Chondrites and Chondrules

THIN SECTION OF CHONDRITE viewed through the microscope moved from their matrix in a chondrite. The sections were photo. (top) is interspersed with chondrules (colored bodies). The photo· graphed through polarizing filters, which here give the chondrules micrograph at bottom shows round chondrules that have been reo their color. Chondrules range from size of a pinhead to that of a pea.

The first are stony m�eteorites; the second, the small spherical bodies they contain. There is evidence that the chondrules date back to the opening stages in the evolution of the solar system

by John A. Wood

n 1802 an English chemist named bodies occurring in chondrites soon came similar to those of the solar atmosphere. Edward C. Howard cautiously titled to be called chondrules. In 1930 the German spectroscopists I a paper he had written "Observa From the beginning investigators Ida and Walter Noddack pointed out tions on certain stony and metallic Sub have tended to believe that chondrites additional evidence. They found that stances, which at different Times are said are pieces of planetary matter in a very chondrites contain a more generous as to have fallen on the Earth." Howard primitive state. If this matter is not still sortment of trace elements in measur seems to have been the first person to in exactly the form it took when the able amounts than any type of earth examine carefully the internal structure planets first coalesced, it is not many rock does. In particular chondrites con of stony meteorites, and in all four speci evolutionary steps removed from that tain, mingled together, lithophile, chal mens he studied (stones from England, form. Recent studies of chondrites and cophile and siderophile elements-ele Italy, Bohemia and India) he found chondrules provide reinforcement for ments that respectively tend to associate "abundant small bodies, some perfectly this concept and tell a story about the with silicate and oxide material, sulfide globular, others rather elongated or early history of the solar system. material and metallic iron material. If elliptical." Their size ranged from that the chondrites had been melted in the of a pinhead to that of a small pea, and The Antiquity of Chondrites parent meteorite planet, or if any kind their color from gray to brownish. of extensive material transfer had oc At that time the idea that meteorites At first the belief that chondrites are curred, the lithophile, chalcophile and were of extraterrestrial origin enjoyed primitive planetary matter stemmed siderophile elements would have tended roughly the same reputation flying largely from the mystique that is natu to segregate themselves as they have in saucers do today. In 1803, however, the rally excited by material from inter the earth. French village of L'Aigle was pelted by planetary space. In 1929, however, the Finally, isotopic-dating techniques de a shower of falling stones so dense first quantitative evidence appeared. At veloped during the past decade have (more than 2,000 were recovered) that that time the astrophysicist Henry Nor shown that although chondrites are very the Academie des Sciences was moved ris Russell, working at the Mount Wilson old-older than any earth rock studied, to appoint a commission, headed by the Observatory, used solar spectrograms to their ages clustering around 4.6 billion eminent physicist Jean Baptiste Biot, to make the first crude estimate of the rela years-they have been cold, inert bodies investigate the event. Biot's detailed re tive abundances of the elements in the most of this time. Some chondrites have port eliminated the possibility that the sun's atmosphere. He found that the recently been found to contain excessive stones were a hoax or a terrestrial abundance pattern for metallic elements amounts of the rare isotope xenon 129 phenomenon. Soon the idea that meteor matched the abundances in chondrites [see "The Age of the Elements in the So ites are fragments of another planet or fairly well. Later and more precise work IaI' System," by John H. Reynolds; S CI planets, probably broken up by mutual on the composition of the solar atmos ENTIFIC AMERICAN, November, 1960]. collisions, won wide acceptance. phere showed the match to be quite Xenon 129 is produced by the decay of After Biot's report museums began to striking [see illustration on page 75]. Ap iodine 129, an isotope with a half life collect meteorites enthusiastically. By parently both sun and chondrites were that is brief by cosmic standards: 16.4 1864 almost 200 meteorites had been made from the same parent material, million years. Those chondrites with studied, and it was evident that the great and the metal content of both has re excess xenon 129 must have cooled to a ma jority of meteorite falls were stones mained unchanged since. If melting low temperature while they still con containing Howard's "small bodies." In or some other form of material trans tained some iodine 129, and they must that year a classification of meteorites fer had occurred in the chondrites, it have remained cold ever since, because was set up by Gustav Rose, a German would have segregated the elements and heat would have driven xenon 129 out mineralogist; he named this majority introduced large-scale heterogeneities of the meteorite as fast as it was created class of meteorites "chondrites" after in metal abundances from one chon by iodine-129 decay. We conclude that their peculiar internal structure. (Choll drite to another. We know such frac the time interval between the creation dl'oS was the ancient Greek word for tionation occurs in the earth. No type of the iodine 129 and finalcooling of "grain of seed.") The small, rounded of earth rock has metal abundances some chondrites was short-less than

© 1963 SCIENTIFIC AMERICAN, INC BIRTHPLACE OF STARS is probably in dense clouds of gas and at bottom the nebula NGC 6611 in Scutum Sobieski. Light of neb· dust sucb as these nebulae, which contain stars regarded as young. ulae is emitted by atoms excited by radiation of nearby stars. Photo· At top is the Horsehead Nebula, part of the Great Nebula in Orion, graphs were made with 200·inch telescope on Palomar Mountain.

