Herman Leroy Fairchild: An Early Promoter and Defender of Meteorite Impact Cratering

by

Jutta Siefert Dudley

Originally published in Proceedings of the Rochester Academy of Science, Volume 18 Number 2, November 1998

Herman FairchildIntroduction

Herman Leroy Fairchild’s life, from 1850 to 1943, spans a time of great change in science. The geological sciences were maturing and their importance was becoming recognized. Fairchild played an active role in advancing studies of the earth - as a professor and popular lecturer, as a founding father of the Geological Society of America, an active participant of several scientific organizations, and through extensive fieldwork. Geologists today recognize him for his founding work in American glacial geology, but he made contributions in other areas as well. Fairchild’s participation in the Meteor Crater controversies and his interest in earth origins are not generally well known, although Coon Mountain Controversies (Hoyt, 1987) has somewhat redressed that. The recognition and understanding of impact cratering in the Earth-Moon system took an important leap forward during his life time. His supportive efforts helped propel radical ideas ahead, into the mainstream of thought.

A meteorite strike near home?

One evening in 1894, at a farmhouse in Fishers, Ontario County, New York, the Woolston family heard a roar that shook their home. Had something struck the ground? A search of their property the next morning revealed a huge hole fifteen feet across and thirty feet deep. Dirt had been thrown up in all directions. Recognizing an unusual geologic phenomenon had occurred, Mr. Woolston contacted Herman Leroy Fairchild, professor of geology at the University of Rochester. The next day the professor was at the site exploring the cavity. Soil samples were taken by wagon to the university. Henry A. Ward of Ward’s Natural Science Museum, and his assistant Frank Pugsley of Pittsford, dug away trying to find the meteorite presumed to have created the hole. The digging was not successful and no meteorite was ever found (Fisher, 1987).

Professors Fairchild and Ward were not unfamiliar with extraterrestrial rocks. Ward had by the early 1890s, already amassed and sold, two large collections of meteorites. In 1894 he commenced collecting for his last and greatest meteorite collection (Ward, 1904). His interest in meteorites was both commercial and scientific. Although he did not contribute papers at national scientific meetings, he later wrote a number of articles in the Rochester Academy of Science Proceedings about meteorites in his collections. Fairchild’s acquaintance with meteorites at that point in time was less intimate than Ward’s. However, he would have been familiar with the specimens in the university museum collection as well as the information Ward shared as a fellow member of the Rochester Academy of Science.

The impressions Fairchild and Ward had of their visit to the Fisher crater site and any subsequent studies of the collected soils remain unknown to us today. Diligent searches for references to this site in their personal papers, archived at the University of Rochester, have been unfruitful. The exact location of the former hole is no longer known since it was filled in over the years and has since became part of a housing development. One can question whether the pit was of meteoritic origin, since collapse and even cave-like features have occasionally been reported in this region of the Irondequoit valley (Fisher, 1987). With active gypsum mines not far away, it is conceivable that solution of underlying gypsum deposits caused the Pleistocene sediments to collapse on the Woolston farm.

It is likely that Fairchild’s interest in craters had already been piqued, since two years earlier he had invited Karl Grove Gilbert to speak on such a topic at a gathering of the Rochester Academy of Science (Fairchild, 1892a). The former University of Rochester student, originally a math and classics major, became a geologist after becoming inspired by this field while clerking for Henry Ward. Now a chief geologist for the United States Geological Survey (USGS), Gilbert spoke of his investigation of a huge crater in Arizona, only recently made known to science. The Arizona feature, known as Coon Butte or Coon Mountain to the locals, would, years later, become the focus of a scientific controversy. Fairchild would become more than a bit player in the exchanges that took place. This enigmatic hole in the ground and what it represented for planetary processes would engage his attention and study sporadically over several decades.

A crater surrounded by meteorites is brought to the attention of geologists.

Gilbert heard about the crater in northern Arizona in 1891 from A. E. Foote, a mineral dealer who first recognized the meteoritic origin of the irons strewn around it. Foote wrote about the meteorite finds and commented that no volcanic products were to be found near the crater (Foote, 1891a). The implication of these observations was noted by Gilbert during Foote’s subsequent presentation to the American Association for the Advancement in Science in 1891. Following the lecture, Gilbert suggested that the crater had been created by a "small star" and was similar to the impact depressions on the moon (Foote, 1891b; Gilbert, 1896).

Although meteorite studies had for a century been acceptable topics of study, impact cratering studies were yet in their infancy and still on the fringes of acceptable scientific pursuit. First hand experiences with impacting meteorites was limited, and observations often reported the formation of relatively shallow depressions - not deep craters. The Earth’s craters were recognized as being of volcanic origin (unless they were sink holes), so impact cratering was studied primarily in relation to lunar topography. Nevertheless, the prevailing theory among astronomers held that lunar features were also of volcanic origin.

