COPYRIGHT, 1961, BY LINCOLN LaPAZ & JEAN LaPAZ
PRINTED IN THE U.S.A.

PREFACE

Meteoritics is the study of the only tangible entities that reach us from outer space. Except for the meteorites, scientists have to depend entirely on studies of some form of radiation for all their knowledge of the wider cosmos lying outside of the atmosphere of the earth. And none of the radiations reaching us from various sources afar can be held in the hand for examination. Each type of radiant energy incident upon our earth—whether that energy be light from the sun or from the more distant stars or the galaxies, or the reflected light from the planets and moons of our Solar System, or the less familiar forms of radiation, such as radio waves and cosmic rays—must be measured and permanently recorded by complicated instruments. Often the results given by even the most sensitive and tractable of these scientific robots turn out to be exceedingly difficult for man, their master, to interpret.

But the meteorites require no such temperamental instruments for their measurement. They are themselves a permanent record. They can be weighed, sectioned, and polished. They can be studied chemically, microscopically, and radiometrically. In fact, they can be investigated directly, just as they are themselves, in our hands, by any method modern science may be clever enough to devise.

This is why, now with the world’s attention drawn to ambitious plans for the exploration of the cosmos, meteors and meteorites are of increasing interest and importance.

We have planned and written this book to be a sound and yet largely nontechnical introduction to the science of meteoritics. Our daily experiences in the Institute of Meteoritics have afforded us a fortunate advantage in making such a presentation. For, in addition to our work in the field, laboratory, and classrooms, we have frequently conducted young people through the museum and workrooms of the Institute and so have had the opportunity of learning their point of view at the same time they were venturing into ours. We hope our book will instill in the reader an abiding interest in the location and protection, the recovery and preservation and especially in the study of those cosmic missiles of iron, iron-stone, or stony composition that represent mankind’s only ponderable links with the vast universe lying beyond the limits of the earth’s atmosphere.

Although all photographs and special depictions not made by our staff are individually credited, we wish to express our personal thanks for the privilege of reprinting them here. All photographs that are without a credit line have been made by members of our staff.

Lincoln LaPaz Jean LaPaz University of New Mexico, Albuquerque, March 20, 1961

TABLE OF CONTENTS

  PREFACE 5

1. A METEORITE FALLS IN THE TAIGA, U.S.S.R. 11

2. A METEORITE FALLS IN THE WHEATLAND, U.S.A. 23

3. FOUND AND LOST GIANTS 36

4. WHEN IS A CRATER A METEORITE CRATER? 42

5. HEAVEN KNOWS WHERE OR WHEN 66

6. FINDERS FOOLISH, FINDERS WISE 75

7. LANDMARKS, SKYMARKS, & DETECTORS 84

8. THE NATURE OF METEORS 101

9. THE NATURE OF METEORITES 118

10. TEKTITES, IMPACTITES, & “FOSSIL” METEORITES 134

11. OMENS AND FANTASIES 147

12. THE MODERN VIEW 158

13. PRESENT AND FUTURE APPLICATIONS 166

  FOR FURTHER READING 177

  INDEX 181

SPACE NOMADS
METEORITES IN SKY, FIELD, & LABORATORY

1. A METEORITE FALLS IN THE TAIGA, U.S.S.R.

The morning of February 12, 1947, dawned cold but bright and sunny in the wide Ussuri valley of Eastern Siberia. During the early morning hours the people in the villages went about their everyday chores as usual. Farmers fed and watered their livestock, while housewives tidied rooms and fired up stoves for heating and baking. Miners went to work deep underground. An artist seated himself outdoors near his home to make exercise sketches. In a densely wooded area on the slopes of a nearby mountain range, a logging crew began a day’s timber-cutting.

