California In stitu te

of Technology

EN G I N EE

Volume LX , Number 2,

I 9 9 7

IN THIS ISSUE

The Neuroanatomy

of Vision

Radar Looks at Asteroids

A Peek at Caltech's

New President Caltech President-Elect David Baltimore greets members of the faculty (Associate Professor of Chemical Engineering Julia Kornfield, right, and Norman Brooks, the Irvine Professor of Environmental and Civil Engineering, Emeritus. left) after the announcement of his appointment on May 13. Behind them are, from left, Peter Dervan. the Bren Professor of Chemistry and chair of the Division of Chemistry and Chemical Engineering; Gordon Moore, chair of the Board of Trustees and of the trustees' presidential selection committee; and Kip Thorne, the Feynman Professor of Theoretical Physics and chair of the faculty presidential search committee. Baltimore and his wife, Alice Huang, will move to Pasadena in the fall, when he will officially take office. Baltimore's Impressive research career is outlined in a story beginning on page 32. California Institute

of Technology

2 Random Walk

11 The I O-Foot Wi nd Tunnel: Ove r an d Out A piece of aviation history flies off into tbe sunset, or, rather, heads east by truck.

14 Rad a r Obse r va tions of Earth-Approaching Asteroids - by Steven J. Ostro l ong the province of supermarket tabloids, killer asteroids are actually worthy of serious study. A group at JPl find'i them to be quite a remarkable rock collection.

24 How We See - by Richard A. Andersen Cu ltech biologists arc beginning to find out what goes on in our brains when we see somerhing move.

32 D avi d Baltimore: A Short Portrait of a Long Career - by Douglas L. Sm ith Calrecb's incoming president won the Nobel Prize back in 1975, and be hasn't ",if exactly rested on his laurels since tben. .. ' './ 38 Obituaries

43 Facu lty File

On the cover: In 2004, an Engineering & Science (ISSN 0013-7812) is published Thomas J, Tyson Preside1lf o[ the All/11m; AJJoc;a/;oll asteroid named Toutatis quarterly at the California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91 125. Annual J. Ernest Nunnally will whi z by Earth at a dis­ subscription $10.00 domestic, $20.00 foreign air mai l; Vice PreJide1lf for IlISlilllle Relaliom tance of fou r lunar orbits. single copies $3.00. Send subscriptions [0 Calte<:h 1-7 1, Robert L O'Rourke Pasadena, CA 91125. Third class postage paid at Pasade­ AJJociale Vice Presidelll [orimlillilt Rela/iom If you were ~a(at i on in g on na, CA. All rights reserved. Reproduction of material con­ Tou tatis then, this is what rained herein forbidden without authorization. © 1997, STAFF: Edilor - J ane Dietrich you'd see. Earthbound Californ ia InstitUte of Technology. Published by Cal tech and the Alumni Association, Te lephone: 626-395-3630. MaJ1agiJ1g Editor - Douglas Smith radar astronomers are COJ1lrihuting \Vrifer - Robett Tindol taking close looks at a PICfURE CREDIT'S: Cover - E. De Jong, S. Suzuki, S. Hudson Copy Edilol'J - Michael Farquhar, & S. Ostro; inside covers, 8, 9, ! 1, 12, 13,32,43, 4ti - Bob Paz; Danielle Gladding, Julie Hakcwill , num ber of Earth- 3 - J ane Dietrich; S - David Wald; 7, ! ti, 16 - JilL; 19 - Steven Anne Sommer approaching asteroids, as Ostro; 21-23 - De Jong & Suzuki; 24, 30 - David Brad ley; 26, BusilleJS "{allage,. - Debbie Bradbury 28-31 - Richard Andersen; 26 - Fritz Goro; 27 - Bruce Whict:­ Cimt/alioll Mflllagel' - Susan Lt:e you'll see on page 12. head; 34,35 - MlT; 35 - Tobbc Gl1stavsson/Reporwgebild Photographer - Robert Paz Images of the gamma-ray burst field obtained at the lOO-inch Hale Telescope at Palomar Observatory on May 9 (left) and 10 (right) show the visible-light brightness of the optical counterpart (arrow) still rising. The gamma-ray burst was first detected May 8.