The opportunity to compare the Arizona crater with lunar craters appealed to Gilbert. He sent his assistant, Willard Johnson to investigate. Johnson reported back that the Coon Butte crater was likely of volcanic steam explosion origin. This conclusion assumed the meteorites on the surrounding plain were coincidental. Perhaps not satisfied with this conclusion, late in 1891, Gilbert decided to see for himself. He was accompanied by Marcus Baker of the US Coast and Geodetic Survey, an expert on magnetic observations. While at the site, Gilbert gathered evidence for two opposing hypotheses- steam explosion and meteoritic impact (Gilbert, 1892, 1893a, 1896). They surveyed the site topographically, geologically, and magnetically for two weeks. Another two weeks were spent in the nearby volcanic San Francisco peaks area, for comparative studies. Collected samples were later studied by petrographers and chemists at the Survey. A promised report on Coon Butte never materialized but his conclusion was shortly made public.

Gilbert described the Coon Butte investigation at professional meetings in Washington, D.C. and again in August of 1892 while attending the American Association for the Advancement of Science meeting in Rochester, New York. His presentation was at the invitation of Fairchild, and under the auspices of the Rochester Academy of Science. Entitled "Coon Butte and the Theories of its Origin," the lecture was advertised as being accompanied by lantern slides (Fairchild, 1892b). He also brought with him a contour model of the crater which he left for the University of Rochester museum (Fairchild, 1892c). None of Gilbert’s presentations were published, so the details are unknown. Fairchild remembered years later that Gilbert had favored the volcanic steam hypothesis during the Rochester lecture (Fairchild, 1928b). His speeches must have formed the nucleus of an important presentation and paper that would follow three years later.

Gilbert repeated his conclusion in an address to the Washington Academy of Science in 1895. His presentation and subsequently published paper "The Origin of Hypotheses, Illustrated by the Discussion of a Topographic Problem," revealed a marvelous adherence to the multiple working hypothesis principle promoted by Thomas C. Chamberlin and the scientific method. His main theme was that "tentative explanations are always founded on accepted explanations of similar phenomena" (Gilbert, 1896). His readers and listeners were treated to his use of analogy to form hypotheses using the Arizona crater investigation as a case study.

Understanding that the irons found near the crater were meteoritic, Gilbert envisioned a falling body from space impacting the earth. The idea was conceived from a model of solar system origin that described planet formation as the falling together of many small celestial bodies. Also, the craterform features left by raindrops in mud or projectiles fired into steel, were analogous to what an infalling asteroid might create on a larger scale. On the other hand, an explosion caused by steam, as concluded by Johnson, was also likely in the context of the volcanism exhibited in the region. It was these two hypotheses that Gilbert wanted to test.

The crucial test, Gilbert believed, would be the absence or presence of a buried extraterrestrial mass. He believed an impact would leave a buried mass below the crater. Lack of such a mass would bolster a volcanic steam explosion origin. Based on these assumptions, Gilbert planned to make several observations. The contents of the rim debris should theoretically be greater than the hollow left behind if a buried "star" is below. Making such a quantifiable observation should prove satisfactory in solving the problem. Since the meteorites in the region are of iron, he assumed the buried mass would be also. He reasoned that detection of the buried iron could be accomplished with a magnetic dip needle, as was done by prospectors in northern Michigan.

A magnetic survey found no variation in direction or intensity in or near the crater. Tests of the equipment later revealed that any buried meteorite must either be much smaller than the crater or buried very deeply. The topography of the area was mapped with an interval of ten feet. This allowed calculations of the volume of rim material and the hollow. The results showed they were equal. The test results seemed to rule out the meteoritic hypothesis. "I did not find the star because she is not there" he later told William M. Davis (Davis, 1926). Little was said about the observations which led to the conclusion that the steam hypothesis was valid. Gilbert mentioned that calculations of the energy released by the heating of water in the sandstone revealed that it could eject fragments to the surrounding plain. Analogies were made to volcanic explosions, in particular to the catastrophic steam events in Japan of 1888. Since the Arizona crater lies close to a volcanic region, this analogy seemed logical. Further analogies were made with the maars of Europe and India which were believed to be of cryptovolcanic origin.

Since the marriage of two ideas is often satisfactorily merged into one hypothesis, Gilbert credits Warren Upham for proposing in 1894 that underground conditions at the Arizona site were ripe for an explosion that was triggered by the impact of the bolide. However, Gilbert firmly dismissed this theory as depending too much on coincidence.

At the end of his 1896 article, Gilbert brought forth some points made by Edwin E. Howell who had studied a collection of meteorites from Coon Butte. The irons are individuals and not broken fragments Howell observed. He inferred they should all be connected somehow and suggested that they arrived in a large stony meteorite. Therefore, if like "plums in an astral pudding," the buried "star" might not attract a magnet even if very large. In addition, the shock of impact may have compressed the rock strata below, thereby occupying less space. Gilbert freely acknowledged this would invalidate his original argument. He pointed out that when a conclusion becomes unsettled, it illustrates the tentative nature of both hypotheses and the results of science.

Gilbert’s declaration of a volcanic steam origin were heard louder than his admission of possible error. His reputation as a fine geologist with the U.S. Geological Survey solidified this conclusion in many scientist’s minds. This mind-set would slow down the revolution that would eventually break the volcanism paradigm that attempted to explain terrestrial and lunar craters.