Suddenly, at 10:35 a.m., an extraordinarily large and brilliant fireball flashed above the central part of the mountain range. It streaked across the sky in less than 5 seconds and disappeared beyond the western foothills of the range. Then the inhabitants of a wide area heard what seemed to them a mighty thunderclap followed by a powerful roar like an artillery cannonade. Many people felt a strong airwave. (Field parties later found that those who noticed this effect were quite close to the place where the meteorite fell.)

For several hours afterward, a large black column of smoke tinged with a reddish-rose color stood above the place of fall. Gradually, this cloud spread outward, became curved and then zigzag in form, and finally vanished toward the end of the day.

The flash of the fireball and the loud noises that followed it caused panic among the farm animals. Cows lowed mournfully and herds of goats scattered in every direction, chickens and other fowl squawked in alarm, and dogs ran whining for shelter or crouched against the legs of their masters.

In the villages, the airwave blew snow off the roofs of houses and other buildings, while the strong earth-shocks opened windows and made doors swing ajar. Housewives were dismayed to see glass windowpanes shattered in their frames and burning coals and firebrands jolted out of the wood-burning stoves.

Even deep in the mineshaft, the vibrations in the air were strong enough to snuff out the miners’ lamps, leaving the men in darkness.

On seeing the huge fireball streak across the sky, the artist put aside his practice sketch and began a picture of the display before his impressions of it could fade. His painting of this natural event is now famous. Not only is it on display in scientific museums all around the world, but a color reproduction of it has been issued in Russia as a postage stamp.

The forester supervising the logging crew reported that his attention was first attracted to the sky when he noticed a strange “second” shadow rotating rapidly about the tree that cast it. On looking up, he saw a blindingly bright fireball, twice as large as the sun, a fiery globe that threw off multicolored sparks as it passed. Not long after the fireball disappeared behind the trees, the forester heard a loud noise like nearby cannonading and saw a large dark-colored cloud—later tinged with red—billow up over the impact point. (The members of the logging crew were among the very few persons actually abroad near the place of fall. It turned out that they were only about 9 miles from it.)

As soon as the many eyewitnesses of the fireball had recovered from their fright, the questions almost everyone asked were “What could it have been?” and “Where did it come down?” To answer the first question was not as difficult as to answer the second. Local scientists in Vladivostok and Khabarovsk, the nearest cities of some size, suspected from the first that a very large meteorite fall had occurred. But exactly where? All they could be certain of was that the impact point lay in the Ussuri taiga, a formidable wilderness.

The Sikhote-Alin mountains lie along the Siberian coast between the Sea of Japan and the Tatar Strait. The Ussuri taiga is a vast, low-lying, marshy, densely forested region fronting the western flanks of these mountains. Ordinary cedars, pines, oaks, and aspen grow in the taiga, but the region is also noted for such rare plants and trees as the celebrated ginseng, the cork tree, the Greek nut tree, and the black birch. Wild grape and ivy vines intertwine the upper branches of the thick forest, and the trunks of the trees themselves rise from an almost impenetrable maze of brush and downed timber.

So dense is the forest that in summer, a man can see no more than 10 or 12 feet in any direction. Yet in winter, the explorer’s lot is no easier; for, although the deciduous trees then stand leafless, the ground is covered by three feet or more of snow. And in the early fall, violent cloudbursts often flood the taiga, making travel impossible.

Such was the inhospitable region in which the Ussuri, or (as it is now known in the U.S.S.R.) Sikhote-Alin meteorite, had chanced to fall. For any search parties traveling on the ground, the likelihood that they could find the fallen meteorite in that wilderness would have been very small.

The impact point of the Ussuri meteorite was discovered in the only way really practical: from the air. Fortunately, the center of impact lay almost directly below the airlane connecting the towns of Iman and Ulunga, so that the devastation produced by the meteorite fall in the taiga was clearly visible to aviators following this active air route.