Random Walk

bursts was quite crude, leaving astronomers with GAMMA-RAY BURSTS DEMYSTIFIED thousands of faint stars and galaxies as potential "hosts." An important recent develop­ ment was the deployment of In Maya ceam of Calcech some as-yet unknown popu­ BeppoSAX, a joinc Iealianl astronomers solved one of lation of objects within our Dutch satellite launched in astronomy's most incriguing own Milky Way galaxy; and lace 1996 by the Iealian space mysteries, pinpointing for a anorher that proposes that the agency. This satellite, for the gamma-ray burst an optical bursts originate in distant first time, provided a rapid counterpart several billion galaxies, several billion light­ and accurate position in the light-years away from the years away. If the latter is sky for strong gamma-ray Milky Way. The resulcs true (as was indirectly bursts. This enabled astrono­ "When I finished analyzing demonstrate for the first time supporced by che Compcon mers to search for possible the specttum and saw fea- that at least some of the enig­ Observatory's earlier observa­ visible and radio counter­ matic gamma-ray bursts that tions), then the bursts are parts, using telescopes on the tures, I knew we had finally have puzzled astronomers for among the most violent and ground. The first such decades occur at very great brilliant events in the universe. counterpart was deteCted at caught it. Ie was a stunning distances and nor, as some Gamma-ray bursts occur che beginn.ing of May, buc have thought, inside our own a couple of times a day, says faded away before its nature moment of revelation." galaxy. Shci Kulkami, professor of could be escablished. The burses of high-energy astronomy and planetary The satellite detected radiation were first discovered science and one of the team another burst on May 8, and by military satellites almost members. These brilliant Cal tech astronomers were 30 years ago, but so far their flashes seem to appear from able to bring telescopes at origin has remained a mys­ random directions in space Palomar Observatory to bear tery. New information came and typically lase a few within a few hours. The in recent years from NASA's seconds. "After hunting clues Cal tech team noticed a star­ Compton Gamma-Ray to these bursts for so many like object that was changing Observatory satellite, which years, we now know that the brightness in an unusual has so far detected several bursts are in fact incredibly fashion at the position of the thousand bursts (see E&S, energetic events," said bum. (Dr. H oward Bond of Wincer 1992). Nonecheless, Kulkarni. the Space Telescope Scie.nce the fundamental question of Progress in understanding Institute initially reponed where the bursts came from the nature of the bursts was the object based on his remained unanswered. stymied by the fact that until measurements at Kite Peak Competing theories on recently the bursts were National Observatory.) gamma-ray bursts have gen­ detected as very high-energy The crucial piece to the erally fallen into two catego­ gamma rays. It is difficult to puzzle was finally found by ries: one that suggests that focus gamma rays, and thus che Calcech ceam on May 11 the bursts to originate from the positional accuracy of the using one of the two W. M.

1 ENGINEERING & SCIE NCE NO. 1997 Keck lO-meter telescopes, Professor of Astronomy the world's largest, on Mauna Charles Steidel (PhD '90); Kea, Hawaii. The starlike postdoctoral scholars Steven object showed features known Odewahn and Debra Shep­ co originate in inrergalactic herd; and graduate students 626 clouds in its spectrum. By Kurr Adelberger, Roy Gal, measuring the wavelengths and Michael Pahre. The team Longtime residents complain that the San Gabriel Valley of these features, the Calfech also includes Dale Frail of the doesn't have an identity of its own. Not any more--on June astronomers were able co National Radio Astronomy 14, 1997, the area code for che San Gabriel Valley, and wich measure the distance co a Observatory in Socorro, New ic Calcech, changed co 626. The old 8 18 area code will still gamma-ray burst for the first Mexico. work chrough February 21, 1998, however. And che time. Their measurements "Gamma-ray bursts are one telephone company in its infi nite wisdom has decided that place the burst at a distance of the great mysteries of Burbank, Glendale, and La Canada Flintridge belong co the of several billion light-years, science," said Djorgovski. "It San Fernando Valley, wh ich retains the 8 18 area code. Thus over one-half the size of the is wonderful to contribure CO the J et Propulsion Laboratory's area code remains 818, observable universe. its unraveling." 0 because although JPL's mailing address is in Pasadena, the Mark Metzger, assistant vast majority of the facility li es in La Ca nada Flintridge. professor of astronomy, said In other telecommunications news, Cal tech's Office of he was chrilled by che resulr. Public Events has changed its tOil -free number from "When I finished analyzing (800) 423-8849 co (888) 2-CALTECH . the spectrum and saw features, I knew we had finally caught it. Ie was a stunning moment of revela­ tion. Such events happen only a few times in the life of a scientist." fly By Recent observations from the telescopes at Palomar show that this starlike object is fading away. Because such rapid fad ing had been seen When Ari Hoffman, a with the burst in March, the sophomore at Tamalpais High Calrech as tronomers had to School in Mill Valley, Cali­ make an extra effort to fornia, entered his Drosophila identify this counterpart project in the Marin County quickly so chac che Keck science fai r, he never dreamed observations could be carried he would run afoul of animal out when the object was rights. H offman, whose brighc. study involved the effects of The discovery is a major radiation on the fruit flies' step toward helping scientists reproduction patterns (num­ understand the nature of the ber of offspring and percent­ Ed Lewis shows Ari Hoffman the view from his lab. burst's origin. We now know age of mutations), won first that for a few seconds the prize in the science fair, only burst was more than a million to see it withdrawn because of times brighter than an entire alleged "cruelty to animals." won him the 1995 Nobel California for yet another galaxy. No other phenomena About 35 of his 200 flies had Prize, sent Hoffman a check science fair. On May 20 the are known that produce this died before reaching che end "as a token award for your cwo stopped by for lunch ac much energy in such a short of cheir normal 10-day life accomplishments." Lewis the Athenaeum and a look time. Thus, while the obser­ span. had also begun working with through Lewis's microscopes vations have settled the ques­ Hoffman's prize was even­ Drosophila when he was in at Drosophila chromosomes. tion of whether the bursts tually reinstated, but nOt high school back in 1934, che "Cool," Hoffman said. Lewis come from cosmological dis­ before a story in the San beginning of a long and fruit­ also gave him a few samples tances, their phys ical mecha­ Francisco Examiner attracted ful career studying genetics of his famous mutant, four­ nism remains shrouded in the notice of Nobel laureate wi th this tiny organism. winged fly, the creature that mystery. Ed Lewis (PhD '42), Calcech's Thac was before che days of had enabled Lewis to show In addition to Kulkarni Thomas Hunt Morgan science fairs, Lewis noted in how genes control the body's and Metzger, che Calcech Professor of Biology, Emeri­ his letter to the student. arrangement. The flies were team consists of Associate tus. Lewis, probably the Lewis also invited Hoffman dead, of course, but had Professor of Astronomy most noted living fly geneti­ to visit Caltech when he and served science well. D-JD George Djorgovski; Assistant cist, whose work on fruit flies his father came to Southern