The volcanism paradigm

By the early 1800s most scientists had accepted the idea of rocks falling to the Earth from space. That these rocks could be large enough to create craters on the moon or earth, however, was not yet generally accepted. Craters from known meteor falls were relatively shallow, so lack of experience with major falls tempered the scientists’ imaginations. On the other hand, craters formed by volcanic activity were well known on the Earth. It seemed reasonable to assume that lunar craters could be created in similar fashion. In the 1830s and 1840s several renowned selenographers and geomorphologists produced works that authoritatively established the volcanic origin of the lunar craters (Marvin, 1986). An impact explanation given by Franz von Paula Gruithuisen in 1829 was not popular but, astronomer Richard A. Proctor revived the impact theory in 1873 in his book The Moon. Proctor reasoned that meteoritic downfalls could have created the lunar landscape because the solar system was thought to have been created by collisions between planetesimals (Marvin, 1986). This was an idea that would capture the attention of Gilbert as well as Fairchild and other earth scientists, as they attempted to explain the origin of the Earth-Moon system. Although careful scrutiny revealed differences between lunar and terrestrial craters, few were willing to give up a known process. The alternative seemed too incredulous.

Gilbert’s study of Coon Butte led to research on volcanism and lunar craters (Gilbert, 1893). Careful analysis of lunar craters and impact cratering experiments confirmed his conviction that lunar craters were of impact origin. He came up with an ingenious explanation for lunar craters. He envisioned the newly forming earth as being surrounded by a ring of moonlets which further accreted to form the moon (Hoyt, 1987, Ch. 3). The last rocks to fall created the lunar topography we see today while on the earth, erosion had long ago destroyed evidence of such impact (Mark, 1987, p. 28).

Gilbert’s astronomical studies were short-lived and not generally known or appreciated by astronomers (Baldwin, 1949, p 64). Since many influential astronomers believed volcanism explained the lunar topography, knowledge of Gilbert’s work would not have changed their way of thinking, just as the work of others in this regard had been disapproved. His foray into lunar studies however was later emulated by his geological contemporaries, Fairchild and Daniel M. Barringer, who would eventually follow Gilbert’s footsteps to the Arizona crater.

Gilbert’s lunar impact idea, minus the moonlets, was mentioned as a footnote in the popular earth science text Geology by T. C. Chamberlin and R. Salisbury (1905, p. 598). These authors imagined the lunar craters as being of an unusual volcanic class similar to Coon Butte. Most geologists were hesitant to join Gilbert in his acceptance of lunar impact cratering. On the other hand, most were willing to agree with his widely known volcanic steam origin conclusion for Coon Butte. The volcanism paradigm had not yet run its course.

A meteoritic origin for the Arizona crater is defended

Daniel Moreau Barringer, a mining engineer and geologist, heard about Coon Butte in 1902 while in Tucson. Samuel J. Holsinger told him the locals believed it had been created by a meteorite. One of them, a local trader named Volz, had been collecting and selling the Canyon Diablo irons scattered across the plain. He had told Holsinger that there should be a meteorite in the crater. The idea of a possible commercially extractable nickeliferous iron mass below the ground intrigued Barringer. Back home, in Philadelphia, he and his physicist friend Benjamin Chew Tilghman, were convinced by the specimens they received from Holsinger, that claiming the site for mining would be worthwhile. In 1903, Standard Iron Company was formed, claims were filed, money was raised, and drilling began, with Holsinger as operations manager. Geologic observations at the macroscopic and microscopic level indicated that no volcanic explosion was possible. A formal letter submitted to the Academy of Natural Science of Philadelphia in September 1905, established their claim that Coon Mt. was of impact origin. They followed up with articles of their findings in the Academy proceedings (Barringer, 1905; Tilghman, 1905). The two articles, in direct opposition to Gilbert’s previous findings, started what is called the "Coon Mountain controversies" (Hoyt, 1987, p. 89). The debates (first over origin, then, regarding the disposition of the meteorite) would essentially end by 1930. Even so, acceptance in some quarters lingered until the dawn of the space age!

Barringer believed the geological evidence collected at the site refuted the steam explosion theory of Gilbert. After a thorough description of the topography and geology in the 1905 publication, Barringer discussed several theories of crater origin. Lengthy points of refutation were given against volcanic or steam explosion hypotheses while the impact origin was advanced. The geologic evidence for meteorite collision was overwhelming. Within the crater, the originally horizontal strata of the Colorado Plateau were uplifted and tilted. In some places sections were thrown out and overturned. Fragments of the strata from depths of 1000 feet were strewn concentrically around the rim and beyond. Huge blocks were found up to a mile away. Very fine silica powder, angular in shape, lay in huge quantities around the rim and in the crater. Meteoritic irons were found concentrically arranged about the crater. "Shale balls," or magnetic iron oxide nodules, were found admixed with other fragments around the rim. The hummocky topography around the crater showed evidence of having flowed as in a splash.