The accounts several fliers gave concerning the widespread cratering and destruction they had seen from the air in the impact area led to the organization of two separate ground-search parties, one at Khabarovsk, the other at Vladivostok. The Khabarovsk group, made up of four members of the Geological Society, flew to the village of Kharkovo, the inhabited point nearest the site of fall. After a rough and dangerous landing on the small, snow-covered airfield at Kharkovo, the geologists began their trek into the taiga on foot. Throughout the entire trip, the men, burdened with supplies and equipment, waded through waist-deep snow and camped in the open despite the arctic cold.

At almost the same time, a geologist from Vladivostok set out from the railway line up the Ussuri valley to track down the fallen meteorite. His progress was even more difficult than that of the Khabarovsk party. In addition to following a much longer route, he did not have the invaluable information that the first party had got from the aviators. He had to make his way slowly from village to village, questioning eyewitnesses as he went and gradually determining the probable end-point of the meteorite fall.

The route followed by the Vladivostok geologist lay through the heart of the trackless snow-covered taiga. Fortunately, he had with him two hunters who were well acquainted with the rigors of travel through the taiga and knew how to live off the land.

They slept in hunters’ huts or under overhanging trees, drank melted snow water, and ate fried quail. But they had not gone far when they found that their footwear was completely useless for a trek through the wet, snowy taiga, because their felt hiking boots quickly soaked up water and became very heavy. So they swathed their feet in warm dry grass over which they tied large pieces of untanned leather. After that, the walking was much easier. They were able to cover the ground so rapidly that they reached Kharkovo only a day after the Khabarovsk geologists had landed there at the small airfield.

At Kharkovo, the three feasted on pork, milk, and honey. Then loading a few provisions on a borrowed horse, they started out to overtake the Khabarovsk party. They made such good time that the two groups were able to join forces and to enter the impact area as one expedition, on February 24, 1947.

A scene of great desolation awaited them in the central region of the meteorite fall. Masses of crushed stone had been hurled hundreds of feet by the violent impact. Denuded, uprooted trees lay about—some cut in two as neatly as if by a saw. Large cedars had been splintered where they stood or had been torn up by the roots and thrown some scores of yards.

Most impressive of all, though, were the numerous meteorite craters ranging in size from small bowl-like features to a basin more than 28 yards across and over 6 yards deep—a depression large enough to hold a two-story house. The investigators recovered many fragments of the iron meteorite that had broken to pieces not far above the earth’s surface and had peppered the area of fall with high-speed meteoritic “shrapnel.”

With their meteorite recoveries and photographs of the cratered area, the members of this first expedition returned to their respective towns and began a campaign by letter and wire to interest the Moscow office of the Academy of Sciences of the U.S.S.R. in making a full-scale investigation of the Ussuri fall. The officials of the Academy decided at once to send a special scientific expedition to the site of the meteorite fall.

A member of this later and better-equipped expedition compared the Ussuri crater field to a bombed-out area. In fact, some of the meteorite specimens were fragments that closely resembled pieces of shattered shell-casing. The edges of these fragments were jagged and bent, and their surfaces, which often displayed a rainbow-colored sheen, were grooved and scarred by impact against the hard rock underlying the region in which the crater field had been formed. In rare instances, the investigators noted spiral twisting of the fragments, an indication of the unusually violent disruptive forces to which they had been subjected at impact.

The scientists found several instances in which fist-sized meteorite fragments had actually penetrated into or through standing tree trunks, either becoming imbedded in the wood or driving a hole right through the trunk.

Many whole individual meteorites also were recovered. These were almost always covered by a thin, smooth “glaze” known as fusion crust. This crust forms on the surface of a meteorite as it plunges rapidly through the air. The heat generated during its flight causes the outer “skin” of the meteorite to melt. Later, when the mass has cooled off, the thin coating of melted material hardens, forming a rind or crust.