1997 ENGINEE RING & SCIE N CE N o .2 ] N icole Kidman, and the prof probably by Alan Arkin (or SONOLUMINESCENCE, CAMERA, ACTION! maybe-l kid you nor­ Marlon Brando). By the time the movie actuall y gor made. Kidman had been traded for a starlet and It W4m't "ominated for al/ claiming to be a Hollywood Branda had been downsized Oscar (and 110 one is selying it director. "Yeah, right! " I to Morgan Freeman. should hftve been), bllt last fall's remember thinking as I Gene called me because movie Chain Reaction had d ialed the number. It rurned of my work on so nolumines­ hidden links to Calteeh, Former Out that the caller, Gene cence and other chemical Lloyd HOllse president Ken Serdena, was the set director effects of high-intensity Slts/ick (BS 74), now the of a Twentieth Century Fox ultrasound. He wanted to \'(Iitliam H, & j anet LycctfJ movie tentatively tided Dead visit our labs [0 see what a Professor o[ ChemiJ/'IY at the Drop. then in preproduction. chemistry lab actually looks University of Illinois at The movie was to be about like. So Gene and his assis­ UrhallcI-Champaign, became a a Nobel-laureate professor tant drove in from Chicago Minor technical errors-such hig noi.re in the study of liltra­ and hi s graduate student, for a visit. With video and as violations of the laws of sOlmd-ultm-high-freqliency who discover the use of still cameras, they shot evety­ sound waveJ-in the early so nol u mi nescence-the thing that didn't move. It t hermodynam ics-are 1980s (see E&S, Spring 1994). incandescent glow generated was fun showing him around Here he ,-ecom1tJ hoUJ his ,'esearch when liquids are irradiated and trying to explain why obviously no problem for led Hollywood to come calling in with ultrasound- to catalyti­ things were set up the way central Illinois. (This article is ca ll y produce unlimited they were. They even gave Hollywood. rcpri1lted courtesy a/Inside quantities of hydrogen (the disposable cameras to my Illinois, the faCltllylstaff 11eWJ­ ultimate clean fuel) from graduate students and myself paper of tbe University of Illinois water. (Minor technical to see how we live. Cinema at U,·ba114-Champaigll.) errms-such as violations verite, at least for the set of rhe laws of thermodynam­ desig n! Some of you may have seen ics-are obviously no prob­ A week later, Gene called a movie las t fall called Chain lem for Hollywood.) The agai n. Now he wanted to Reaction. If so, you have my professor is killed when the rent equipment from the lab condolences. Nonetheless, it bad guys rry to steal the for the set. I explained to isn't too often that a chemist discovery, and the intrepid him that we do actually use finds himself involved with graduate student runs this stuff and that it's very Hollywood, much less gets through chase sce ne after expensive equipment. He money for his school off a chase scene to expose rhe sounded disappointed, and bad movie. evildoers. This is no surprise, then it hit me-he doesn't One pleasant fall day in si nee rhe director is Andrew want equipment that works, 1994, I found on my chair­ (The Fugitive) Davis. Serdena only that looks like it works. the only safe place to leave a told me that the grad student And I knew about this caver­ slip of paper in my office- a wou ld be played by Keanu nous storage area in the base­ phone message from someone Reeves, the love interest by ment of Roger Adams Lab rhar was full of old equip­ Cbttin R,m/;"' '' 1996 T"·enri~ .h C"ntury f ox Film Corp. All rights u-servN. ment- ancient Infracord spectrophotometers. several dozen old black-and-white It's a nail-biting moment for Keanu monitors, prewar lathes (not Reeves (left), Morgan Freeman (to sure which war), and so on­ a1l stuff too good to throw his right), and other "scientists" away at the time it was on a set that probably came from hauled down rhere, but of the collection of pre-owned lab no use now. I suggested that equipment in Suslick's basement maybe they'd like to see the "scientific equipment" in our storage. ("Who uses dials storage area. His assistant anymore?" says Suslick. returned to Champaign and, "Not even the Russians.") with flashlights in hand, we went spelunking into the deprhs of RAL She phoro­ graphed everyrhing (again)