© 1963 SCIENTIFIC AMERICAN, INC ' 100 million years. Therefore high-tem eralogy. All gradations between these " ... , . . perature evolutionary events could have conditions were observed among the . . .. '. : . - . . : : . occurred only during the first2 per cent chondrites. We know that when rocks ' ,. ,' . ' . . , " ...... o. : . . : . . . or less of the lifetime of these chondrites. or metals are held for months or years . . . Chondrites fit rather well into the idea at high temperatures (but not melted), ' . . . . ." astronomers currently have of the nature the textures they had at first are often . ' of primitive planetary matter. For many replaced by systems of new, coarser

. . ,., years it was supposed that each planet c rystals. This recrystallization, or meta " . condensed directly from a discrete mass morphism, to use a geological term, oc ' -: .' . of hot gas that had been torn from the curs entirely in the solid state. Petrog sun (the J eans-Jeffreys hypothesis) . This raphers concluded that all chondrites

.' ...... concept was discredited, however, by a once had clear-cut chondrules but that . ' . .. theoretical study showing that hot gas many, like the stone from Milena shown . : would not remain in discrete masses long in the top illustration on the next page, enough to allow condensation. The view have been recrystallized by heat. Pre now held by most astronomers is that sumably they were heated in the interior any condensation that occurred yielded of their parent planet or planets. a large number of small granules, or The second inference concerns the "planetesimals," and that later these par chondrules themselves. Some were found ticles were brought together to form to contain glass, evidence that they had the planets. According to this picture been melted and then rapidly chilled.

' . ' planetary matter was at first a conglom Glassy chondrules occur only in relative , ' . , . . eration of planetesimals. Can it be that ly unrecrystallized chondrites, so that the . chondrules were the planetesimals? melting cannot be associated with the Studies of the intrinsic properties of metamorphic heating just described. chondrules and chondrites have given The presence of glass, the anhydrous or us part of the information needed to an high-temperature character of chondrule swer this question. minerals, the igneous texture of some chondrules and their spheroidal shapes Chondrites under the Microscope all these distinctive features of the chon drules pointed to the conclusion that Much of this information has come they had once been dispersed droplets from the study of meteorites with micro of hot molten silicate: a "fiery rain," in scopes, a study begun by Rose and his the words of the 19th-century English contemporaries. The internal micro microscopist Henry Clifton Sorby. Some structure and mineralogy of a rock can or all of the droplets had cooled rapidly -best be disclosed by making a thin sec on a time scale of minutes or even sec tion of it. A slice of the rock is cemented onds.

to a glass slide and carefully ground . ',' down to the thinness of a sheet of paper. The Formation of Chondrules Silicate minerals ground this thin are

. quite transparent, so that a fragment Many investigators have speculated = prepared in this way can be viewed on the origin of these hot droplets. Most through a microscope. Thin-section have concluded that the droplets were studies established that the chondrules created on or in parent meteorite planets are unlike any structures occurring in and that truly primitive planetary matter terrestrial rocks but that they are com did not contain chondrules. They thought posed mostly of olivine and pyroxenes, chondrules might be lava droplets that iron-magnesium silicate minerals com were ejected from volcanoes on the mon in the earth. They also contain small planets, or the molten debris of high amounts of feldspar, iron sulfide and velocity collisions between planets. sometimes nickel-iron metal, a natural A few workers have suggested, how "alloy" peculiar to meteorites. Moreover, ever, that chondrules were actually the microscopic observations allowed two first solid particles in the solar system inferences to be drawn about the history and that these subsequently accreted to of chondrites. form the inner planets, including the First, it was noted that chondrules earth. Naturally, no traces of chondri tic BIRTH OF SOLAR SYSTEM, according to are much more conspicuous in some character would be preserved on the current views, is depicted schematically in four steps. Vast cloud of interstellar gas and chondrites than in others. In a few the earth today. Complex evolutionary proc dust (top), spinning from galactic rotation, chondrules are quite sharply defined esses-weathering, sedimentation, melt had change of density causing start of col· and occur embedded in an opaque black ing-have reworked the earth's crust lapse from self-gravitation (2) _ As cloud matrix. In others the chondrules are time after time. neared size of present solar system, intensi scarce and hard to distinguish from their Strong evidence has recently come to fying spin had made it a disk-shaped nebula surroundings, the entire chondrite being hand that this latter hypothesis is prob (3) with dense mass, a proto sun, at center_ nearly uniform in granularity and min- ably true. Craig M. Merrihue and Robert The sun and planets then evolved (4)_

© 1963 SCIENTIFIC AMERICAN, INC CONSPICUOUSNESS OF CHONDRULES varies among chon distinct. At right is similar view of chondrite that fell at Milena in drites_ At left is microscopic view of a thin section of achondrite Yugoslavia. It has undergone recrystallization, probably from pro that fell at Tieschitz in Czechoslovakia; its round chondrules are longed heating in parent planet; the chondrules are indistin.·t.