Tilghman refuted the calculations of Gilbert, finding the rim debris to be much less than the volume of the hole. His experiments with broken up magnetite revealed that the absence of a magnetic anomaly could easily be explained by the presence of many meteoritic fragments in the basin. He showed that the iron oxide fragments (shale balls) were chemically similar to the Canyon Diablo irons. They also exhibited typical features of iron melted in flight. Tilghman described the powdered silica, as well as the crushed and fractured strata, as being created by a powerful blow. Experiments with projectiles were described and the roundness of resulting craters, regardless of the angle of penetration, was demonstrated. Drilling deep into the crater showed that meteoritic material was present. Tilghman concluded his article with estimates of the age of the crater as well as the size of the meteorite. He indicated that the object must not have been retarded by the atmosphere, but struck at cosmic velocity.

These facts were significant in establishing the validity of their impact hypothesis and were incompatible with the currently favored steam explosion idea. Nevertheless, these facts were criticized or ignored by those who preferred the less outrageous steam theory, or just preferred to follow in the footsteps of influential USGS geologists.

Fairchild is initiated into the crater controversy

Fairchild visited the far west during the summer of 1906. He wanted to see the effects of the great earthquake in California and planned to attend a meeting in Mexico City later. His long time friend, John Casper Branner of Stanford University, had just been to the crater in Arizona and was quite intrigued by the meteoritic evidence that contradicted Gilbert’s findings. Branner was a friend and mentor of Daniel M. Barringer whom he’d met in 1890 when Barringer served as his geological apprentice in the Arkansas Geological Survey (Hoyt, 1987, p. 75). More recently, Branner had also made the acquaintance of Gilbert as they served on a post-earthquake commission together. Branner urged Fairchild to visit the crater while he was in the region. This was surely an opportunity Fairchild did not want to pass up.

With its awesome expanse of more than 4,000 feet across, and a depth of 570 feet, the Arizona crater impresses even the most jaded tourist today. One can imagine Fairchild’s exuberance and eagerness to learn what created this world wonder. By 1906 few people had seen the crater and even fewer had stayed to study it. Fairchild had only two days to examine the geology, but what he saw and heard from site manager Samuel J. Holsinger, convinced him the great depression had been created by impact.

The 10th International Geologic Congress (IGC) was held in September in Mexico City, shortly after Fairchild’s visit to the crater. As a delegate to the conference, Fairchild willingly brought the attention of the IGC attendees to the new findings. He took geologic samples along and passed out a dozen of Barringer’s paper which had been mailed to him in Mexico City. Renewed interest in the crater was certainly generated among the geologists due to Fairchild’s enthusiasm and stature as a professional colleague. By that time, at age 56, Fairchild had contributed at least forty articles to the geological literature and was serving as Secretary of the Geological Society of America (GSA).

Frequent correspondence with Holsinger, his host at the crater, ensued after his visit. Holsinger was given permission by Barringer to give Fairchild any photos or information he desired (Holsinger, 1906a). Until his death in 1911, Holsinger would send him specimens, update him on their drilling progress and exchange prints or lantern slides. They would engage in friendly discussions over the nature of the bolide and the impact, the samples and the contrary opinions of the "enemy forces" (D. M. Barringer’s term for the USGS scientists and others who opposed the meteoritic origin).

Barringer and his partner, Tilghman, were anxious to share their ideas with Fairchild since they had heard of his plans to read a paper about Coon Butte at the upcoming GSA meeting in New York. They wished to continue fostering his support but wanted assurance that his views aligned with theirs. He was invited to Philadelphia to meet with them. Apparently at this meeting Fairchild brought up the idea of a steam explosion created by heat generated by the impact. This "percussion cap theory" as Barringer called it, was not to his or Tilghman’s liking. Both men wrote long, detailed letters to Fairchild explaining why this idea was not compatible with mechanics or the geological facts. He was encouraged to consider carefully all that they had presented to him, before committing himself to a combination theory of meteoritic impact and steam explosion (Barringer, 1906c; Tilghman, 1906). Fairchild’s reaction was probable bemusement since he replied: "The energy with which you two men attack the fascinating problem is exceeded only by that of the projectile which made the hole. But I am sure that much more heat was generated by the impact than will be aroused by our correspondence" (Fairchild, 1906b). He feared that his suggestion for explosion (based on Upham’s original concept) was more "prominent and argumentative" than he felt. However, Fairchild defended his suggestion due to his concern that a buried meteorite might not be found (Fairchild, 1906a; Fairchild, 1906b). He recognized that to be prepared for such a possibility, an explanation for an explosion should be considered. It was a rational suggestion since a considerable number of holes had been drilled inside the crater and no definitive proof of a buried mass had been provided. Even Holsinger admitted to Fairchild, that based on their conversations and an article he’d read by Henry Ward on the Bath aerolite, he feared in his heart "that the meteor exploded and that all that remains of it is the wreck that is scattered over the plains." He realized this view was contrary to his commercial interests at the crater and were in conflict with his "great desire to possess the largest meteor in the world" (Holsinger, 1906d).

Origin of shale balls a clue to the nature of the bolide?

