seen with the 12-inch guiding telescope attached to the larger one. Color film has now been tested and readied to record any future patches.
To add to the mystification, the U.S. Air Force report, which was finally published in May, noted that about three hours after both events "violet- or purple-blue colors," which partially covered some familiar features, were observed forming and spreading around the rim and within the crater of Aristarchus. The report explains, somewhat obscurely, that "this portion of the observations has not been published for various reasons, the most important being that there is doubt as to whether they are a part of the red phenomena." It adds rather freely, to the delight of lunar volcanists, that such a haze "has been reported by numerous observers in and around Aristarchus and other craters for many years," and documents some of them. A recent run-down totted up sixty events reported in Aristarchus, of which twenty-five had been fairly accurately dated and described. To top it off, Aristarchus is far and away the most brilliant point on the moon, brightly apparent even when it is lit only by earthlight during lunar eclipses.
Aristarchus (Image by Cidadao)
For 3-D Image, click below
In 1931, a British astronomer, Walter Goodacre, reported a bluish glare on the west wall of the crater Aristarchus just after sunrise; the same glare was noted by other astronomers. In 1945, H.P. Wilkins observed a "bluish glowing of streaks on floor - Aristarchus crater - and a mountain mass delta." The American astronomer, Dinsmore Alter, noted in his observing log book in 1959: "Visual-Interior of Aristarchus is a light brilliant blue!! Later in night it was white again. The observation was made with the Mount Wilson 60" and a power near 700. Seeing was only 2."
Were any spectrograms attempted of the longer second-color phenomena of Aristarchus, or of the bright hazes? There may not have been time, of course. But this is just what Soviet astronomer, N. A. Kozyrev, of Pulkovo Observatory, Leningrad, did on three occasions in 1961 when he saw "brightenings" in Aristarchus. The spectral bands he obtained convinced him that hydrogen gas had been issuing from a cone within the crater. Russian astronomers have usually subscribed to the volcanic theory. If it should turn out to be correct, we will have literally to stay up nights catching up with their extensive lunar geological analyses.
Were any contrasting blue-violet and infrared photographs made of
the purple-blue hazes of Aristarchus? Normally, infrared light will slice
much further through veils, fogs, or hazes than blue-violet light of shorter
wave lengths. If a plate taken in infrared light shows less fuzziness than
one of the same area taken in blue-violet light, the infrared light has
obviously penetrated something.
Using the 60-inch Mount Wilson reflector, Dinsmore Alter made such
photographs of the lunar crater Alphonsus in 1956 and found that certain
features looked more fuzzy on the blue-violet plates than on the infrared.
At the time, this photographic evidence of some kind of obscuration or
"degassing" on the moon warmed up the then lukewarm interest in the issue
of lunar activity.
The fuzzy floor of Alphonsus
Alter subsequently obtained photographs of similar obscurations around Linne on the western side of the Sea of Serenity, drawn by early lunar cartographers as a deep crater four to five miles in diameter. In the 1860's the crater seemed to have vanished and a small whitish hill or dome had taken its place. Whether Linne had ever been a crater or not became a very tangled controversy. In 1961 and 1962 a number of observers noted that Linne' looked very much like a distinct crater on occasion, then later returned to its normal aspect. It is urged that under certain conditions of lighting the slopes and shadows of Linne' are such that it gives the false impression of being a crater; this may have been what the early observers saw. Now Linne' is indubitably a ten-mile, light colored mound with a tiny hole in it. A small dark craterlet near the crater Birt by the Straight Wall in the Sea of Clouds also appeared to Alter to be obscured in some photographs.
The very best EBTI of Linne' Crater, imaged by Cidadao
A small, relatively young crater, 2.4 km in diameter, 600 m deep. It is surrounded by bright ejecta material; under high illumination it appears through the telescope as a bright spot. In the literature, since the second half of the nineteenth century, numerous mysterious changes and disappearances of Linne' have been recorded. These are classic examples of observing errors which occur when lunar details are close to the limit of resolution of a telescope.
Alter remarked of his Linne' photo graphs that "If you compare the difference in the crest of that 10-mile mound with the difference between the other features in the two photographs, you will agree it's too great. To me that suggests the possibility of additional atmospheric obscuration in the immediate area of Linne', which in turn suggests gas seepage there. But that's something each of you will have to decide for himself."