O. Pepin, graduate students working 126 can only have been made in the flux of high-energv protons and alpha with John H. Reynolds at the Univer proportions observed by the reaction of particles similar to the solar flareswe sity of California at Berkeley, have high-energy protons or alpha particles observe today. If the chondrules had not separated chondrules from chondrites, (helium nuclei) with certain trace ele been dispersed, most of them would extracted the xenon from them and ments in the chondrules, particularly have been shielded from the bombard measured its mass spectrum. In chon tellurium and barium. ment by overlying pl anetary material, drules from the chondrite that fell at Present-day cosmic radiation is not inasmuch as high-energy protons can Bruderheim in the Canadian province nearly intense enough to produce the rarely penetrate more than one meter of Alberta they found the isotopes xenon effect. There is only one obvious way of ruck, and alpha particles are stopped 124 and xenon 126 to be more abundant in which the chondrules might have been by one millimeter. than they are in terrestrial xenon by as exposed to particle bombardment: they There is also evidence of a chemical much as a factor of three. As far as we were dispersed in space at a time when nature that chondrules were the original know this surplus xenon 124 and xenon the sun or protosun was emitting a dense solid particles in the solar sy"tem. It is

SEPARATED CHOND,RULES show the sp'heroidal shape of these both objects comes from chondros, the ancient Greek word for small hodies that characterize chondrite structure. Tbe name of "grain of seed." Lar·gest chondrules yet found are size of a pea.

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© 1963 SCIENTIFIC AMERICAN, INC believed that the solar system condensed ment and a beam of electrons, acceler from hydrogen-rich gases, almost the ated to about 25,000 electron volts, is same in composition as the sun is now. made to impinge on it. The beam is Thermodynamic calculations show that focused in a spot a few microns in diam the hydrogen in such a gas would reduce eter on the specimen surface. The speci iron oxide, that is, it would react with men acts like the target in an X-ray tube; POSTDOCTORAL the oxide, removing oxygen and leaving X radiation characteristic of all the vari iron metal. (In the reducing atmosphere ous elements present immediately under FEllOWSHIPS of a blast furnace, for example, carbon the bombarded spot is generated. Analy AT THE takes up the oxygen from iron oxide to sis of the X-ray spectrum yields the free the iron.) If the chondrules were elemental composition of that small vol WEIZMANN INSTITUTE OF SCIENCE once hot molten droplets in the cloud, ume. By such means it has been shown REHOVOTH, ISRAEL any iron oxide they contained would that the Renazzo chondrules contain ACADEMIC YEAR 1964-65 have been reduced. We might expect to abundant nickel-iron metal but little iron find iron metal in them after they had oxide: only .5 to 2 per cent by weight. cooled, but they should be almost devoid The chondrules in recrystallized chon A number of postdoctoral fellowships are of oxidized iron. drites, however, contain substantial available to candidates from any country for When we analyze the chondrules in amounts of oxidized iron, up to 16 per research in the natural sciences at the unrecrystallized chondri tes, such as cent. How can this iron be accounted Weizmann Institute of Science. They are those found at Renazzo in Italy or at for if the chondrules once existed under normally of 12 months' duration (including Tieschitz in Czechoslovakia, we find reducing conditions? The question is a one month of vacation); in special cases a that this is precisely the case. The ele fairly crucial one. Perhaps the chon shorter period may be approved. mental content of structures as small as drules after all were never associated The Weizmann Institute engages in funda· chondrules can be measured by optical, with the solar nebula or any other en mental research in Applied Mathematics, X-ray or arc spectrographic techniques. vironment that would prevent them from Biology, Chemistry and Physics. Research The recently developed electron-probe containing abundant oxidized iron. Per facilities are available in the following areas: microanalyzer offersa particularly ef haps they have contained oxidized iron fective means of measurement. A pol from the time they were formed, and the Applied Mathematics ished surface of the specimen is placed comparatively few chondrites containing Biochemistry in the vacuum chamber of the instru- reduced chondrules, like the Renazzo Biodynamics Biophysics Cell Biology Chemical Immunology Electronics Experimental Biology Genetics Infrared Spectroscopy Isotope Research Nuclear Physics Organic Chemistry Photochemistry Plant Genetics Polymer Research Theoretical Chemical Physics X·Ray Crystallography

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GLASSY CHONDRULES such as that shown here are evidence that chondrules were once molten hodies that cooled rapidly, since glass can only be formed in this manner. The fern· like, microcrystalline structures visible are characteristically found in quenched glasses.