4 ENGINEERING & ~(lfNCE NO . ' 997 and went away. W hen Gene called next, about 48 hours later, I could practically hear him salivat­ ing over the phone. This room full of useless equip­ ment turned out to be just the sort of place a set director dreams about (apparently set Prototype CAL TECH/COM G/USGS Rapid Peak Vel odty Contour Map directors have very weird Conto ured Ve loc it)' in eml sec dreams). But how do we sell this detritus of dead equip­ ment to them? We found that the university cannot sell 36°N equipment-no matter how useless- withou t rampant rivers of red tape. We could , however, declare old stuff surplus once it was of no further use, and simply take it off the books. W hether the junk then went into a dump­ ster or into a truck made no difference. 35°N So, with help from our business-office manager, I arranged for a donation of $10,000 from Twentieth Century Fox to the schooL I didn't even ask a finder's fee. Fox then sent down a crew of fo ur humongous guys and a moving van to match, and they spent a full day hauling 34°N away junk that we'd been wondering how to get rid of fo r years! Two years later the movie came out, now called Chain 11 ffW 117'W 116°W 11 SOW Reaction. On opening day, we shut down our lab, and I took On March 18, a magnitude 5.4 aftershock of the Landers earthquake rattled the whole crew out to the first matinee. I bought the much of Southern California. What was really earthshaking, however, was tickets, but my students had the debut this provided for TriNet, a new seismic network operated jointly to get their own popcorn. by Caltech, the U.S. Geological Survey, and the California Department of Afterward, we agreed that the best part of the film was the Conservation's Division of Mines and Geology. Seismologists were able to labs, which were only slightly determine the quake's magnitude within five minutes-a tremendous hokey. In fac t, that was just Oops! improvement over the time it once took to confirm data-and in another about the only good thing in five (practically before the TV crews could arrive!) they had created this the entire movie. Even Siskel The portrait of turbu­ and Ebert gave it thumbs lence that Engineering & contour map (above) of peak ground velocities. The red star marks the down. Fortunately, the VI's Science ran on the cover of epicenter, the red lines are faults, the blue lines are freeways, and the School of Chemical Sciences Issue No. 3 for 1996 was yellow contours are in centimeters per second. The triangles are seismo­ was not listed in the credits, unattributed) due to an graphic stations- blue for the Division of Mines and Geology, orange for so our anonymity remains editorial error. Our preserved for posterity. Until apologies to postdoc Caltech/USGS digital stations, and green for analog stations. The maps now ... D David Laidlaw) who gen­ show at a glance what areas might and might not have suffered damage, in erated the image and was a way that merely quoting magnitudes and epicenters cannot. The maps kind enough to provide a copy for us. also go up on the World Wide Web (http://www-socal.wr.usgs.gov/pga.html) the moment they're made.

1997 ENGINEERING & \(IEN([ NO. • DNA REPAIR KIT

Cal tech chemists have DNA to its normal stace. ers have found. However, found a way to repair DN A The research is al so signifi­ the effi ciency of the reaction molecules char have been cant in that the rhodium is diminished when the base­ damaged by ulcravioier complex can be attached to pair stack- the pathway radiation. Professor of the end of the DNA strand for elecreon transfer-is Chemistry Jacqueline K. and repair the damaged site disrupted. Barton, postdoc Peter J. even when it is much farther "This argues that the Dandliker, and grad scudenr up the helix. radical , or electron hole. is R. Erik Holmlin repocred in "What I think is exciting is migrating through the base the March 7 issue of Science that we can use the DNA co pairs," Barton says. "Whether that rhe new procedure carry out chemistry at a dis­ electron rransfer reactions on reverses thymine dimers, a cance," says Barron. "What DNA al so occur in nature is well-known type of DNA we 're really doing is transfer­ something we need to find abnormality caused by ex­ ring information along the out. We have found that this posure to uJtravioler light. helix." feature of DNA allows one to By designing a synthetic A healthy DNA molecule carry out chemical reactions molecule comaining rho­ appears something like a from a discan ce." Barton dium. rhe researchers have twisted ladder. The two ca utions that the discovery succeeded in repairing the "rails" of the laddet, the D NA does not represent a new form damage and returning the backbone, are connected wich of chemotherapy. However, "rungs," the DNA bases the tesearch could point co adenine, thymine, cytosine new protocols for dealing and guanine, which are paired with the molecular changes W AITI NG TO E XHAL E togecher in unics cal1ed base that precede mutations and pairs co form the helical can cer. "This could give us· In less earthshaking developments at Caltech and the stack. Thymine dimers occur a framework to consider new USGS, Ken Hudnut and his colleagues have been monitor­ when rwo neighboring thy­ strategies," she says. ing the gradual squishing shut of the Los Angeles basin mines on the same strand This research was funded for the last year and a half now, using a network of Global become linked cogether. The by the National Institutes of Positioning System (GPS) receivers. One of these receivers is dimer, once formed , leads to Health. Dandliket is a fellow located amp the Pacoima Dam, where, says Hudnut, "we've mutations because of mis­ of the Cancer Research Fund seen the center of the arch of the dam deflect downstream pairings when new DNA is of the Damon Runyon-Walter then back up again, and then down again." The moveme~t made. If the thymine dimers Winchell Foundation, and is about two centimeters (about three-quarters of an inch), are not repaired, mutations Holmlin is a National Science and it takes roughly a year per oscillacion. "We think chis is and cancer can result. Foundation predoctoral due to the warming and cooling of the whole structure wich The new method repairs fellow. D--RT seasonal climate changes," Hudnut explains. "It's pretty the thymine dimers at the cool that such a large structure 'breathes,' and that we can very first stage, before muta­ measure ic. It's not like the dam is about to fail or anything. tions can develop. The rho­ For all we know, it's been flexing like this ever since it was dium complex is exposed co built in the late 1920s-it's jusc never been observed before normal visible light, which now." If you'd like to see for yourself, there's a World Wide triggers an elecrron transfer Web page at hrep;l!www-socaLwLusgs.gov/scign/hudnut/ reaction co repair the chymine dam.htmi. dimer. The rhodium complex But failure is ultimacely what it's all about. Ever since can either act locally on a Northridge, Calcech's civil engineers have been realizing thymine dimer lesion on that ground displacement and velocity contribute more to the DN A strand, or can be earthquake damage than does acceleration (see E&S, Summer tethered to the end of the 1995). But old-fashioned seismographs measured accelera­ DNA helix to work at a tion best, so che building codes have been based on that distance. In the latter case, data. Combining digital seismological and GPS data should che electron works its way lead to a much bereer understanding of what happens co a through the stack of base structure when you shake it, and eventually to more earth­ pairs. The repair efficiency quake-resistant buildings, overpasses, and dams. 0 does n't decrease as the techer -DS point is moved away from rhe site of damage, the research-

• ENGINEERING & SCIENCE NO • ' 997 deposits, and further, were characteri stic of a widespread region. Kirschvink and Evans say that the preliminary implica­ tions are that Earth can so mehow manage CO pull itself out of a period of severe glaciation. Because ice and snow tend co reflect sunlight much bereer than land and water, Earch would normally be expected to have a hard time reheating itself in order to leave an ice age. Thus, one would expect a Snowball Earth to remain forever. Yet, the planet obviously recov­ ered both times from the severe glaciation. I( this looks like a close-up o( a "We think it is likely that the intricacies of global cli­ shattered plate to you, you're not SNOWBALL EARTH mate feedback are not yet (ar wrong. The plate, however, is completely undetstood, the icy crust o( Jupiter's moon especiall y concerning major Europa as seen by the Galileo deparcures from today's cli­ Those who think the win­ such an extenr---one less than mate," says Evans. "If the spacecraft. The individual ter of '97 was tough should a bi ll ion years ago during the Snowball Eatth model is COf­ (ragments are up to 13 kilometers be relieved that they weren't Neoproterozoic Era, and the rect, then our planet has a (8 miles) across, and you can see around 2.2 bi llion years ago. one that has now been remarkable resilience to how they have drifted apart from Scientists have discovered discovered from the Paleo­ abrupt shifts in climate. evidence for an ice age back proterozoic Era 2.2 billion Somehow, the planet recov­ one another, rotating slightly in then that was severe enough years ago. ered from these ice ages, the process. The scene looks to partially freeze over the "The young Earch didn't probably as a result of remarkably like aerial views of the equator. Professor of Geo­ catch a cold very often," says increased carbon dioxide­ biology J oseph Kirschvink Evans, a graduate student in the main greenhouse gas." spring break-up of oceanic pack ice (B5, M5 '75) and grad Stu­ Kirschvink's lab. "But when Evans says that an asteroid on Earth, (ueling speculation that dent Dave Evans have found it did, it seems co have been or comet impact could have an ocean o( slush or even liquid evidence that glaciers came pretty severe." caused carbon dioxide to pour water lurks just beneath Europa's wi thin a few degrees of the The researchers collected into the atmosphere, allowing equator's latitude when the theit data by dtilling rock Earch to crap solar energy and frozen surface. This high­ planet was about 2.4 bi ll ion specimens in South Africa reheat itself. But evidence of resolution image (the smallest years old. They base theit and carefully recording the an impact during this age, visible detail is 54 meters, or 59 conclusion on glacial deposits magnetic directions of the such as a crater, is lacking. yards, across) was shot on discovered in ptesent-day samples. From this informa­ Large volcanic outpourings South Africa, plus magnetic tion, the researchers then could also have released a lot February 20. 1997, from a distance evidence showi ng where computed the direcrion and of carbon dioxide, as well as o( 5,340 kilometers (3,320 miles), South Africa's crustal plate distance to the ancient north other factors, such as sedi­ during Galileo's sixth orbit of was located at that time. and south poles. The con­ mentary processes and Based on that evidence, the clusion was that the place in biological factors. A~ any Jupiter. Fo r more Galileo images, Cal tech researchers think tbey which they were drilling was rate, the evidence for the check out their World Wide Web have documenred the ex­ 11 degrees (plus or minus five robustness of the planer and site at http://www.jpl.nasa.govl tremely rare "Snowball Earth" degrees) from the eq uator the li fe that inhabits it is galileo. phenomenon, in which vir­ when Earch was 2.4 billion encouraging, the researchers tually the entire planet may years old. Plate tectonic say. Not only did Earth pull have been covered in ice and motions since that time have itself out of both periods of snow. According to Kirsch­ caused South Mrica to drift severe glaciat ion, but many vink, who originally proposed all over the planet, to its of the si ngle-celled organisms the Snowball Earch cheory, current position at abou t 30 that existed at the time there have probably been only degrees south latitude. Addi­ managed to persevere. D two episodes in which glacia­ tional tests showed that the - RT tion of the planet reached samples were from glacial

1997 ENGINEERING & SCIENCE NO . 7 David Wales, professo r of mathematics and master of student houses, leads the academic procession of candidates for the BS degree in 1997.