Some astronomers agreed with Alter. Most could see no more than variations in resolution over the whole face of both photographs, caused, they thought, by terrestrial atmospheric effects. But in 1963 Alter wrote that he must "plead guilty to a stubbornness which forces me to remain one of the minority who believe that, despite the great importance of meteoritic impacts on the moon, its internal conditions have been even more important in producing the surface we observe today."
The British astronomer, Patrick Moore, at the New York Academy of Sciences' conference on geological problems in lunar research in New York in May 1964, underlined his belief that "volcanic forces played the main role in the molding of the lunar surface." To illustrate his point he displayed a photograph filled with realistic craters, craterlets, and domes- then confessed that it was simply a picture of a pot of boiling porridge!
Stressing the difficulties that confront lunar observers, Moore said, "In my thirty years of studying the moon, I've only seen one event on it of which I'm certain, and that was really a case of not seeing something. As a youngster using a very small telescope, and really inexperienced, I was sure I saw light spots in Schickard, a large walled-plain near the edge of the moon's face. Others have reported spots or mists there, too, so maybe I did see them, but I don't claim it now. I am certain, however, that one night a number of craterlets in the floor of Plato weren't there where they should have been. I didn't see any distinct haze or anything moving--they just weren't there. Explain it if you can.
Moore has helped to confuse the issue by attributing the "color phenomena" in Aristarchus "to some kind of colored surface deposits, possibly on slopes, visible only under certain conditions of lighting and libratory wobbling of the moon." Hall has also commented that "It is perhaps significant that all four Lowell sightings were made less than two days after the Aristarchus neighborhood emerged into the sunlight." The sunlight might perhaps have simply made the patches visible or caused certain types of material to luminesce.
Many features of certain lunar craters and seas have been pointed out that indicate that volcanics have played a part in the shaping of the moon. The placement of the larger craters and their shapes appear to be related to the grid of surface fractures and faults, rather than being randomly scattered about the moon's face, as meteoritic craters would be. There are many chains of craterlets on the moon, and craterlets are often nested within larger craters as they are in terrestrial volcanic areas. Further, the rims of craters come right up to those of craterlets on them, whereas it would seem that hypervelocity impacts would have devastated the rims where meteorites struck. At least fifty tiny holes have been discovered on the peaks of sharp crater cones or central mountains, which meteorites could hardly have drilled so neatly by chance.
After Alter had announced apparent obscurations of portions of its floor, Kozyrev became interested and began to make routine spectrograms of the crater Alphonsus. In November 1958 and October 1959, he obtained spectra which he interpreted as indicating the outflow of gases, a lava stream, and a cloud of volcanic dust from Alphonsus' central peak.
After the first event in 1959, a tiny red patch on the south side of the central peak of Alphonsus was seen by a number of observers. Among those reporting this new spot of color were G. A. Hole, H. P. Wilkins, and B. Warner in England and several observers in Hungary and the United States. Wilkins saw the patch as roughly circular, with a black spot in the middle and red-colored material mounted around it. However, others who searched for this patch, even with large instruments, could not see it at all. As described, it sounds remarkably like some of the color phenomena in the vicinity of Aristarchus.
In 1961, Kozyrev reported that his spectra of the center of Aristarchus definitely indicated the emission of molecular hydrogen gas from the moon's interior. The luminescence revealed by the spectra of Aristarchus and its vicinity, he also claimed, was much too intense to have been produced by solar-wind particles or by solar radiations, as some have suggested. He concluded that "volcanic processes on the moon, observed so often, show that it has internal energy that can be no less than the internal energy of the earth." He firmly believes that "the history of the formation of the lunar landscape may, in fact, be mainly the history of the internal processes of the moon's cosmic existence; while external influences rnay have been of secondary importance and, in particular, the role played by meteorite impacts scarcely more significant than in the formation of the known terrestrial features."
The heads of the impact people are bloodied but unbowed from the blows of this mounting, substantial evidence. Fred Whipple, director of the Smithsonian Institution's Astrophysical Observatory, expresses the essence of the impact view in writing that "Within a dark lunar cave there would be eternal silence and inaction excepting possibly moonquakes. A spider web across a dim recess in such a cave would remain perfect and unchanged for a million years."