By the beginning of 1951, the Russians had sent three more expeditions to the site of the Ussuri fall. Their scientists found, in all, 122 craters (the largest more than 80 feet in diameter) as well as numerous funnels resulting from the penetration of smaller meteorites into the earth. By means of both visual and instrumental searches, they also recovered 20,000 meteoritic fragments and individual meteorites. The smallest Ussuri specimens weighed no more than the thousandth part of a gram. (There are 453.59 grams in a pound.) Some of these tiny masses were found lying cupped in leaves. The largest individual meteorite recovered weighed about 3,839 pounds. Altogether, approximately 23 tons of meteoritic material from the Ussuri fall are now in the collection of the Meteorite Committee of the Academy of Sciences, Moscow, while another 47 tons are believed to still be buried in the Ussuri crater field.

The Russian scientists carefully mapped the locations of the individual craters, penetration funnels, and meteorite recoveries. They made geologic and magnetometric surveys of the crater field, took aerial photographs of the entire area of fall, and prepared a documentary motion-picture covering the activities of the various expeditions. The area of the crater field has been set aside by the Russian government as a sort of scientific preserve, and is being made into the equivalent of what is termed a National Monument in the U.S.A. Several of the typical craters are protected by overroofed shelters to preserve these features for generations yet to come.

2. A METEORITE FALLS IN THE WHEATLAND, U.S.A.

February 18, 1948, had been a pleasant day in northwestern Kansas and as the supper hour approached, the sky remained blue and cloudless. Shortly before 5:00 p.m., a few people were still out of doors. An eleven-year old girl was hanging up the last of the family wash on a high clothesline. In the late afternoon sunshine, a woman and her son were enjoying a walk around the back yard of their home on a large Kansas ranch. Outside his house, a ten-year old boy was playing basketball with friends. A veteran of World War II was loading fodder in a silo. In the feedlot of his ranch, a farmer was stacking hay. A filling station attendant was working outside at the pumps, grateful for a spell of milder winter weather.

Without warning, a large and very bright fireball streaked across the clear sky from southwest to northeast. Ominous-looking white smoke-clouds mushroomed up from points in the fireball’s path. Shortly after the fireball disappeared, loud explosions and rumbling sounds drove thousands of people out into the open. The whole astonishing luminous display was over in a few seconds, but the strange clouds and the frightening sounds that followed the fireball’s passage continued much longer.

Although startled by the brilliant fireball and the strange thundering noises, the young girl, whose face had been turned skyward as she hung up the clothes, noted very carefully where she had seen the fireball disappear behind the tallest building in her home town. (Her sighting was later of great value to field parties from the Institute of Meteoritics of the University of New Mexico.)

The woman and her son were amazed to see an angry, boiling white cloud tinged with red developing overhead in the blue sky and to hear strange whizzing noises in the air around them.

The boy playing basketball heard a peculiar whistling or hissing noise just as he was ready to shoot a basket and, on looking up, saw the ball of fire slanting earthward. (This boy’s report was of particular interest, since it related to an unusual type of “sound” that travels at the speed of light rather than at the velocity of ordinary soundwaves.)

As a cannonading louder than any the veteran had heard on the battlefields of Europe echoed over the rolling countryside, he went temporarily into a state of shock.

The farmer stacking hay heard several explosions, felt a violent air blast, and finally heard a solid object strike the ground “with a smack,” as he put it, “like a clod hitting the earth.” (Later, field searchers found that this man lived only about two and a half miles south of the point where the largest fragment of the meteorite fell.)

Shortly after the passage of the fireball, the filling station attendant felt the legs of his trousers flap as if he were standing in a high wind, although he was more than 11 miles distant from the actual path along which the fireball moved on its way to the earth.

As in the case of the Ussuri fall, which had occurred about a year earlier, farm animals, chickens, and dogs were terrified by the strange and noisy event. Cattle tried to run through a fence to escape the deafening racket. A fine pair of horses panicked and ran headlong into a narrow gully, the walls of which collapsed on them during their struggles. Chickens dashed for the henhouse, screeching and cackling all the way. A dog that feared lightning jumped behind a haystack and finally ran to his master in alarm.