Among the intriguing features at the site were the plentiful magnetic iron "shale" fragments and "shale balls." Their appearance was different from the Canyon Diablo meteorite specimens that people had been collecting for years at the site. Shale balls occurred as fragments, curved flakes with a laminated structure, globular lumps, or were found encrusting irons. Their origin and relation to the CDs was a source of speculation. It was discovered that when those with iron centers were exposed to air, they disintegrated into iron oxide. The elemental composition of the iron shales was found to be similar to the Canyon Diablo specimens. Barringer believed the iron shales were produced by heat as the iron meteor passed through the atmosphere, and formed part of the luminous tail of the meteor. He described them as being like "flaming drops" which may have encountered and been smothered by the silica and rock being ejected from the just created hole (Hoyt, 1987, p. 92, 95).

Branner admitted to Barringer that being without expertise in mineralogy, he had no clue about the origin of the enigmatic iron shales. He reported that Oliver C. Farrington, meteorite expert at the Field Museum of Natural History, believed they were of meteoritic origin but didn’t think it mattered whether the lumps were "fused drops" or "fragments broken from the sides of a hot penetrating mass" (Branner, 1906). Farrington suggested the shale balls were simply irons oxidized by burial. George P. Merrill of the Smithsonian, on the other hand, said the sulphur-chlorine-rich individuals became oxidized upon exposure. To relate the two types of meteoritic irons found at the site he proposed a modification of Howell’s "plums in a pudding" hypothesis. The iron "plums" in an oxidizable "pudding" might have arrived as a heterogeneous mass of nickel-iron with segregated masses of easily weathered stony material (Hoyt, 1987, p. 122).

Holsinger sent Fairchild samples that he believed showed signs of fusion-cementation as related to the "flaming drops" hypothesis previously described. This was in response to Henry Ward raising the question of oxidation-cementation as an alternative explanation (Holsinger, 1906b). Fairchild was not satisfied that the samples showed fusion and Holsinger obliged by sending more. Holsinger told Barringer that Fairchild "...must put his hands in the nail prints. I think these specimens will convince the most doubting Thomas. But I think Prof. Fairchild is really convinced already but he wants absolute proof" (Holsinger, 1906c). However, upon inspection of these additional samples, Fairchild declared they did not prove fusion since they were hydrated to limonite. He believed that while "fusion products exist there, they are probably so changed by subsequent oxidation that it may not be proven" (Fairchild, 1906a). In addition he noted that it was unlikely the unchanged irons (Canyon Diablo siderites) had been kept dry at the surface while the changed specimens (iron shales) rusted due to burial. The nodular, laminated forms were "probably given that form by swelling and cracking due to absorption of O and H" he stated.

In December of 1906, Fairchild was ready to present a paper on the origin of Coon Butte to the GSA, that would reject the volcanic steam explosion hypothesis. Correspondence with the Standard Iron Co. men, analysis of specimens, and the study of geologic maps and photographs of the site had prepared him well for the presentation. Fairchild’s presentation may not have been completely to Barringer’s liking since he left open the question of the meteorite’s composition and its disposition. Fairchild wondered about the relation between the irons and the different types of iron shales. Did they represent two falls? Did they grade into each other, representing variations in composition or different hydration circumstances of one huge bolide? If the latter, Howell’s astral "plums in a pudding" idea might be relevant, even though extraterrestrial stony material had not been found at the site. Whether part of the wrecked bolide would still be found under the crater was an open question that only further drilling might answer (Fairchild, 1907).

Coon Butte is renamed by Fairchild

"I am going to make an effort to change the name of your dent in the earth" Fairchild revealed to Holsinger. "Is the raccoon found at all in Arizona? How did the place ever get such a silly name? Do you think of a better name than METEOR CRATER?" he asked (Fairchild, 1906a). Barringer had already agreed the new name, Meteor Crater, was more meaningful than Coon Butte or Coon Mountain (Barringer, 1906b). It was at the GSA meeting that Fairchild formally suggested a name change. The new name was quite well received since it had a nice ring to it and described its generic origin. Better yet, it agreed with the name of the nearest post office, Meteor, which Barringer had established not long before, at the Sunshine flag stop on the railroad. Although the name Meteor Crater became increasingly popular in use afterwards, the term Crater Mound was the official name from 1932 to 1946. This was due to the zealous efforts of Nelson H. Darton, a firm believer in the crater’s terrestrial origin. Since 1950, meteoriticists have recognized the scientific work of Barringer by referring to it as the Barringer Meteorite Crater. Although meteorite crater is technically more correct, Fairchild’s original name has stuck to this day.

Fairchild defends Barringer’s contributions

Fairchild’s early recognition of the impact theory along with other supportive scientists, helped focus the debate toward the nature of the bolide and its fate. Geological clues and calculations mounted over the years to support the idea of an explosive interaction between a bolide and the earth. Scientists with expertise in mechanics became involved in the debates. Fairchild made no direct contributions to these discussions for many years. The cessation of drilling between 1908 and the early 1920s, and in particular, the untimely death of Holsinger in 1911, coincide with Fairchild’s formal silence. Fairchild had infrequent contacts with Barringer during this time but delighted the latter with his continued interest in the crater (Barringer, 1915).