The American astronomer Ralph Baldwin marshaled solid evidence in the 1940's that many lunar craters were formed by impact. He discovered a definite relationship between the depth and diameters of the pits blasted out by terrestrial mines, shells, and high explosives and those of the larger lunar craters-they appeared to fol low the same strict mathematical ex pression, although it has been pointed out that there is a considerable spread in the data. The formation of some of the great lunar craters like Copernicus, Kepler, and Tycho has been analyzed in detail by scientists like Eugene Shoemaker of the U.S. Geological Survey and similiarities to nuclear explosion craters at the Nevada testing site pointed out-even the star-shaped rays extending radially from the lunar craters are faithfully repeated in Nevada. The debris thrown out by impact and the patterns of secondary, peripheral craters created around the primary ones have been studied and explained, and the contrast with the effects of volcanic eruptions has been underlined.
Lunar volcanologists were on the offensive, however, at the lunar research conference in New York in May, explaining lunar seas and craters, rules and highlands in terms of active volcanic shaping in the past. They went so far as to assign a volcanic origin to the Wolf Creek crater (Australia), the New Quebec crater (Canada), and even the Meteor or Barringer crater Flagstaff, Arizona) -show pieces of the impact theorists, for whom Flagstaff has become a veritable plague spot. One geologist asserted that all ten possible meteoritic craters discovered in Canada must be volcanic.
Canton Beals, Dominion astronomer of Ottawa, had perhaps the final word on this particular phase of the controversy: "The universe is rather large and varied and it has plenty of room for more than one type of physical process," he said. "Neither impact nor volcanic theories will win out in the long run. We all need to collaborate on reaching criteria that will distinguish more sharply and reliably between both terrestrial and lunar volcanic and impact craters." Beals' suggestion makes excellent sense to many lunar scientists who are quite sure, for example, that Copernicus is basically a great meteor-impact crater but that many smaller craters even in its neighborhood are volcanic in origin.
Patrick Moore pointed out that "the number of lunar activities reported seems to vary directly with the total amount of time devoted to observation of the moon." He stressed that "further studies are needed before any final conclusion can be reached," and recommended that "a world-wide observational program be initiated at once to keep at least the lunar areas where activity is suspected under constant surveillance."
On this score, James Edson, associate administrator of the National Aeronautics and Space Administration, announced in May the development of a "color-blink" instrument to aid in the discovery of color phenomena or surface brightenings on the moon. Sponsored by the National Aeronautics and Space Administration, it would reveal color changes by adapt ing the principle of the blink microscope. The blink microscope, which identifies variations in the intensity or movement of light, played a role in the discovery of the planet Plato.
Any color phenomena occurring on the moon would be amplified in and appear to pop in and out of the tele scopicimage in the "color-blink" instrument, just as in the blink microscope the photographic image appears and disappears, seeming to "blink." The most complex model will use a color television system to compare two or more telescopic images of the moon automatically, identifying those on which even minute color phenomena have occurred.
Such instruments, only now being designed and developed, would have their limits, of course. The color phenomena that appeared near Aristarchus were not easy to resolve because of the relatively small areas covered by the patches. Greenacre judges that a 16-inch reflector or a 20-inch refractor might be needed to pick out such tiny colored spots as those he saw, since he was not able to detect them in the 12- inch guide telescope at Lowell Observatory. Moore estimates that color phenomena or brightenings like these might be observable with a good 12- inch telescope. Very few amateurs are lucky enough to own instruments as large as twelve inches in aperture. The extent to which the "color-blink" instruments would intensify the color images would also determine how large a telescope had to be used. And instruments of this kind certainly cannot substitute for a constant organized surveillance of these active areas by sizable telescopes across the country, or on an international scale, around the world.
Volcanists suggest that tidal disturbances in the lunar crust may be caused by the gravitational pulling and hauling of the earth. Such tides might bring about the volcanic activities on the moon that they believe cause the "color phenomena" like those around Aristarchus. The nights of June 4 to 6, 1964, offered a first test for this theory, because the effects of the earth's gravity on the lunar crust were the same as they were on October 29, 1963. Unfortunately, the sky was so overcast at Flagstaff, Arizona, on these nights that the moon could not be followed there.
The Amateur Astronomers Association of New York announced, however, that on the night of June 6th dim spots were seen by several amateur observers using an 8-inch reflector at Riverdale in The Bronx, New York. This time two tiny red or reddish-brown specks or smudges were reported between Aristarchus and the nearby crater Herodotus, south of Schroter's Val ley. They were seen simply as colored spots, without the sparkle or motion which had been remarked at Lowell Observatory in 1963, and were difficult to pick out. This observation was perhaps more in keeping with an interpretation of the spots as luminescent phenomena occurring when the sun was rising on the region than as some kind of volcanic activity. But very little detail could be distinguished by such a small telescope, and the observation only tends to confirm the existence of color phenomena in the vicinity of Aristarchus, not to indicate either their nature or their cause.