WOMEN AT CALTEeH: NOT 25 YEARS, BUT 53 OR 42 OR •••

In 1'espome to the notice il1 the experience did not prepare This demonstrates the heat of last issue ofE&S on the 25th me for a non-coeducational the argument, but the remark anniversary of women at ealtech, universiry! was actually not quite fair, Ham Liepmaml, the Theodore In the late '40s, 1 believe, since the lineup of votes was von Karman Professor of when 1 was a relatively young by no means according to age. Aeronautics, Emeritlts} and member of the voting faculty, In 1950, Richard Feynman former director of GALCIT, we had to vote on the pro­ was considering whether or pointed Ottt that we had written posed admission of female not to accept a permanent mz!y abottt undergradttate graduate students. I cannot professorship at Caltech. women. H e thought that the remember whether this vot­ Paco Lagerstrom, who had struggle to admit female graduate ing by the faculty was sup­ known Feynman when they stltdellfS abo merited mentioll, posed to be a poll only or had were both students at Prince­ and he provided .fome 'reminiJ­ more decision power. Of the ton, and 1 had either lunch or cences of his own. pro and con arguments, I can dinner (1 have forgotten remember only one, possibly which) with Feynman in the 1 arrived at Cal tech in because it was so silly: "If Athenaeum. Debating the September 1939 to work as YOll flunk a girl in class she pros and cons, we proposed an (unpaid) postdoc in the will cry on your shoulder!" that if Feynman should turn Guggenheim Aeronautical was proclaimed by someone down the offer, he should laboratories. Due to the out­ against. This was answered help the cause by giving the break of the war in Europe by a loud, but anonymous, £'lilure to admit women as a Hans Liepmann and various visa problems, voice from the back: "Now, reason. Fortunately for all of my wife arrived a few months what's wrong with that?" us, he accepted the offer, and later. When she inquired In any case, after a rather so, unfortunately, nothi.ng about the possibility of con­ heated debate in the H all of came of our proposition. But tinuing her physics studies, the Associates of the Ath­ a little later, the faculty vote we found that Cal tech did not enaeum, the motion was was reversed anyway. accept female students. 1 defeated by three votes. In 1944 or thereabouts, confess that this possibility When we filed out of the a young female aeronautical had flat occurred to me at room, Charlie De Pri rna, a engineer applied to complete all. 1 had seen many young then equally young professor a master's degree in aeronau­ women on the campus; I of mathematics, slapped me tics at Caltech. Her husband realized that in an institute of on the back and said in a worked,I believe, at lock­ technology comparatively few rather loud voice: "Don't heed. 1 don't know exactly women could be expected, worry, Hans; three of the old how she was permitted to but my middle-European guys are likely to die soon!" enter, but Gertrude Fila took

8 ENGINEERING & SCIENCE NO. 1997 classes and worked with me on a research project. keeping her one-year-old so n in a HOPE AND GLORY playpen between tWO wind runnels. We even published a paper together. Mrs. Fila's c1asswork was graued, but she Unseasonable rain fe ll early working in 1991 "with did noc get credit toward a on the morning of June l 3, structural biologists and degree; however, Clark Milli­ bm by 10 a.m. the skies were medicinal chemists (Q res t kan had cold her that when­ clearing and Calrech's l03rd small chemicals that might ever Cal tech accepted female Commencemenc commenced. intercalate into the catalytic graduate students, she would Some 202 students rece ived site of the HIV protease, an ger her MS degree, thei r bachelor of sc ience enzyme essential for the When I became director degrees; 104 master of science production of infectious of GALClT, I discovered degrees, 6 engineer deg rees, progeny virus." H e spoke of co rrespondence in the files and 173 PhDs were awarded, the overwhelming excitement indicating that Mrs. Fila, Dr. David Ho, BS '74, di ­ they felt when they realized David Ho, BS '74, speaks to the that they could inhibit the then teaching at Oklahoma rector of the Aaron Diamond graduating class of 1997. A&M, had as ked fo r her AIDS Research Center at protease enzyme, thereby degree and been turned down Rockefeller University, and blocking viral replication in because the requirements had Time magazine's 1996 Man of the test tube. HIV was largely a latent virus changed. With a li ttle noise the Year, gave the commence­ Three years later, they were was completely shattered ." from me. rhis decision was ment address-"Science as able to administer to HIV­ Later in his talk, Ho, who repealed, and Gertrude Fila, a Candle of Hope," Ho infected patients one of the came with his family to Cali­ by then a gray-hai red pro­ touched briefly on his own chemicals they had found. fornia from Ta iwan when he fessor, marched up with the Cal tech experience: "As a Ho described the "joy and was 12 years old, reflected on graduate students and finally young boy growing up in amazement as we watched the contribution of his heri­ gor her degree in 1974, Southern California, this was the level of HIV fall ever so tage to hi s career- the Asian my dream school. It is dramatically. At fi rst we respect for intellectual The barriers fi1lally fell, and the place where I fi rst learned did not know that we were achievement and hard work. th,y fell SlIddenly, Whmjack to tackle research with a si tting on top of a funda­ But, he remarked, "I have Roberts, now institute Pro/eHor multidisciplinary approach mental discovery in AfDS been an American for so long of Chemistry! Emeritus, was not limited by arbitrary research." Bur then, when that 1 have nearly forgorten recruited to the famlty Fo", MIT boundaries that separate they asked the right ques ­ that I am also an immigrant. in 1952! he had! according to biomedical sc iences fro m tions, "it quickly dawned on From ti me to time, I can still his oraL history in the CaLtech physics, chemisu y. engineer­ us that HIV must be turning sense the desi re that burns in Archives! /o/lr very, very good ing. and mathematics." over mpidly, in a dynamic the belly of a new immigrant, grad students who UJere interested He told the graduating equilibrium with the hos t. the des ire to carve our a place in coming ·with him to CaLtech. class that they had chosen Using dara from our patients in the new world. in the land One 'Was Dorothy Semenow. "a noble profession, one filled and working together with of opponunities .... Through­ LinliS PaJtiing told Roberts that with excitement," and ill us­ mathematicians, we proved Out its history, America has although the faCIlity and trmtees trated this claim with the that HIV replication in vivo continuall y benefited from had voted against admitting srory of his own recent dis­ was mpid and remorseless. the drive, labor, and creativi ty women, they had never considered coveries. Ho described how In the course of only a few of immigrants, many in the a specific CflSe, and he urged her he and his colleagues were weeks, the old paradigm that fie ld of science," 0 to apply, Panling put his own co nsiderable dOltt behind the ca.re, andby} tme 1953 itwas adotze deal. Dorothy Semenow received her PhD Fo", Caltech i1l ]955, Other tvO"'''' followed. The worlel did not end. 0 With Gordon Moore (PhD '54), chair of the Board of Trustees, Tom Everhart brings up the rear of his last Commencement academic procession as president of Cal tech.