Fairchild was abruptly brought back into the crater saga more than once by the continuing trials and tribulations of Barringer and the Standard Iron Company. In 1926, Barringer had to convince the State of Pennsylvania that soliciting Pennsylvania stockholders into the enterprise in Arizona would not be misleading. He relied on supportive letters from his allies, including Fairchild, and eventually won the right to sell stock. Fairchild’s formal statement, to be used in court, verified that the crater was of impact origin and that "scientific men are no longer in doubt." He admits uncertainty as to "whether any of the meteor remains in the ground" but expressed hope that Barringer would have help in the search and overcome any opposition (Fairchild, 1926). The negative implication of his comments caused Barringer to realize he hadn’t informed the professor of their latest discoveries and sent him many pages of drill logs along with a paper he’d written (Barringer, 1926). It is unlikely that Fairchild’s opinions were changed by the reports of buried shale balls, drills stuck in meteoritic material, etc., having expressed doubts since 1906 about the existence of any significant quantity of meteorite remaining in the crater.

In 1928, Barringer sought Fairchild’s support one last time. An article by William Boutwell had appeared in the National Geographic Magazine that implied, by omission of information (i.e. Barringer and colleagues’ work at the crater), that G. K. Gilbert of the USGS had discovered the impact origin of the Arizona crater. Barringer was terribly upset by this insult. "I ask you to come to my rescue" he wrote to his long time supporter (Barringer, 1928). Fairchild responded by immediately writing to Gilbert Grosvenor, the editor, and then to John Edson, the chairman of the Board of Trustees, a few months later. His assertive letters clearly stated Barringer deserved credit for discovering the meteoritic origin of the crater (Fairchild, 1928a, 1928b).

Fairchild stated his belief that the late Gilbert knew he had made a mistake in concluding a steam origin and would, if he could speak now, say that Barringer deserved the credit for recognizing its meteoritic origin (Fairchild, 1928b). His assessment of Gilbert’s beliefs were based on the fact that Gilbert never spoke against the impact theory after Barringer’s and Fairchild’s papers had been published. In addition, Gilbert had privately given Branner, back in late 1906, the impression that this new information changed the conclusions he had drawn regarding the crater. Branner had shared this with Barringer and he in turn with Fairchild (Barringer, 1906a).

The incident with the National Geographic was symbolic of a problem that had been building for over two decades. Careful scientific endeavors by a significant group of geologists had validated the claim that the crater was of impact origin. Yet, something important was missing - official recognition of this work from the top geologic institution - the USGS. Support from geologists associated with the survey was either negative, non-committal, or only privately positive. The official silence of the USGS, to what seemed like incontrovertible evidence for impact, frustrated those who believed in this origin.

A flurry of correspondence from Barringer’s supporters brought few replies and no correction or retraction from the National Geographic Society’s board of trustees. Barringer was then encouraged to write a letter to Science which would be followed by an article from Fairchild. Fairchild knew that as a former long time friend of Gilbert, it would be appropriate for him to speak his mind (Fairchild, 1929a). Although the editor did not accept Barringer’s letter, he did publish Fairchild’s article in May, 1929 (Hoyt, p. 255). Fairchild questioned the scientific and journalistic ethics of the National Geographic by not crediting Barringer for his contributions to the crater studies, and attributing them to Gilbert and the USGS instead. He also criticized the attitude of the survey which had from 1893 by its silence, held to the steam explosion hypothesis by ignoring the work of other scientists since Gilbert. He ventured to suppose the chief reason for ignoring the truth was the fact that "an eminent and beloved member of the survey" had made a mistake. He further supposed that "confession by the survey will of course be painful." and that "...evidence of humility and admission of fallibility by a great bureau of the government would be something new." (Fairchild, 1929b). A statement from the National Geographic or the USGS never appeared. Their silence would not be broken until several more decades passed and government associated geologists would once more reappear to study Meteor Crater.

Explosion of bolide accepted

Fairchild’s condemnation of the two well known institutions marked a turning point in the Meteor Crater and impact cratering studies. Lack of support from the USGS was offset by the interest of certain astronomers and physicists who joined in the Meteor Crater studies. A quiet but intense debate concerning the size and velocity of the meteorite, and its dynamics in the atmosphere and lithosphere began (Hoyt, 1987, p. 264). Heated correspondence was exchanged between eminent physicists, geologists and astronomers. The calculations of astrophysicist Ray F. Moulton, addressed in several reports, gained repute and Barringer was shaken by them. Moulton confidently showed that a meteorite or a swarm of meteorites with a mass less than most presumed, struck at cosmic speed. The shock of impact pulverized and vaporized both strata and meteorites, which were violently thrown out. An incredible explosion had occurred after all. One of the debaters on the losing side facetiously agreed: "It’s a hell of a big hole and it was made by a hell of a big thing!" (Hoyt, p. 317).