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FORMATION OF CHONDRULES may haye occurred when a sion and "ooling, tinv liquid droplets re('ondensed (C) in metal shock wave passed through the soJar nehula, as shown in this dia· rich regions and then many of them coalesced through collision granl. Intensity of color reflects gas density at varioll� �tage:3 of the (D), forming chondrules_ After more cooling chondrules he came process. As wave passed, dust gathered hetween turhulent eddies solid (F). Meanwhile in metal-poor regions (E) prodUl"t of re,'on (A) was vaporized (8) hy compressional heating. On d"t:ompres- densation was dust grains; they and ehondrules accreted as planets_

and Tiescbitz stones, were the product of recrvstallization? It is possible; the iron dized iron would "want" to move from complex and atvpical circumstances. would not have to move very far. In un the magnetite into the chondrules; mag It turns out that the iron-oxide con reclTstailized chondrites such as those netite is thermodynamically unstable in tent of chondrules correlates strongly of Renazzo and Tieschitz the fine-grained a rock of chondritic composition, and the with the degree of recrystallization ob black matrix material between the chon chondrules contain olivine and pyrox served in the chondrules in which they drules contains abundant oxidized iron enes-stable minerals that can accept occur. Conlc1 the oxidized iron have been in the [onn of the mineral magnetite. \Ve oxidized iron in their crystal lattices. introduced into the chondrules during know that in such a situation the oxi- Oxidized iron would have been free to

w cr: ::J U) U) w 1: :::::::: ::::-' cr: �;.: .", · ·7· <---·+- ·····_-_ ·····..:--····_-_······_..;..·······_-_··---4 0.. . 1 _·- U) : :>

1,200 1,400 1,600 1,800 2,000 1,200 1,400 1,600 1,800 2,000 TEMPERATURE (DEGREES CENTI,GRADE)

PRESSURE AND TEMPERATURE REQUIRED for liquid drop dotted area, iron-metal liquids in colored-hal' area and solid iron lets and solid particles to exist in the solar nehula are shown in in area of colored dots. In hlank region only vapors are slable_ Dia these diagranls. At left gas is assumed to be same as sun's; silicate gram at right assumes enri,'hment of metal vapors in gas hy factor liquids can exist in gray-striped region and silicate solids in gray- of 100; liquids could exist at correspondingly lower pressures.

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© 1963 SCIENTIFIC AMERICAN, INC make this move when the thermal re ratio of nickel to iron, however, is essen crystallization of most chondrites oc tially the same for all the subclasses; the curred; high temperatures render atoms process that fractionated iron also frac mobile, able to diffuse through crystal tionated nickel to the same degree. This lattices. The amount of heating necessary could have happened only if all the iron HAYDN to move the oxidized iron from the and nickel were once in the metallic matrix of the Renazzo and Tieschitz state, in the form of an alloy of nearly chondrites into their chondrules can be constant composition. "Sheer listening j oy!"-that's how Leonard Bernstein described estimated: 10 million years at 500 de The fractionation of iron with respect Library of Recorded Masterpieces grees centigrade, 40,000 years at 700 to silicon could have been accomplished exciting VIVALDI recording proj degrees C. or 1,000 years at 900 degrees simply by mixing the nickel-iron alloy ect. And now the London Times C. Evidence of such small-scale chemical with silicate minerals in different pro praises LRM's new HAYDN SYM migrations is common in metamorphic portions. It is not hard to imagine this PHONY series, recorded by the earth rocks. happening in a system of dispersed Vienna State Opera Orchestra un It seems that oxidized iron must have chondrules before they accreted into der Max Goberman: moved into the chondrules at some time planets. Chondrules contain varying "Recordings of exceptional after they were formed. There is chemi amounts of nickel-iron metal. The metal quality. Mr. Goberman has cal evidence that all chondritic material, rich chondrules are substantially heavier an extraordinary knowledge of including the chondrules, was once in a than the metal-poor ones. If chondrules Haydn's style." And, Roland Gelatt highly reduced state, with nearly all iron were dispersed in a turbulent gaseous in Reporter Magazine writes: in the form of metal. Chondrites can be nebula, some degree of sorting was "Goberman's sense of the sonic divided into several subclasses on the bound to occur, concentrating denser framework proper to Haydn is un basis of their chemical composition. metal-rich chondrules in one region and matched on records." Among the subclasses the atomic ratio lighter ones in another, just as sand and 18 of Haydn's masterpieces of iron in all forms to silicon varies wide pebble grains are sorted in stream beds. are included in the firstnine re ly [see illustration on next page]. Iron Both the Merrihue-Pepin findings and leases-newly recorded in mono evidently was fractionated in va rying the evidence that all chondri tic material and stereo-and ranging from the degrees with respect to silicon at some was once in a reduced state make it "Morning, Noon and Night" cycle stage in the history of chondrites. The seem fairly certain that chondrules were (Nos. 6, 7 and 8) to the powerful Nos. 96 and 98. Some are recorded for the first time; others for the first time in stereo; many for the first time are correctly played from the original scores with all the authentic instruments called for, under the supervision of, and with program notes by, the noted HA YDN scholar, H. C. Robbins Landon.