Although the majority of the people did not see the fireball itself, they were driven out-of-doors by the violent concussions that followed its passage, and thus got out under the open sky in ample time to see several large, turbulent white clouds mushrooming far overhead. From these clouds, a thick powder or dust filtered down through the air and collected on the surfaces of stock ponds and water tanks.

Some people thought the peculiar clouds were similar to those produced by atom bomb explosions. Many suspected that a V-2 rocket had “run away” from the proving ground at White Sands, New Mexico. One man disagreed with the opinion of his friends that the military had been experimenting and declared that it was “the Lord who was experimenting!”

The February 18 meteorite fall caused great excitement throughout Kansas and Nebraska, and it was the chief topic of conversation for days among the residents of the many small farming communities along the western half of the Kansas-Nebraska state line.

The Ussuri fall was studied by Russian scientists exclusively, and we have of necessity given, in Chapter 1, a secondhand account of the fall and surveys the Russians made; but field parties from the Institute of Meteoritics conducted on-the-spot investigations of the Norton, Kansas fall. As we were members of several of these field parties, the story to follow is a firsthand report.

A little before 6:00 p.m. on February 18, word of the mysterious explosion centering near Norton, Kansas reached the Institute of Meteoritics, in Albuquerque, N. M., through the kind offices of Civil Air Patrol personnel. Since a number of early reports had described the incident as an airplane falling in flames, it was only natural that the Civil Air Patrol and similar groups would take an interest in the occurrence. At once, the staff of the Institute began to interview eyewitnesses of the event through Civil Air Patrol channels and by long distance telephone, telegram, and letter. Soon we had collected enough information to show clearly that a large meteorite fall had been responsible for the unusual light and sound effects that had startled the inhabitants of Kansas, Nebraska, and adjoining states.

By March 3, the Institute staff had made a first determination of the probable area of fall. The center of this oval-shaped, 8 by 4 mile area lay about 15 miles north-northwest of Norton, Kansas and nearly on the Kansas-Nebraska state line. The meteorite had fallen in a region of wheat fields, pasture lands, and widely scattered farm houses. The countryside there is open and gently rolling. The small creeks winding through shallow valleys are marked in spring and summer by narrow bands of low green trees and bushes. Many of the hillsides are covered with unplowed buffalo sod.

On March 24, a field party left the University of New Mexico to make a survey of this area. Unfortunately, Kansas blizzards can be as severe as any in Siberia, and although the scientists gathered many helpful reports from eyewitnesses of the fall, heavy snow and high winds seriously hampered the work. The information they collected, however, confirmed the accuracy of the Institute staff’s first determination of the probable area of fall.

Late in the spring, a farmer in this area found a “strange stone” on his land and held it for identification by the second Institute party. This strange stone—which smelled like sulfur and had metallic specks in it—was the first piece of the fallen meteorite to be recovered.

Scientists and farmers soon found many other fragments during systematic searches of the rolling farm and pasture lands. The fourteen-year-old boy who had been walking with his mother at the time of the fall discovered a 130-pound fragment of the meteorite in a pasture that had already been carefully searched by grown-up meteorite hunters! This find was one of the two largest fragments recovered from the entire fall. The landing place of this large piece was marked only by a small hole in the sod, but, on prodding into this hole, the boy struck something rather solid. He ran at once to tell the lady who owned the pastureland, and together they dug out the fine meteorite.

This discovery brought interest in finding meteorites to a fever pitch, and it was soon possible to look in almost any direction and see farmers, or their wives and children, walking slowly across the fields and looking for meteorites.

Finally, in August, two farmers cutting wheat in a field just a short distance north of the Kansas-Nebraska state line found a deep hole when their tractor almost fell into it. They investigated and discovered that a very large fragment of the meteorite had buried itself deep in the ground.

Scientists from the University of Nebraska and the Institute of Meteoritics carefully excavated this huge meteorite. They found that the mass had plunged more than 10 feet into the earth. Quite by chance, its lower surface had come to rest in the ashes of a long-buried primitive cooking site.

The excavated meteorite looked and felt like a huge stone. Actually, it was stony in nature, but of a texture so fragile that it had to be wrapped in tissue paper, then in burlap, and finally covered with a thick coating of plaster of Paris before it could be lifted out of the ground. Those in charge of the removal of the meteorite borrowed this procedure from the paleontologists, who use it in the removal of fossil tusks and bones that otherwise would crumble away.

After the great meteorite had been raised out of the excavation, it was taken by truck to the University of New Mexico, in Albuquerque. There it was put on display beside the smaller 130-pound fragment found in May. By careful measurements, scientists determined the weight of the main mass to be approximately 2,360 pounds—a record weight for stony meteorites.[1] This remarkable meteorite, known as the Furnas County, Nebraska, stone, is now a prized item in the collection of the Institute of Meteoritics.

As more and more finds were made in the area of fall, we accurately recorded their weights and mapped their locations. In this way, we could tell how the pieces of the meteorite had distributed themselves according to size and weight over the oval-shaped area. The smaller and lighter fragments were slowed down by air resistance and fell first, while the 2,360-pound mass carried on beyond them and came to earth at the farthest point along the direction of flight.

The staff of the Institute took many photographs of the meteorites that were found, of the impact funnel made by the largest mass, and of the excavation and removal of that giant stone. Some of these pictures were published in scientific journals, others in magazine and newspaper articles. A few of our best photographs are included in this chapter.

Although the light and sound effects that accompanied the Ussuri and Norton falls were similar, the meteorites recovered from them were not at all alike. The Ussuri specimens were masses of nickel-iron so malleable that on high-speed impact with hard rock they had held together and taken twisted and ragged shapes. But the Norton meteorites were very fragile stony masses, many of which went to pieces either in the air or when they struck the ground. Almost all of the recoveries made of this very rare type of stony meteorite were fragments, not whole specimens. They somewhat resembled pieces of a strange whitish mixture of chalk and crystalline limestone containing tiny specks and lumps of nickel-iron. Many specimens were covered wholly or in part by a shiny varnish-like fusion crust, varying in color from jet black through yellow to almost pure white.

The largest meteorite recovered from the Norton fall was the 2,360-pound mass that formed the deep impact funnel. The smallest Norton specimens, like their Ussuri counterparts, weighed no more than the thousandth part of a gram. Altogether, nearly a ton and a half of meteoritic material from the Norton fall was collected by the Institute. Other small fragments may remain undiscovered in the Kansas and Nebraska wheatlands, but, unfortunately, because of the soft and fragile nature of the material they are composed of, it is likely that they have now weathered away so completely that they are no longer recognizable as meteorites.

Our stories of the Ussuri and Norton meteorite falls show how hard scientists work themselves (and others!) to find meteorites. Therefore meteorites must be important. The two accounts given also make clear that investigators of meteorite falls are almost entirely dependent upon observations made by nonscientists.

Scientists investigating meteorite falls greatly appreciate the help given them by children and adults alike. Field parties are powerless without it, and we should like to encourage people of all ages to continue this type of valuable cooperation. In Chapter 7, we shall tell more about how the individual observer of a meteorite fall can make his report really count.

3. FOUND AND LOST GIANTS

All meteorites are important from the standpoint of science, but a few deserve special mention because of the human-interest stories connected with them.

First place among famous finds should no doubt go to the massive Cape York, Greenland, iron, the largest recovered meteorite actually to have been weighed. The Eskimos called this enormous object “Ahnighito,” which means “The Tent.” Robert E. Peary, the discoverer of the North Pole, brought it to New York City by ship in 1897. His party had great difficulty hoisting the 34-ton mass aboard. Later, when the ship had put to sea, she encountered a serious navigational hazard. To the amazement and alarm of the crew, the huge nickel-iron meteorite caused magnetic disturbances that severely affected the ship’s compass.