It was in the midst of the debate that Barringer died, late in 1929. After writing a paper recognizing the work of Barringer, Fairchild prepared another article about Meteor Crater for publication (Fairchild, 1930). The fate of the bolide that created Meteor Crater was an interesting problem that he wanted to address. He submitted his manuscript to the Barringer sons and astrophysicist Moulton for comment. Because he emphasized the explosive fate of the bolide, the Barringers did not agree with Fairchild’s conclusions, while Moulton only questioned that the meteorite had been stony (Barringer, B., 1930; Barringer, D.M. Jr, 1930; Moulton, 1930)

Fairchild questioned whether the bolide could penetrate itself deeply under the southern wall as claimed by the Barringers (Fairchild, 1930). The Barringers on the other hand, couldn’t see evidence for a violent explosion (Barringer, B.,1930; Barringer, D. Jr., 1930). They also held that the bolide had been a swarm of irons, best described as a comet. The elder Barringer had first described it as such before the expected arrival of Halley’s comet. In this model the rounded iron nodules were explained as having been abraded in the cometary swarm, while the pits in the irregular Canyon Diablo irons were explained by oxidation. Fairchild claimed the latter irons were undecomposed segregations from vanished material - either stony or oxidizable iron. The nodules, he implied, were oxidized irons intimately associated with the irons, i.e. the irons were nuclei of shale balls. But the Barringers noted that known siderolites (stony-irons) contain only irregular inclusions, not rounded ones. The perishable nature of some meteorites was pointed out by Fairchild using an example of a typical Canyon Diablo that had disintegrated to powder in his university collection. Because of the perishable nature of meteorites and the significant outnumbering of stony falls to iron falls, Fairchild (1930) felt confident in proclaiming that time had erased most of its mass.

Moulton shared with Fairchild some results from his meteorite impact computations regarding kinetic energy, resistance at penetration, and the explosive results. "Your conclusion reached by a different train of reasoning are in a general way in harmony with my own" he agreed (Moulton, 1930). Fairchild kept Moulton’s figures in mind when he wrote about the affects of the meteor’s kinetic energy which resulted in shattering of the strata, the meteorite and the formation of intense heat. The fusion of the pulverized Coconino sandstone into a glassy material, and the nickel-iron stains from vaporization were proof of the latter. The saturated water in the porous sandstone must have expanded rapidly after initial compression. Therefore, Fairchild brought in steam explosion as a major factor in the expulsion of the rock. His earlier thoughts, once disparaged by Barringer and Tilghman, had once again resurfaced. The argument had ironically come full circle; the explosion as recognized by Gilbert so many years previously, but from the wrong cause, was once again being advocated.

The Planetesimal Theory captures the imagination of the Meteor Crater proponents

Modern concepts of solar system origin are based on several basic hypotheses advanced in the last two hundred years. Pierre Laplace’s nebular hypothesis has enjoyed popularity since 1796. In the 1880s, J. Norman Lockyer’s description of the origin and evolution of celestial bodies included collisions between swarms of meteoroids. At the turn of the century, another concept was explored by geologist T. C. Chamberlin, and astronomer, Forest R. Moulton. Their planetesimal hypothesis described the falling together (accretion) of the solar system bodies from matter that had been torn from the sun as it nearly collided with another star. The older nebular hypothesis proposed that the planets formed from superheated gases that first coalesced into liquids, then solids. It followed from this theory that as the earth cooled, it shrank, producing basins and mountains (Dawson, 1873, p. 7-14). The new planetesimal hypothesis on the other hand, described the planets as growing by cold accretion. Gilbert, as described earlier, had originally envisioned the Arizona crater being formed by a late arriving planetesimal and had later created the moonlet hypothesis based on a planetesimal concept.

Fairchild’s acceptance of the planetesimal hypothesis manifested itself first in finding explanations for earth processes, and much later, to explaining the lunar surface. Fairchild believed the cold accretion process, if true, demanded rethinking about certain earth processes. So he presented a paper at the GSA meeting in St. Louis in 1903 in which he discussed the possible changes in geological thought that would come about by accepting this hypothesis over the nebular concept. Fairchild’s anticipated publication of "Geology under the new hypothesis of earth-origin" met with disapproval from at least two of Chamberlin’s friends. Apparently Chamberlin had not published a detailed account of his view, so they felt this should come first. Claims were made that Chamberlin did not approve of Fairchild’s paper (Leverett, 1904; Russell, 1903). Fairchild had indeed received approval from Chamberlin, who stated the paper was a "...clear and effective statement and my only suggestions relate to minor points." He realized Fairchild had brought out some features and applications that differed from his own conceptions, but variations in view "are as inevitable as they are desirable," he said. He even appreciated Fairchild’s enthusiasm (Chamberlin, 1903).

Fairchild was embarrassed by all the uproar and reminded those in GSA withholding publication, that his paper was not a discussion of the hypothesis itself, but the hypothesis’ application to solving geologic problems. Only he was responsible for its contents, not Chamberlin (Fairchild, 1904). The paper was published that year in several journals and included a discussion by four other scientists.