What bearing do the events in Aristarchus and Alphonsus have on our space programs? The exact limits of the area within which men on the first Apollo excursion are to land on the moon have not been announced. Orbital and propulsive requirements were probably decisive in the choice. It is general knowledge, however, that this area is along the lunar equator, perhaps only a few degrees wide to the north and south of it, and stretching perhaps thirty to forty degrees east and west of the moon's central point, located in the Sinus Medii.
As it happens, almost no lunar activities have been reported in this suggested lunar landing area. Although it is on the border, if not well beyond the proposed landing belt, the Hyginus cleft system, which passes through the crater of Hyginus, located about eight degrees north of the lunar equator, has been found to consist principally of a row of tiny craters and has shown signs of activity. Here, H. P. Wilkins reported that at times white spots appear on the edges of the clefts and at other times a haze or mist seems to obscure the clefts. In reviewing the evidence, Patrick Moore admits that in the Hyginus area "there is a chance that once more we are dealing with occasional 'veiling,' "but he concludes that "personally I have grave doubts."
In addition, in 1878, Hermanii Klein, director of the Cologne Observatory in Germany, reported an apparent remarkable change in the lunar landscape northeast of the Hyginus crater. This was a new, small crater, apparently without a pronounced rim or wall-little more than a depression. A search through earlier maps, drawings, and photographs failed to turn up a record of this depression, later named Hyginus N. Additional study of the area revealed another apparently new, still smaller depression to the southwest, connected with N by a dark band; this was called Hyginus N1.
While Klein's contemporaries tended to accept these craters as new phenomena, it is generally thought now that they had simply been missed by the earlier observers and mappers. Just east of N there is a mountain ridge that throws a shadow and thus makes N and N1 stand out more sharply at sunrise on the moon, giving them the appearance of full-fledged craters. This circumstance is believed responsible for Klein's seeing these craters; his predecessors may not have viewed them under just the right conditions of illumination. Many other supposed changes on the moon may well have been due to similar effects. But the white spots and obscurations in the cleft cannot be explained away in this manner. Hyginus may be an area worth close investigation.
Our lunar exploration plans may have to be changed if, as the Flagstaff color phenomena and other observations suggest, certain regions of the moon eventually are proved to be the scene of volcanic activity. Jack Greene, of the North American Aviation Space Science Laboratory, holds that if most lunar craters and maria are the effect of volcanic activities, then "base selection should be guided by a different set of objectives than if the lunar surface were dominantly impacted." He points out that volcanic terrain offers many tubes, caves, and fissures to provide protection from solar radiation and temperature extremes, as well as mineralization, such as ice or sulfur, and sources for heat, which would not be likely in impacted environments. One of the lunar craters he suggests for a base is Alphonsus, far south of the landing ribbon proposed for the Apollo excursion. We could scarcely afford to bypass areas that contain such assets. The Russians, who have stuck to the volcanic hypothesis and made extensive geological studies of the lunar surface, may be far better prepared than we are to take advantage of this kind of situation.
Fortunately, most of our lunar scientists now seem agreed that there is a pressing need to accumulate and integrate all possible facts about the moon's surface features. Participants in the New York conference on geological problems in lunar research held in May were circularized after the event to determine whether they would "urge that lunar research be pursued on as broad a basis as possible. This research should include studies of laboratory models and terrestrial analogs of such features as nuclear explosion craters, meteor impact craters, volcanic and crypto-explosion craters, calderas, volcano-tectonic depressions, cauldron subsidence structures, and associated tectonic patterns"; in other words, many types of both impact and volcanic phenomena should be investigated.
While the returns from this survey are not yet in, such an open-minded, objective, and co-operative approach, free of the bickering over theory that has hampered lunar research in the past, should hasten the day when the nature of the forces that have molded the moon's surface will be unequivocally established.
For more information check out The Lunascan
Project's web pages for the regions at:
Written by Joseph H. Jackson, produced for Analog, October 1964. Images and some text provided by The Lunascan Project, whose Home Page is at: