After the L’Aigle shower of 1803, a whole new era opened in the study of meteorites. No longer did scientists hold these objects up to ridicule and scorn. Instead, they came to regard meteorites as well worth collection and careful study.
The Vienna Museum, the British Museum, the Paris Museum, the Academy of Science of St. Petersburg (now Leningrad), and the U.S. National Museum began to build up splendid meteorite collections. Scientists in Germany, England, France, and Russia engaged in the painstaking mineralogical study and classification of individual meteorite specimens.
The modern science of meteoritics is rooted deep in the nineteenth century. Many special fields of investigation had their beginnings then. Scientists became interested in the chemistry, the mineralogy, and the metallurgy of meteorites; in the orbits of meteorites and the trajectories they follow through the earth’s atmosphere down to impact with the ground; and in the distribution of meteorite falls in space and time.
From this period we can date such milestones of progress in meteoritics as:
The discovery of the beautiful and significant Widmanstätten patterns characteristic of the majority of the irons, and the less spectacular but equally important lines named for J. G. Neumann, the German meteoriticist who discovered them, in 1848, in the Braunau meteorite.The realization that there were many different kinds of meteoritesand that these diverse objects were very important to an understanding of the internal structure and origin of the earth, and perhaps of the Solar System and the wider cosmos as well.Tentative explanations of the violent and terrifying light and sound effects connected with meteorite falls.Tentative explanations of such oval-shaped areas as shown above.
The discovery of the beautiful and significant Widmanstätten patterns characteristic of the majority of the irons, and the less spectacular but equally important lines named for J. G. Neumann, the German meteoriticist who discovered them, in 1848, in the Braunau meteorite.
The realization that there were many different kinds of meteoritesand that these diverse objects were very important to an understanding of the internal structure and origin of the earth, and perhaps of the Solar System and the wider cosmos as well.
Tentative explanations of the violent and terrifying light and sound effects connected with meteorite falls.
Tentative explanations of such oval-shaped areas as shown above.
Typical distribution of meteorite fragments according to size, within oval-shaped area of fall. The larger masses of the shower carry farther on, in the direction of the motion of the meteorite. As early as 1814, investigators had noted this peculiarity of meteorite-shower distributions. See pp.32,89,94.
Typical distribution of meteorite fragments according to size, within oval-shaped area of fall. The larger masses of the shower carry farther on, in the direction of the motion of the meteorite. As early as 1814, investigators had noted this peculiarity of meteorite-shower distributions. See pp.32,89,94.
By 1850, A. Boisse, an early French geologist and meteoriticist, had put forth the basicmeteorite-planethypothesis. According to this theory of his, meteorites are the fragments of a planet[12]that formerly orbited between Mars and Jupiter in what is now called the “asteroid belt.” And untold millions of years ago, this planet was shattered by some unknown but very great force, possibly collision with another celestial body.
The structure of the meteorite-planet was considered to have been very much like that of the earth. The various divisions of recognized meteorites were believed to be representatives of the several concentric, or nested, shells of material originally making up the destroyed planet. These shells were progressively less dense with increasing distance from the center of the planet.
Today Boisse’s theory is one of the most widely accepted as an explanation of at least one major category of the meteorites. Some modern investigators would insist that the meteorite-planet had a thin outer glassy shell from which the tektites came.
Most of the larger fragments of the meteorite-planet, now called theasteroids, move so that the average asteroidal orbit very closely approximates the orbit of the original planet. But many of the smaller fragments follow paths in space that differ considerably from the original meteorite-planet’s orbit. Even some of the asteroids behave this way, either because of the high speeds they acquired at the time of disruption of the meteorite-planet, or because of the later influence of the major planets and particularly of the giant planet, Jupiter.
A diagram (not drawn to scale) showing position of asteroid-belt with respect to the orbits of Mars and Jupiter. The asteroids with average orbits move within this belt. The non-typical asteroid indicated follows an orbit that brings it well inside that of the earth. There are a number of asteroids with such peculiar orbits. It is possible that in the past a nickel-iron asteroid in one of these orbits collided with the earth and produced the Canyon Diablo meteorite crater.
A diagram (not drawn to scale) showing position of asteroid-belt with respect to the orbits of Mars and Jupiter. The asteroids with average orbits move within this belt. The non-typical asteroid indicated follows an orbit that brings it well inside that of the earth. There are a number of asteroids with such peculiar orbits. It is possible that in the past a nickel-iron asteroid in one of these orbits collided with the earth and produced the Canyon Diablo meteorite crater.
In fact, at the present time, several asteroids move well within the orbits of the earth and Venus. It is quite possible therefore that such a large meteorite crater as the one at Canyon Diablo, was produced by the prehistoric fall of one of these small members of our Solar System. If so, we have reason to believe that a core-fragment of the meteorite-planet came to earth at Canyon Diablo. For the extensive mining operations carried out there during the last half-century have shown that the projectile responsible for this greatest of all meteoritic shell-holes in the face of Mother Earth was a mass of solid nickel-iron, which in all likelihood was core material.
The lengthy and costly series of mining operations at Canyon Diablo were all undertaken in the hope of locating the “main mass” of this huge projectile and thus of opening up what might be called a cosmic-lode of quite valuable metals. Unfortunately, the miners overlooked the fact that impacts at meteoritic speeds produced almost incredible amounts of heat. Even the solid iron meteorites are vaporized and widely dispersed at the temperatures resulting from such impacts, as we have seen was the case at Wabar (seeChapter 4). So it was at Canyon Diablo.
The idea of a cosmic-metal mine might at first strike some readers as too futuristic to take seriously. But the necessity for catching a core-fragment before it enters the consuming atmosphere of our planet is really nothing new. As far back as 1939, the senior author had occasion to point out that if we wish to start a successful cosmic-metal mine, we must catch our core-fragment before it is turned into unminable vapor. This point will come up again in thenext chapter.
Cross-section of Boisse’s hypothetical meteorite-planet. Fragmentation of this sphere was believed to have given rise to the following divisions of meteorites:Theironmeteorites came fromA, the dense nickel-iron core.The stony-iron meteorites came fromB, the intermediate zone of cellular nickel-iron and silicate minerals.Thestonymeteorites came fromC, the outer zone of silicate minerals in which relatively little or no nickel-iron is present. The chondrites were believed to come from the inner portion of this zone; the achondrites, from the outer portion.
Cross-section of Boisse’s hypothetical meteorite-planet. Fragmentation of this sphere was believed to have given rise to the following divisions of meteorites:
Theironmeteorites came fromA, the dense nickel-iron core.
The stony-iron meteorites came fromB, the intermediate zone of cellular nickel-iron and silicate minerals.
Thestonymeteorites came fromC, the outer zone of silicate minerals in which relatively little or no nickel-iron is present. The chondrites were believed to come from the inner portion of this zone; the achondrites, from the outer portion.
There are several other theories of the origin of meteorites interesting enough to mention. The early view that the meteorites were debris thrown out by ancient volcanoes on the moon or recent ones on the earth came to be discredited largely on physical grounds. On the other hand, extremely violentprimordialvolcanoes on the earth (not the weak ones of historic times, like Aetna or Vesuvius) could have ejected material that in much later times fell, and continues to fall back on our globe. This theory has not been ruled out and it still receives support, for example, from some authorities in the U.S.S.R. These same Russian scientists take most seriously a suggestion that the meteorites (and comets as well) were thrown out by volcanoes believed to exist on the planet, Jupiter—a theory dating back almost a century to the English astronomer, R. A. Proctor.
Some scientists believe that meteorites represent the congealed remains of gaseous bolts of matter ejected by the sun. Others interpret them as fragments of comets that have been torn apart by passing too close to the sun, which is the most powerful gravitational center in the Solar System.
Chemists, geologists, astronomers, and physicists—as well as the meteoriticists themselves—are constantly working toward a solution of the problem of the meteorites. Where do these bodies come from? What can we learn from them about their age and origin and about the age and origin of our Solar System? Years may be required, but eventually the riddle of the meteorites will be solved by the patient, concerted efforts of men and women of science.
Collapsed mine buildings in the bottom of the Canyon Diablo meteorite crater. A shaft was put down here in one of several unsuccessful attempts to locate the main mass of the meteorite. See pp.44-52.
Collapsed mine buildings in the bottom of the Canyon Diablo meteorite crater. A shaft was put down here in one of several unsuccessful attempts to locate the main mass of the meteorite. See pp.44-52.
So far we have considered what might be called the “pure” rather than the “applied” side of the study of meteorites. The investigator in any pure science asks of a new discovery, “What does this tell me about the universe? How does it better help me to understand the laws of nature?” Of the same discovery, however, the worker in an applied science will ask, “What practical use can be made of this gain in knowledge? What can it be made to do for mankind in general?”
These questions reveal a decided difference in viewpoint, but this difference does not reflect unfavorably on either class of scientists. In fact, there is a great deal of truth in the saying “Today’s pure science is tomorrow’s applied.” Actually, ways and means of taking advantage of seemingly useless scientific discoveries are constantly being found. The most famous example of this principle is the development of the atomic bomb from the results of Einstein’s researches in the abstract field of relativity. Here the seemingly mystic formula E = mc² came to have far-reaching practical applications indeed!
Meteoritics has some exceedingly practical applications. Far from being completely “out of this world”—as the recovered meteorites themselves originally were—this science has been and can be made to serve mankind in a number of rather unexpected ways. Meteoritics, the onetime “stepchild of astronomy,” is currently being regarded with ever-increasing respectby scientists and engineers working in many different fields.
Consider, first of all, the stainless steels that are so widely used in modern industry, and even the fine satin-sheen stainless “silverware” that graces our dining tables. These have wisely been patterned after a natural alloy with lasting qualities of strength, tenacity, and resistance to corrosion. This natural alloy is the one making up the iron meteorites.
Its toughness and durability became well known wherever attempts were made to section these metallic meteorites. Specially designed and extra-powerful sawing equipment is required to slice meteoritic iron, and even with it, progress is painfully slow. So astounded were those who first tried to cut iron meteorites with ordinary metal saws that one of the earliest practical results was the development of battleship armor plate composed of a commercial alloy called “meteor steel,” which mimicked the composition of the iron meteorites.
Of course, a good deal of the difficulty of sectioning meteorites arises from the fact that those doing the cutting are trying hard not to waste valuable meteoritic material. Every precaution is taken to keep the amount of “sawdust” to a minimum, for such finely ground up and contaminated meteoritic material is of little scientific use. And, in addition, scientists must guard against heating meteorites to high temperatures because such heating destroys the delicate internal structure of the masses. If these two considerations (loss of material and overheating) were unimportant, even a large meteorite could easily be divided up by use of such high-powered oxyacetylene torches as are used to dissect huge obsolete battleships.
At the Institute of Meteoritics, a thin, water-cooled blade of soft iron is driven slowly back and forth by an electric motor. Carborundum grit in water suspension is fed evenly into the narrow cut over its entire length. This grit becomes imbedded in the lower edge of the soft iron blade, which then acts as a “many-toothed” metal saw. Several meteorites can be sectioned simultaneously by this multiblade saw. In the future, such newly developed methods as high-speed particle jet streams or ultrasonic devices may be used to section meteorites both rapidly and economically.
In the field of cosmic ray studies, particularly those concerned with the protection of space travelers from harmful radiation, meteoritics can be of help. The recovered meteorites have already come through those regions that would be crossed by even the farthest-ranging spaceships. Consequently, a great deal can be learned from the study of meteorites about the intensity of the cosmic radiation that the crews of such ships must face once they get outside the earth’s protective air-shield.
The first study of this type was made in May, 1948, at the Institute for Nuclear Studies of the University of Chicago (now the Enrico Fermi Institute). Scientists made radioactivity tests on samples of the Norton County meteorite donated for this purpose by the Institute of Meteoritics and air-expressed to Chicago because of the intense interest in the radioactivity question. In October, 1949, English investigators ran similar tests at the Londonderry Laboratory for Radiochemistry, Durham, England, on samples of the freshly fallen Beddgelert, North Wales, meteorite discussed on pp.69-70. The results of these two pioneer studies were negative because the “Model-T” instruments available in 1948 and 1949 were not sensitive enough to detect the relatively low radioactivities present.
The 6-blade meteorite gang-saw in the machine shop at the Institute of Meteoritics.
The 6-blade meteorite gang-saw in the machine shop at the Institute of Meteoritics.
In 1955, however, scientists at Purdue University, using more refined counters, studied small nuggets of nickel-iron, also from the Norton meteorite. This time, the results of the radioactivity tests were positive. The investigators detected tritium (an isotope of hydrogen produced by cosmic-ray bombardment) in the samples. Furthermore, theamountof this rare isotope present indicated that the intensity of cosmic radiation outside the earth’s atmosphere may be very much higher than had previously been thought possible. “Forewarned is forearmed,” and from the standpoint of future astronauts, this is as practical a result as one could wish for!
In the relatively near future, men will certainly land on the surface of the moon. We know from radiometric studies that some degree of radioactivity is induced in meteorites by the full-intensity cosmic radiation to which they have been exposed during their motion through space. The nearly airless moon, like the meteorites, has also been exposed to very intense cosmic radiation for a long time. So those who are planning to land on our satellite are concerned about the radioactivities they will encounter when they begin their explorations of the lunar surface.
Suppose that extra-sensitive instruments were designed to pick up and measure the radioactivities. Suppose further that these instruments were mounted in a space-probe put in an orbit circling closely about the moon. Plans for such a project arenow under way. What types and intensities of lunar radioactivities might such probe-mounted instruments record?
Until such a space-probe becomes available, earth-bound space-scientists are seeking at least a preliminary answer to this question. They are doing this by investigating the natural “probes” that have come to us from space—the meteorites.
Investigators have undertaken such studies very recently by employing a new radiometric method technically calledgamma-ray spectroscopy. Work of this sort has been and is being done at the Los Alamos, New Mexico, Scientific Laboratory on scores of meteorite and tektite specimens loaned to the Laboratory by the Institute of Meteoritics. Some of the individual meteorite specimens tested weighed as much as 37 pounds, and are probably the largest single extra-terrestrial masses yet tested for cosmic ray-induced radioactivities.
Let us turn now to another important application of meteoritics. Any body in motion through the air or in space has a “striking power” of sorts. For some objects, this striking power, which is technically known asballistic potential, is very weak, as in the case of silky milkweed-down drifting through the air. Hailstones have a good deal more striking power, as may have been painfully demonstrated on your own head. And, finally, such masses as falling meteorites (and especially those orbiting in space, unretarded by atmospheric resistance) have an extraordinarily formidable ballistic potential. This is because meteorites are not only tough and dense, as good projectiles must be, but are also moving at high velocities—particularly high if the meteorites come into the Solar System from interstellar space.
For this reason, the speeds of meteorites are very important to scientists responsible for rocket flights and for keeping satellites aloft over long periods of time. Clearly, these men must have as accurate information as possible on where and how fast meteoritic particles are moving, so as to chart the safest routes for spaceships, and to develop satisfactory means of protecting rockets and satellites against the effects of bombardment by the smaller meteorites. For these “small-fry” cosmic missiles are so numerous that many of them are sure to be encountered even in brief flights outside the earth’s atmosphere.
Such information might also prove valuable in the future to the crews of spaceships on long flights into deep space. Such men may face the life or death problem of taking successful “evasive action” against giant meteorites that will seem like flying hills and mountains.
A strong parallelism exists between a meteorite fall and the re-entry of a nose-cone or data-capsule into the atmosphere. To a considerable extent, the difficult problems connected with the latter are being attacked at present through careful studies of meteorites. From the air-sculptured shapes of meteorites, their crustal flow patterns, and the thicknesses and types of fusion crusts they show, scientists are learning a great deal about certain factors connected with the re-entry problem. These factors include rate of vaporization, effects of extreme temperatures, and types of sculpturing to be expected as a result of encountering the resisting molecules of the atmosphere.
Relationship between (A) the trajectory of a falling meteorite, and (B) the re-entry stage of a V-2 rocket. The solid lines indicate the similar portions of the two trajectories.A.A METEORITE FALLB.A V-2 RE-ENTRY
Relationship between (A) the trajectory of a falling meteorite, and (B) the re-entry stage of a V-2 rocket. The solid lines indicate the similar portions of the two trajectories.
One of the most obvious applications of meteoritics in the future will grow out of the well-known fact that our earthly resources of many strategic materials—especially metals like iron and nickel—are fast becoming exhausted. The population of the earth is increasing at a mad pace, and an end to metal-consuming wars is still not in sight. The need for such metals can only become more and more acute.
According to one of the currently favored explanations of the origin of the meteorites, the core-fragments of the parent meteorite-planet are solid masses of nickel-iron alloy—like the mass that blasted out the Canyon Diablo meteorite crater. If this meteorite-planet hypothesis finally wins general acceptance, the meteoriticist of the future is almost sure to be set the task of pin-pointing as exactly as possible the whereabouts in space and time of the most easily accessible cosmic nickel-iron lodes of this sort. Once he has given an answer, the space engineers will take over, and mining operations will be started on the unlimited sources of essential metals to be found in outer space.
Initially, no doubt, metal recoveries will be freighted back to earth in rocket-load lots. But as the need for iron and nickel increases on a metal-hungry earth, vast engineering projects may well be undertaken to “snare” the larger metal meteorites and equip them with rocket motors. This will be done so that by use of rocket power, the natural orbits of the meteorites can be changed into orbits bringing them back to earth. Unlike the natural, uncontrolled Canyon Diablo meteorite fall that vaporized what would have been a rich nickel-iron deposit, the rocket-controlled meteoritic “metal mines” will be eased down to earth all in one piece.
Reading of the possibility of sending out expeditions to find large iron meteorites in the depths of space may bring to your mind an image of the fearless mariners of old who sailed their stout ships over dangerous, often uncharted seas in search of the great whales. The rocket crews of day-after-tomorrow will no doubt be equally fearless and resourceful as they navigate the sea of space, intent on capturing the great “metal mines” of the future.
The experience gained in such space-mining ventures will then be carried over into expeditions to ensnare the larger stony-iron meteorites. These masses of iron and stone will offer less favorable mining possibilities, but they can be turned into rocket-propelled and guided de luxe space-cruisers. By this term, we do not mean that these natural space-ships will house all the luxuries of the ocean-liners advertised in the travel magazines. Rather, we see them as providing roomy, comfortable “underground” living quarters. Furthermore, their occupants will be adequately protected by great thicknesses of metal and rock from the injurious radiations of empty space, and the meteorites that make the term “empty space” something of a misnomer.
Initially, such worlds-in-miniature will be much sought after as laboratory sites where the more violent and dangerous of the many experimental tests which venturesome man will wish to conduct can be carried on without danger to the close-packed billions populating the then-crowded earth.
Later on, these meteorites-turned-into-space-ships may be used to explore the dangerous and faraway corners of the SolarSystem, since the very substance of each massive meteoritic rocket-body will serve as an adequate and handy source of fuel supply.
When men have learned to live on such “homes away from home,” it is quite possible that the larger of these modified meteorites, after their interiors have been opened up for occupancy by the inroads of the fuel-hungry rocket-motors, may be steered into neighborly orbits about old Mother Earth. Here, these “natural” satellites will assume the unexciting but necessary roles of the extra living quarters that by then will be so urgently needed to accommodate the mushrooming population of the world of the future.
People who live in these super-urban outliers of Mother Earth may take the same pride in their natural, if converted, homes as many former city dwellers now take in the old-fashioned sprawling farmhouses they have rebuilt and occupied. Perhaps one of your descendants will live in such a meteorite-orb, and occasionally point the finger of scorn at the more elegant but unpleasantly overcrowded artificial satellites preferred by those migrants from teeming earth who lack the true pioneering instinct. Who knows!
If you are especially interested in meteoritics, you already may have read some good books on general astronomy. There are many and most of them are not too advanced for the beginner. Unfortunately, these books devote but little space to meteoritics, the “Johnny-come-lately” of astronomy. Almost all of the writings on meteors and meteorites you will find largely profitable to read are in professional meteoritical publications. A selected list of such publications, containing much or at least a worthwhile amount of material you will now be able to understand, is given below. Your chief difficulty in using this list will be in finding some of the more important items in the holdings of your public library, unless it is a large and well-stocked one. Your librarian, however, may be able to help you get the item from some other library—perhaps from that of a nearby university or college.
MEBANE, A. D. “The Canadian Fireball Procession of 1913, February 9,”Meteoritics, Vol. 1, No. 4 (1956), pp. 405-421. Eyewitness accounts of the most famous fireball procession on record.
OLIVIER, C. P.Meteors, Williams and Wilkins, Baltimore, 1925. An exhaustive survey of work done by visual meteor-observers.
SCHIAPARELLI, G. V.Shooting Stars, a translation by C. C. Wylie and J. R. Naiden, published in theProceedings, Iowa Academy of Science, Vol. 50 (1943), pp. 48-153. A pioneer treatise, dated 1867, which is basic to later work in this field.
WHIPPLE, F. L. “Photographic Meteor Studies, I,”Proceedings, American Philosophical Society, Vol. 79, No. 4 (1938), pp. 499-548. Fundamental paper on the subject. Of the six meteors analyzed, five followed elliptical orbits and one, a strongly hyperbolic orbit.
FARRINGTON, O. C. “A Catalogue of the Meteorites of North America to January 1, 1909,”Memoirs, National Academy of Sciences, Vol. 13 (1915). Contains fascinating accounts of the phenomena connected with meteorite falls, interspersed with lengthy technical chemical and microscopic studies of meteorites.
FARRINGTON, O. C.Meteorites[published by the author], Chicago, 1915. The classic American work on meteorites. The first half of the book is popular; the last half is technical.
HEY, M. H. and PRIOR, G. T.Catalogue of Meteorites, William Clowes & Sons, London, 1953. An exhaustive catalog of all recognized and also, unfortunately, of many doubtful meteorite falls and finds, from the beginning of the historical record up to December 1952.
LAPAZ, LINCOLN. “The Achondritic Shower of February 18, 1948,”Publications, Astronomical Society of the Pacific, Vol. 61 (1949), pp. 63-73.
LAPAZ, LINCOLN. “The Effects of Meteorites upon the Earth,”Advances in Geophysics, Vol. 4, edited by H. E. Landsberg, Academic Press, New York, 1958, pp. 217-350. A monograph covering such topics as meteorite hits upon buildings and people, meteorite detectors, and the nature and age of meteorite craters.
LEONARD, F. C. “The Furnas County, Kansas, Achondritic Fall (1000,400),”Contributions, Meteoritical Society, Vol. 4 (1948), pp. 138-141. This paper and the eighth item, above, discuss the phenomena of the fall of the largest aerolite so far recovered anywhere in the world.
MERRILL, G. P. “The Story of Meteorites,”Minerals from Earth and Sky, Vol. 3, Part I, Smithsonian Scientific Series, 1929, pp. 1-163. A chiefly popular survey of the subject by a master meteoriticist.
PERRY, S. H.The Metallography of Meteoric[meteoritic]Iron, U. S. National Museum Bulletin No. 184 (1944). A summary of knowledge on the subject, supplemented by exceptionally fine photographs of etched meteorite sections.
SWINDEL, G. W., JR., and JONES, WALTER B. “The Sylacauga, Talladega County, Alabama, Aerolite: A Recent Meteoritic Fall that Injured a Human Being,”Meteoritics, Vol. 1, No. 2 (1954), pp. 125-132.
WHITE, C. S. and BENSON, OTIS O. (editors)Physics and Medicine of the Upper Atmosphere, University of New Mexico Press, Albuquerque, 1952. See Chapter X, “Meteoritic Phenomena and Meteorites,” by F. L. Whipple, pp. 137-170; and Chapter XIX, “Meteoroids, Meteorites, and Hyperbolic Meteoritic Velocities,” by Lincoln LaPaz, pp. 352-393. Modern views on the meteorite velocity controversy.
LAPAZ, LINCOLN. “The Craters on the Moon,”Scientific American, Vol. 181, No. 4 (1949), pp. 2-3. A popular exposition of the Bénard-Wasiutynski theory of the origin of the ordinary (nonrayed) craters on the moon.
SPENCER, L. J. “Meteorite Craters as Topographical Features on the Earth’s Surface,”Geographical Journal, Vol. 81 (1933), pp. 227-248. The classic paper on terrestrial meteorite craters.
BUDDHUE, J. D.Meteoritic Dust, The University of New Mexico Press, Albuquerque, 1950. An account of the various techniques used in collecting and studying meteoritic dust; and also of the conclusions drawn from the study of such dust.
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