Fairchild would once more publish in reference to the planetesimal hypothesis, but not until 1938. Suffering from vision loss, he nevertheless produced, at age 88, "Selenology and Cosmogeology; Cosmic and Geologic Import of the Lunar Features" (Fairchild, 1938). In this paper he made connections between the origin of the solar system, the lunar topography and Meteor Crater. He excused himself for "trespassing in the astronomic field" since geologists have "some reasonable ideas in selenology." He was referring to the contributions of geologist T.C. Chamberlin, who with Moulton, had supposedly overthrown the nebular hypothesis. Perhaps he also thought of, without mentioning, the earlier selenology contributions by his fellow geologist G.K. Gilbert, or even those of D. M. Barringer.

Gilbert’s lunar studies in 1893 as discussed previously, resulted in some unique insights but had no impact on the prevalent way of thinking. By 1912, Barringer too was convinced of lunar cratering by impact and in the ensuing years would draw analogies between lunar craters and Meteor Crater (Hoyt, 1987, p. 157). In the 1920s he wrote a few articles about lunar cratering, one of which he requested Fairchild to critique. His goal, he explained to Fairchild, was to stimulate an interest in lunar topography among geologists. He believed that too many geologists, not caring much about the moon, followed the lead of astronomers who had "made up their minds long ago that the craters, etc., on the moon are the result of volcanic activity." The planetesimal theory, he thought, was upheld by the validity of impact cratering. He was convinced that geologists who studied the moon well, would reach the same conclusion as he had (Barringer, 1925).

Fairchild’s 1938 article, was his last and 264th published paper (Tinkler, 1962). In it he continued to uphold the planetesimal theory of Chamberlin and Moulton, and used Meteor Crater as a terrestrial feature that could be compared with lunar craters. The article stated lunar craters were created by impact and were "ocular confirmation" that "planets were built by cold accretion" which "implies acceptance of the planetesimal hypothesis". He made the point that earth and moon studies had been retarded because of the adherence to a mistaken concept - Laplace’s nebular hypothesis. He espoused the idea that geology favors the cold accretion concept of the newer cosmology. In a letter to Moulton, before the paper’s publication, Fairchild with some humor wrote: "We must believe our earth was not in a hot, molten state, but in a cold, Moulton state!" (Fairchild, 1938a).

Moulton and Fairchild discussed what difference, if any, impacts on solid rock versus lose material might have. At that time it was assumed the moon was composed of unconsolidated materials. Fairchild had assumed an impact on solid rock, as happened in Arizona, would result in an explosion, while impact on the moon would result in the burial of a bolide. Further evidence for bolide burial was drawn from projectile experiments that showed resurgence of the missile created central peaks, as on the moon (Fairchild, 1938a, 1938b). But Moulton did not think the surface material would influence the impact nor the resulting explosion (Moulton, 1938). In his article, Fairchild did not concede on this point to Moulton, an expert in ballistics and explosion physics. He indicated that the planetesimals penetrated the "lunite" with a splash, and were heated and melted while being engulfed. Resurgence from the shock created central peaks and flat floors from semimolten material. Vaporization didn’t occur he declared, but fusion did, which explained the dark color resembling lava. The maria, he explained, resulted from subsidence on the moon which somehow erased previous cratered topography. By assuming the lunar lithosphere is so different from the Earth’s crust, Fairchild conveniently explained an unknown by claiming that "the peculiar mechanics are difficult of interpretation" (Fairchild, 1938).

Fairchild was surprised to discover that T.C. Chamberlin, co-author of the planetesimal hypothesis preferred the volcanic explanation for lunar topography. This was affirmed by correspondence with the late Chamberlin’s son Rollin (Fairchild, 1938c; Chamberlin, 1938). Contrary to Fairchild’s view, Chamberlin envisioned the maria as possibly being covered by lava. If true, this implied prodigious volcanic activity. The unequal distribution of lunar craters was further evidence of volcanic, rather than impact origin. Apparently, Chamberlin envisioned planetesimals accreting early in the history of the earth-moon system, not later, to produce the current topography. He believed meteorites today could be left over planetesimals or visitors from outside the solar system. Fairchild seems to have borrowed these words in his article to describe the errant meteoroid that created the Arizona impact crater, but ignored T. C. Chamberlin’s contrary ideas.

A penchant for accepting new ideas when they explained the facts better than the old ideas, enabled Fairchild to promote radical concepts, such as the planetesimal theory. The foundation of geological thought was shaken by this theory, but Fairchild accepted this as a new way to explain certain geological processes. His efforts would aid the difficult transition to a new paradigm. Many years later, at Fairchild’s memorial service, J. E. Hoffmeister (1946) would credit him, more than any other geologist, with "the successful readjustment of ideas to meet the requirements of the Planetesimal hypothesis."

Fairchild’s cosmogeology article made no new contributions to impact cratering studies but it served as an affirmation for an Earth-Moon model that he had promoted for many years. Chadwick (1945) described this last article by Fairchild as "the concentrated essence of his philosophic thinking in the great field of cosmic geology." Similar views to Fairchild’s and those in opposition would be debated for several decades more, until the dawn of the space age. Cosmic geology would then become an acceptable interdisciplinary subject of study - astrogeology. Appropriately, at the dawn of the manned space age, the first terrestrial training field site was at Meteor Crater. Once again the crater was recognized as a link between the Earth and the rest of the solar system.

 

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