Another of the giant meteorites, the 14-ton Willamette, Oregon, iron, became the center of a long legal battle in the early 1900’s. The man who originally found the meteorite and recognized its true nature felt that because the iron was on the surface of the ground and not buried beneath it (as the ore of a metal would have been), there was no reason why he should not move the mass from the place of find to his own property, three-fourths of a mile away. He did this very laboriously by means of a log-timber car, a capstan with wire rope, and a small horse. On learning what the finder had done, the company that owned the land from which the meteorite had been removed put its attorneys on the job of recovering the “purloined” meteorite. The Oregon courts, bowing to decisions made in previous cases involving ownership of meteorites, brought in a verdict favoring the owners of the land. Although the finder of the Willamette meteorite lost the decision, he nevertheless won the distinction of being the only man to have successfully made off with a treasure weighing 14 tons!

The biggest meteorite of all, of course, is the one that “got away.” In 1916, a captain in the Mauritanian army was taken by a native guide, secretly and at night, to the site of a colossal iron meteorite located in the dunes of the Adrar desert, in the far western reaches of the vast Sahara. The officer described the mass as measuring 100 meters (over 300 feet) by 40 meters (over 120 feet), with the third dimension hidden by the sand dunes. According to him, the mass “... jutted up in the midst of sand dunes that were covered by a desert plant, the sba, and it had the form of a compact, unfissured parallelopiped. The visible portion of the surface was vertical, dominating in the manner of a cliff, the wind-blown sand that was scooped away from the base of the mass so that the summit overhung; and that portion exposed to eolian [wind] erosion was polished like a mirror.”

The captain, at the request of his uneasy guide, returned from his hurried excursion without taking notes or making a map. But he did bring back a small 10-pound fragment of iron which he had found lying on top of the giant mass. This small fragment later proved to be a genuine meteorite, and is the only known specimen of the famous Adrar mass. It is preserved at present in the Museum of Natural History at Paris.

What has been called a conspiracy of silence among the natives of the Adrar area and the inhospitable nature of the region itself have successfully preserved the secret of the location of the enormous metallic mass described by the captain. The native guide died, apparently of poison, and although many inhabitants of the region are no doubt familiar with the whereabouts of the mass (whatever it is!), those questioned have consistently denied knowledge of its very existence. All recent attempts, not only by military but even by scientific expeditions, to relocate the gigantic metallic mass have failed. The whole Adrar case remains an intriguing puzzle to be unraveled, it is hoped, by future generations of meteorite hunters.

Another “lost” meteorite is one composed of stone and iron. The Port Orford, Oregon, stony-iron (as it is now named) was originally found in 1859 by a U.S. geologist who was engaged in a survey of what were then the Oregon and Washington Territories. According to him, the mass was quite irregular in shape and “4 or 5 feet [of it] projected from the surface of the mountain,” while it was “about the same number of feet in width and perhaps 3 or 4 feet in thickness.” He broke off a small fragment of it (far smaller than the one taken from Adrar) and packed this specimen away with his collection of rock and mineral samples. Years later, the geological collection was cataloged and analyzed in the East. At that time, the fragment collected in 1859 was found to be a piece of a stony-iron meteorite. After that, scientists and others made many attempts to rediscover the main mass of the large Port Orford meteorite, all of them unsuccessful. Today the sum total of material recovered from this stony-iron amounts to 25 grams in the U.S. National Museum, about 4 grams in the Natural History Museum of Vienna, and a few tiny specks in the Museum of the Geological Survey of India.