1997 ENGINEERING & SCIENCE N O. 9 MELTING THE MANTLE

Earth's mantle reaches a olivine is known by the fo r­ exci ting that we can measure maximum remperacuce of mula (Mg,Fe),SiO" and is phase transitions at these 4,300K, say a group of a semiprecious translucent ultra-high pressures." Cal tech researchers. green gem. At vety high The researchers further Accord iog to Tom Ahrens pressures, olivine breaks note that the temperature of (MS '58), [he W. M. Keck down into magnesiowUstite 4,300K would allow parci al Foundation Professor of Earth and a mineral wi th the melting in the lowest 40 Sciences and Environmental perovskite structure. To­ kilometers or so of the lower Engineering, and graduate gether these two minerals are mantle. This agrees well student Kathleen Holland, thought co make up [he bulk with seismic analysis of wave the res ults are important for of the materials in the lower forms conducced in 1996 by setting very reliable bounds mantle. Professor of Geophysics on the temperature of Earrh's The researchers achieved Donald Heimberger and interior. Scientists need co these ultra-high press ures in Edwacd Gameco (PhD '94). know very precisely the tem­ their samples by propagating Their research suggests that "We have replicated the perature at various depths in a shock wave into them, at the very lowes t reaches of order to better understand using a high-powered cannon the mantle there is a partially melting chac we th ink occurs large-scale processes, such as apparatus called a light-gas molten layer, call ed the in the deepest mantle place tecconics and volcanic gun. This gun launches Ultra-Law-Velocity Zone. acrivi ry, which involve move­ projeCtiles at speeds of up "We're getting inco of the Earth." ment of molten rock from the to 7 kilometers per second. explaining how such a thin deep interior of the Earch to Upon impact with the sam­ layer of molten rock could the sillface. ple, a strong shock wave exist at great depth," says "This nails down the maxi­ causes ultra-high pressures Ahrens. "This layer may be mum remperacure of rhe to be achieved for only about the origin layer that feeds lowermost mantle, a rocky one-half a millionth of a mantle plumes, the volcanic layer ex tending from a depth second. The researchers have edifices such as the Hawaiian of lOco 30 kilometers co a established the melting tem­ island chain and Iceland. depth of 2,900 kilometers, perature at a preSSLUe of 1. 3 "We want to understand where the molten iron core million atmospheres. This is how Earch wo[ks." D~RT begins," Ahrens says. "We the pressure at the boundary know from seismic data that of the solid lower mantle and the mantle is solid, so it has liquid outer core. to be at a lower remperature "We have replicated the than the melting temperature melting whi ch we think of the materials that make occurs in the deepest mantle it up." of [he Earch," says Holl and. In effect, the research "This study shows that es tablishes the melting material in the deep mantle temperature of the high­ can melt at a much lower pressure form of the crystal temperature than had been olivine. At normal pressures, previously est imated. It is