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CHONDRITES AND SUN show close correlation in metals content, indicating origin from 150 W. 82nd St., N. Y. 24, N. Y. common material. Gray hars represent chondrites; colored, sun. Only major variant is iron.

© 1963 SCIENTIFIC AMERICAN, INC among the planetesimals that conglom is possible to sketch the broad outlines. centration of mass-a protosun-at its erated to form the terrestrial planets. The space between stars in our galaxy center. Judging from the composition of chon is not really empty. It contains thinly The cloud was at first very cold, prob drites such as the Tieschitz and Renazzo dispersed gas (hydrogen, helium and ably about 50 degrees Kelvin (degrees stones, roughly half of the matter that neon) and tiny solid grains, ranging in centigrade above absolute zero). Col accreted was chondrules. The other half size from a hundred-thousandth to a ten lapse caused its gas to be compressed, -the black material between chondrules thousandth of a centimeter, in which all and this generated heat. At first the heat in these chondrites-is ultrafine-grained, the other elements are frozen. The den was radiated into space as fast as it was so that presumably it was dispersed as a sity of the interstellar gas is about one created. Then, as the cloud continued fine dust before accretion. It is similar in atom per cubic centimeter. to contract, the dust grains in it came over-all composition to the chondrules, The interstellar matter is not uniform closer together, causing it to become less except that its iron is oxidized. Later we in density. There are thin regions and transparent to radiation. Heat generated shall see why the matrix of a chondrite dense regions, and over long periods of by compression began to accumulate might contain oxidized iron whereas its time these Huctuate. It is believed that and the temperature rose. At higher chondrules do not. the Huctuations sometimes create a re temperatures hydrogen molecules ab

gion or cloud so dense and so large sorbed increasing amounts of radiation, The Primordial Solar System that self-gravitation-the attractive force storing the energy in the form of the exerted by each portion of the cloud rotation and vibration of molecules. This It is appropriate now to consider how on the rest of the cloud-overwhelms the further decreased transparency. Accord this background of information about other forces that act on it and causes ing to a recent theoretical study made chondrites and chondrules contributes the cloud to fall together. As it collapses, by A. G. W. Cameron and Dilhan Ezer to the reconstruction of the origin and its density everywhere increases, and of the National Aeronautics and Space early history of the solar system and, in soon particularly dense parts of the cloud Administration's Institute for Space particular, how the "fiery rain" of chon probably begin to collapse on them Studies, by the time the protosun had drules fits into the scheme. It is reason selves. The cloud breaks up into numer collapsed to 50 times the radius of the ably certain that planetary systems are ous collapsing subsystems, many with present sun its average temperature was a normal by-product of the condensation masses comparable to that of the sun. more than 3,000 degrees Kelvin, its cen of stars from interstellar clouds of gas It is supposed that the solar system was tral temperature was nearly 200,000 de and dust. Interstellar clouds such as the formed from one such collapsing cloud grees K. and it was almost completely Great Nebula in Orion [see illustration fragment. opaque to its own radiation. Previously on page 66] are often populated with Every cloud would have possessed the collapse of the system had been un stars of the types designated 0, Band T some angular momentum, or spin, be checked, but now mounting temperature Tauri, types thought to be relatively fore it began to collapse, if only because brought about gas pressures high enough young. Studies have been made of why it was part of a galaxy that is itself ro to balance the force of gravity that was and how a gas cloud would evolve into tating. As the sub cloud that was to be trying to pull the system together. Col a star, based on our knowledge of the come the solar system fell together its lapse ceased. inHuence of gravity, the behavior of angular momentum was largely con A sphere of gas in which gravity is gases as temperature and pressure vary served; it rotated faster and faster, as a everywhere balanced by pressure, and and the How of thermal energy in gas spinning figure skater rotates faster in which radiative heat transfer from one systems. The process is not fully under when he pulls in his arms. By the time region to another is prohibited, is said stood, and there are important differ it approached the size of the present to be in polytropic equilibrium. The pro ences in the models proposed by dif solar system, rotation had given the tosun was now in this state. Heat moved ferent astrophysicists; nevertheless, it cloud the form of a Hat disk with a con- comparatively slowly in gas convection

I I I BRONZITE CHONDRITES j I HYPERSTHENE CHONDRITES t , TYPE I CARBONACEOUS CHONDRITES TYPE II I • CARBONACEOUS CHONDRITES : ...� TYPE III I CARBONACEOUS CHONDRITES ;',::,';;:{ ,',,:. C·;:·y').'" I I I ENSTATITE CHONDRITES

, AMPHOTERITES I II I I I o .5 1 1.5 0 .025 .050 ,075 IRON /SILICON NICKELl IRON METALLIC ELEMENTS in chondrites indicate that chondritic the process that fractionated iron also fractionated nickel, since material was once in reducing atmosphere, such as solar nehula. the nickel·iron ratio is almost identical (right). The close asso·

Iron was fractionated in relation to silicon, as shown hy bars at left ciation of nickel and iron indicates that all the iron was in a giving atomic ratio of iron to silicon by chondrite subclasses. But metallic state, alloyed with nickel, at the time of fractionation.

© 1963 SCIENTIFIC AMERICAN, INC Sync om is an entirely new kind of communications Further, since Syncom remains in a controlled pcsi. satellite. It is the firstsynchronous satellite -the first tion, it can be used 24 hours a day for uninterrupted to "stand still" in space. communications to this entire area. In fact, in Syncom's firstmonth of operation, it logged Actually it is traveling 6,875 mph. But at its altitude of 22,300 miles, Syncom's speed matches the earth's more operating time than all other communications rotation . Result: It is "parked" over the earth. satellites had up to that time.

From this vantage, above the mouth of the Amazon Little wonder NASA has called Syncom a major break· River, Synco� can "see" 400/0 of the earth. Thus it through in the peaceful use of outer space. can beam signals to over one billion people in North Hughes Aircraft Company, under contract to NASA, is and South America, Western Europe and Africa. proud to have conceived, designed and built Syncom.

.... Syncom differs from other satellites in that it is precisely controlled in a high-alti tude orbit. Here it can be permanently "parked," while other types of satellites are in random, low-altitude orbits_ • Creating a new world with electronics Future Syncom system in development at r------, Hughes requires just three operatin'g I I satellites to extend telephone, telegraph, : HUGHES : I I and wire photo service to all the • ______TV L � HUGHES AIRCRAFT COt-IPANY populated areas of the world. � '--______---, --'

© 1963 SCIENTIFIC AMERICAN, INC currents from its interior to its surface, [see bottom illustration on page 72] there to be radiated away. Heat lost at by taking into account the thermody the surface had to be balanced by the namic properties and abundances of the generation of new compressional heat, substances in the gas phase and the INlclRI so that the protosun slowly contracted. properties of potential condensed ma By the time it had shrunk to nearly the terial (magnesium silicates and iron WHERE size of the present sun, its central tem metal) . perature had increased to about 20 mil We see that liquid droplets would be INITIATIVE lion degrees K., giving rise to thermo stable in the protosun only at rather IS ENCOURAGED nuclear reactions. A temperature was high pressures, more than one atmos finally reached at which thermonuclear phere (15 pounds per square inch) for reactions generated exactly as much heat liquid iron and more than 100 atmos NCR, a pioneer in the development as the sun radiated from its surface. pheres for silicate liquids. To be sure, of record-keeping devices, has been There contraction halted, and since then the bulk of the protosun would have developing systems and encouraging the sun has remained in essentially the been at higher pressures than these dur engineers for many years. Our techni same steady state. ing terminal stages of contraction. But cal people have made NCR a leader in our knowledge of the properties of poly the industry. Ca n yo u contribute to make it an even more successful Com The Evolution of Chondrules tropic spheres tells us that regions of pany in the yea rs to come ? If you feel high pressure would also be regions of you are such a person, you may be in The solid grains that were included enormously high temperature. Gas at a terested in the foll owing openings in in the collapsing cloud fragment would pressure of 1,000 atmospheres would Dayton, Ohio. have been evaporated at an early stage necessarily have a temperature of 100,- by increasing temperature. The metal 000 degrees K. or higher. Conversely, Senior Systems Design: Fa miliar • vapor they yielded, however, would have gas near 1,700 degrees would be at very ity with solid-state circuitry; creative; had a chance to recondense near the low pressure: a thousandth of an atmos desire to work at advanc ed develop ment stage. surface of the protosun as convection phere or less. The juxtaposition of high currents continuously moved the gas up pressure and moderate temperature-

• Thin Film: Mat erials research; de ward into regions of lower pressure and 1,000 atmospheres and 1,700 degrees vice development. temperature. Could chondrules be the necessary for the existence of liquid product of this condensation? droplets would not have been even re Chemist-Research: Ba ckground • Apparently not. The difficulty lies in motely approached in the protosun. Any in polymer chemistry; paper technolo the stringent physical conditions that condensation that occurred in the pro gy; adhesives; synthesis of dyes. have to be satisfied in order to have sili tosun convection cells must have been

• Logic and Circuit Design: Com cate liquids coexist with a gas of solar directly from the vapor state into solid puter and Systems Development. composition_ A diagram showing the grains, and laboratory experience tells

conditions for stability of magnesium US that the grains produced would have • Mechanical Design Engi neers: silicate liquids and iron-metal liquid been extremely small. Expert in sma ll mechanica l systems (the two principal constituents of chon It seems, then, that chondrules can design; integrated circuit packaging_ drules) in a solar gas can be constructed only have been made in the nebula sur-

• Operation Research: Commercial R&D Applications.

• Integrated Electronics: Adva nced concepts for computer development.

• Scientific Programming: Simu lation of different compute r systems. .. '

Most of these positions are at the graduate level, however, a bachel or's degree with appropriate experience will be sufficient qualifications for most openings_

Don't wonder what may be present for you. Drop us a line describing your � .. background and interests. We will con ••.. tact you to arrange for more detailed discussion.

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T. F. Wade, Technical Placement The National Cash Register Company Main & K Streets. Dayton 9, Ohio

An equal opportunity employer OXIDIZED IRON shown in color is concentrated between chondrules in primitive chon drite (le/t), hut during recrystallization it moves into chondrules, as represented at right.

© 1963 SCIENTIFIC AMERICAN, INC At a recent NABAC Convention held in The 31 5, operating under control of traveled neorly 4,000 miles and yet was Minneapolis, NCR demonstrated its On the On-Line Package Program devel processed in approximately thirteen sec Line Bank System and Software to hun oped by NCR , processed each trans onds. This demonstration convinced dreds of ban kers. action by selecting the proper account many bankers of the feasibility of plac Typical bank saving transactions were ...verifying the old balance ... updat- ing a computer at the "finger tips" of entered on a Class 42 Window Machine ing the central record ... establishing each teller. located on the conv ention floor and the required controls ...and returning For more information regarding the transmitted to a 315 CRAM Computer the updated transaction to the Class 42 On-Line processing capabilities of the System at NCR's Data Proces sing Center for printing in the customer's passbook. 315 CRAM Compu ter System, call your in Los Angeles, California. A transaction such as the above nearby NCR Office.

NCR PROVIDES TOTAL SYSTEMS -FROM ORIGINAL ENTRY TO FINAL REPORT THROUGH ACCOUNTING MACHINES. CASH REGISTERS OR ADDING MACHINES, AND DATA PROCESSING .• The National Cash Register Co l,133 offices in 120 countries · 79 years of helping business save money

© 1963 SCIENTIFIC AMERICAN, INC rounding the protosun. It is true that in most of the nebula temperatures were too low to allow the existence of liquid droplets; in general, metallic elements must have been present in the form of very fine dust grains. Some of these may have been original interstellar grains that never got hot enough to evaporate; others, grains of matter that condensed in the outer layer of the protosun and then found their way out into the nebula. Yet there must have been periods of high temperature and pressure in the nebula in which liquid droplets were stable; otherwise chondrites would not contain "abundant small bodies" that show the isotopic effect of particle bom bardment. The only ready explanation for these transient temperatures and pressures is that massive shock waves propagated through the nebula from time to time. During the passage of a shock wave [see top illustration on page 72] the nebula would at firstbe com pressed and compression would raise its temperature; then after a short time it would decompress and cool. In some cases during the heating phase the dust grains in the nebula evaporated, and dur ing the cooling phase the metal and metal-oxide vapor recondensed into liq uid droplets. The rapidity of cooling after passage of a shock wave is an attractive feature of this hypothesis. We have seen that some of the chondrules contain glass, and these must have cooled quite rapid ly-in a matter of minutes or less-in order to be quenched into glass and pre vented from crystallizing. There is every reason to believe that shock waves did traverse the nebula. Events must have occurred in the proto sun that are similar to the solar flares we observe today, and these would have in jected huge impulses of energy into the surrounding nebula. (Flares are thought to be caused by the local annihilation of part of the sun's magnetic field. The energy that had been bound up in that part of the magnetic field is then dissi pated in the form of a massive electrical discharge. ) The shock pressure need not have been as high as 1,000 atmospheres. There may have been a tendency for solid dust What can a Questar telescope do for you? grains to be concentrated in certain It will let you see and photograph the tiny crimson feathers of a cardinal, like this actual-size regions of the nebula-near its equatorial portion of a 14 by 17 print. The small red bird was 50 feet away. Questar will also bring to you an plane, for example, or in the stagnant enchanting new microscopic world of near things. And you may take this miniature seven-pound regions between eddies of turbulent gas. electrically driven observatory wherever you go, H so, after shock heating and grain to bring to your family the sun, the moon and the stars in all their awe-inspiring majesty. evaporation such a region would be rich Priced from $995. Our 32-page booklet on request. er in metal vapors than other parts of the nebula. The diagram at the left at QUIESTA� the bottom of page 72 locates the liquid region on the assumption that metal BOX 20 NEW HOPE. PENNSYLVANIA 80