The Red River, Texas, iron is still another famous meteorite. It was originally discovered by Pawnee and Hietan Indians, and a group of them took a party of traders, in 1808, to the site. Two years later, two rival parties, each led by a man who had been a member of the 1808 trading expedition, began a search for the meteorite. The members of one of the two parties were from Nacogodoches, Texas. They reached the meteorite first but had left home so hurriedly on their eager hunt that they were not properly prepared to move so large a mass. They went away from the site to get horses and a wagon, after they had laboriously hidden the meteorite under a huge flat stone, to prevent the other party from finding it. The members of the other party, hailing from Natchitoches, Louisiana, set out better prepared. After a lengthy hunt, they finally found the hidden meteorite. Using tools they had the foresight to bring, they built a truck wagon and drove away with their prize. Eventually, the Red River meteorite, weighing 1,635 pounds, became a part of the collection at Yale University. But two other, smaller, masses of the same metal, known in the early days to the Pawnees and a few traders, remain still undiscovered in the Red River area.

4. WHEN IS A CRATER A METEORITE CRATER?

Not all meteorites form craters at impact, as the larger Ussuri fragments did. Even the largest mass of the Norton meteorite merely buried itself in a funnel-like hole only about 10 feet deep. And the Russian investigators found a number of the lighter Ussuri fragments at the bottom of small penetration funnels. Cosmic missiles that are large enough to blast out craters in the ground are of particular interest to science, however, not only because of the extraordinarily intense light, sound, and other effects that accompany their fall, but also because they produce characteristic and long-lasting basin-like features in the outer shell of the earth.

Natural processes that change the surface features of the earth have long been the subjects of field studies by scientists. Geologists have carefully investigated the major folds formed in the earth’s crust by mountain-building forces, the clefts and depressions resulting from earthquake activity and erosion, and the vast plains leveled off by the scouring action of great ice-sheets. All of these different natural processes, though, have one thing in common: their source is the earth-body itself. They take place either within the earth’s crust as a result of local shifts or changes in pressure (like earthquakes and volcanic eruptions), or on the surface of the earth as a result of the action of water or of changes in temperature (like erosion and glaciation).

On the other hand, meteorite impact craters are not formed by earth-processes at all. As we have seen, they result when large bodies of matter from the regions of space outside the earth chance to strike the surface of our planet at high speed. The study of meteorite craters is therefore a special field. It is also one of quite recent development; not until 1905 was the first meteorite crater recognized as such.

The first thing to be said on this subject is, of course, that not all holes in the ground, however large and impressive, were necessarily formed by the impact of meteorites. Features that resemble meteorite craters may result from certain ordinary earth-processes. For example, the rock layers underlying a particular area may be dissolved away by waters circulating beneath the surface of the ground. The overlying crust will eventually collapse into the empty space, and what geologists call a “sink hole” or a “sink” is formed. Many such sinks surround the genuine meteorite crater near Odessa, Texas, and at times have been mistaken for the real thing.

Since there is some possibility of confusion about whether or not a hole in the ground is a meteorite crater, it is comforting to know that scientists have come up with a handy set of rules for reaching a decision on this point. These rules can be stated in the form of several questions that crater-investigators should ask themselves:

Have you found meteorites in or near the crater-like feature?

In its vicinity, have you found pieces of country rock that show the effects of high temperature and pressure (melting or crushing)?

Did people actually see a meteorite come to earth at the point where the crater is located and where, to their certain knowledge, no crater existed before?

If the answer to all—or even one—of these questions is yes, then it is quite likely that the crater-like feature is actually a meteorite crater. Naturally, if the answer to the first question is yes, the matter is practically settled in favor of the meteoritic origin of the feature.

If the impact has taken place in horizontally bedded rock strata—that is, in flat beds of rock lying one on top of another like the layers in a stack of griddle cakes—a meteorite crater will have a characteristic rim of upturned or even overturned rock layers. (None of the ordinary sink holes near the Odessa crater show such rims.) In addition, pieces of rock shattered and thrown out by the impact will be found in all directions around the crater. The amount and size of this fragmented material will decrease with distance outward from the crater.

A list of the recognized (or genuine) meteorite craters of the world is given in the table on page 65. All of these craters except the two Russian ones were formed many thousands of years ago, and, in most cases, the earth processes of erosion and weathering have by now dimmed the sharp outlines of their rims and silted up their deep interior funnels until only basin-like bowls remain.