© 1963 SCIENTIFIC AMERICAN, INC on target with Minuteman, Titan III and Apollo-Allison pioneered a complete technology in flight-weight rocket motor cases for the 1st and 2nd stages of Minuteman. Result: A 10 0% re liability record in test firings over the past 5 years, case weight cut 57%, costs reduced 84% . Because of this record, we've been selected to participate in our nation's moon mission by building service module engine ta nks for Apollo-are working on thrust vector control pr essure vessels for the next generation booster, Titan III-and applying our rocket case technology to other space and missile projects. The ability to create new technologies where none exist: Another reason our aerospace and nuclear programs are on target. �li5011

Prime contractors-Minu teman: Thiokol Chemical Corporation and Aerojet General. THE ENERGY CONVERSION DIVISION OF Apollo: North American Aviation, Inc. Titan III: United Technology Center. GENERAL MOTORS, INDIANAPOLIS, IND.

© 1963 SCIENTIFIC AMERICAN, INC vapors were just as abundant in the nebula as they are in the solar atmos phere today. If, however, metal was locally concentrated in the nebula, the pressure requirement for liquid conden sation in the metal-rich region would be decl'eMed by the same factor as the metal concentration was increased. For example, liquid stability in a region where metallic elements were 100 times more abundant than was average would require a pressure of about 10 atmos pheres, not 1,000. Return The Two Types of Condensate After the passage of a shock wave, gas would not always cool through the region of pressure and temperature re to . Research quired for the condensation of liquid droplets, so that much of the reconden sation during cooling would have yielded very small solid grains. In time both in Britain types of condensate-chondrules and fine dust grains-would occur mixed together in the nebula. Are you a British scientist in Canada Although the gas was a reducing en thinking of returning to work in Britain? vironment at high temperatures and pro duced chondrules with little oxidized You may fi nd what you are looking for, iron, at low temperatures the same gas without having to go home first, in the is capable of oxidizing iron. Below 100 Civil Service, the United Kingdom Atomic degrees C. water vapor in the gas tends Energy Authority, or the Central Electricity to turn iron metal to magnetite. Because of their small size dust grains made of Generati ng Board. iron would be quickly oxidized. But most iron metal in the chondrules would Research Fellowships be shielded from oxidation because of its and Permanent Appointments coarser grain size, and also because it is There are openings in all branches of often buried inside silicate minerals. Consequently, if the condensate parti science. The order in which they are most cles were not exposed to cool gas for a numerous is (i) physics, mathematics, very long time but instead soon conglom engineering, and metal lurgy; (ii) chemistry erated into planets, we would expect the and biochemistry ; (iii) biology. The accreted matter to consist of metal bearing chondrules mingled with fine researc h ranges from the most fundamental grained magnetite-bearing material. This to the most applied. curious juxtaposition of highly reduced and highly oxidized matter is precisely A selection board of scientists will what we find in the primitive chondrites be coming to Ottawa on 7th January 1964 of Renazzo and Tieschitz. If you would like an appointment with them, It is quite likely, then, that chon drites-and in particular their chondrules would you write by 11th November, 1963, -are witnesses of the time when the to : Mr. P. C. Davidge, Senior UKAEA solar system was bom . This is an excit Representative in Canada, c/o Atomic ing idea. Only recently have we begun to study chondrules as entities. They Energy of Canada Ltd., Chalk River, contain a wealth of information-isotop Ontario. ic, chemical, mineralogical-about the processes that have acted on them. We An announcement to British scientists in the U.S.A. willbe made may be able to learn about the nature in November and evolution of the solar nebula, the

Issued jointly by the Civil Service Commission, formation of the planets, some stages of the U.K. Atomic Energy Authority, and the the evolution of the sun and the time Central Electricity Generati ng Board scales for all these processes. The chon drules have begun to tell a faSCinating story.

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