10 ENGINEERING & SCIENCE No.2 1997 The IO -F

Above: flying over campus to bid fa rewell to the historic GALCIT's 10-fooc wind tunnel, che biggest wind tunnel were four World War II-era planes: a 1-28 and fastest on the West Coast when it was finished in 1929, was ceremoniously decommissioned trainer, a 8-25 Mitchell, a C.46 Commando transport/cargo April 30, 1997. Early in its 68-year history, che plane, and a Navy SNJ version of the AT-6 Texan. wind tunnel had helped establish Southern California as the aircraft-manufacturing capital of the country; it tested most of the warplanes char helped rhe Allies win World War II; and many .....,,-,~=-,..~,.,....~ generations of Cairech students learned hands-on --.... -- " aeronautics in its g iant test section. But in recen t years the lO-foot tunnel had begun to show its age, and the venerable facility needed to make way for a smaller, more cost-efficient model, incor­ porating new technology. More than 200 wind-tuonel veterans and aviation fans attended the decommissioning, as four World War II- vintage planes buzzed the campus in salure co their birthplace. During May some w onel components, including the huge test section, were dismantled and shipped off to fest in various museums across the country; the balances, which measured the aerodynamic fo rces acting on a model in the runnel, wi ll be displayed in the Smithsonian Institution in Washington, D.C.; the test section went off to Fantasy of Flight in Polk City, Florida; and various other pieces, as well as wind tunnel models, were parceled out co the Los Angeles Co unty Museum of Air and Space, the Western Museum of Flight, and the Heritage of Eagles Museum. The resc was sold for scrap. The cavernous space occupying four srories inside Guggenheim Aeronautical Laboratory now stands almost empty, save for a few hundred cons of concrete that may be very hard to remove. The wind tunnel and the building were built simultaneously, beginning in 1926 after Robert A. Millikan persuaded che Daniel Guggenheim Fund Top right: Guggenheim Aeronautical Laboratory from the south, showing the entrance (detail for the Promotion of Aeronautics to come up with top left) to the wind tunnel, in 1929. Above : the wind tunnel staff in (ront of the newly $300,000 ($ 180,000 for building and equipment, including the wind tunnel) to build Caltech's completed test section; from left: W. Toll rnien, R. Seiferth, W. Bowen, C. Millikan. H. Bateman, aeronautics program from the ground up. T. von Karman, A. Klein, F. Wattendorf, E. Sechler, W. Oswald, F. Mcfadden, and F. Moyers. (GALCIT is shott for Graduate Aeronautical

1997 E NGINEERING & SCIENCE No.2 II At left is one of the two concrete entrance cones, which neck down the air

flow from a 20~foot

diameter into the 10~foot test section, as it was installed in 1929. Unfor­ tunately, they were built so solidly that they have created a massive removal problem in 1997. They're still there (far left).

Laboratories of the California Institute of Technol­ ogy, but originally the G stood for Guggenheim.) Millikan also lured Theodore von Karman, probably the most distinguished aeronautics professor in the world, from Germany to Southern California to lead the new program. He remained director of GAL CIT until 1949, and was followed by Clark Millikan (1949-66), Hans Liepmann (1972- 85), and the current director, Hans Hornung. Although von Karman didn't settle . here permanently until 1930, he helped design the wind tunnel while on an exploratory lecturing expedition in 1926. It occupied most of the core of the new build­ ing-a space 46 feet tall, 100 feet long, and 25 feet wide. Powered by an electric 750-horsepower World War I submarine moror, its propellers created wind velocities of up to 200 mph. And yes, the propeller blades have on very rare occasions been flung loose. Jerry Landry, the current mana­ ger of the wind tunnel, remembers such an occa­ sion in 1962 when the hub fa iled, "'allowing various pieces of hub and blades ro seek new rest­ ing places." The result registered as a small earth­ quake on the Seismological Lab's instruments. From the beginning, the wind runnel was expected to do double duty as a teaching and research facility- including commercial research. Northrop's six-passenger Alpha in December 1930 was the fi rst airplane tested--of more thari 1.100 commercial tests. Besides Northrop. numerous other aircraft companies used the tunnel during the thirties, including Boeing, Lockheed, Hughes, and Douglas. The Douglas DC-I, -2, and -3 (and eventually all of them up co the DC-lO) were Above: Clark Mill ikan with a model of the DC~3 in 1935. The planes were suspended upside down for testing in the wind tunnel; the balances that weighed the aerodynamic loads are above. Right: (from left) the first aircraft tested in the tunnel, the Northrop Alpha (1930); an early version of the 8-17 (1935); and the P-38 (1937).

12 EKGINEHING & HIEN(E NO. 199 7 Left: The General Motors Stingray coupe was tested in the wind tunnel in 1959 (it came on the market in 1963).

tested here, but it was during World War II that the 10-foot wind tunnel performed its most valuable service. From 1930 on, students we re employed on a part-time basis to man the wind tunnel (and gain , , practical experience), but during the war, the staff expanded to as many as 60 (i n addition to military _~ A personnel in aeronautics training), as the tunnel .... :~ was kept running for three shi fts a day, seven days a wee k, to help develop military aircraft, Most of the warplanes that played such a crucial role in the Allied victory spent a portion of their infancy as models at Cal tech-from the P-38 Li ghtning and the p-51 Mustang ro the B-1 7 and B-29. In 1941 the original wire rigging was replaced by a sus­ pension system of rods and li nks, which allowed for quicker model changes-and so lved the prob­ lem of planes flying loose from the wires and crashing at the end of the tunnel. (The original work sec tion, made of two-i nch redwood, was also replaced at this time by one made of steel and Above: (top) the Spruce wood paneling.) The suspension system survived Goose (1944), inverted, till 1987, when it succumbed to the W hittier t hat is, right side up; Narrows earthquake, putting the lO-foot tunnel (bottom) an early jet Out of the aircraft busi ness. But there was still a steady diet of structures and aircraft, the Curtiss ~ Wright surface vehicles to keep the wind runnel busy­ XP~87 (1947). The more antennas, oil-drilling platforms, airport rowers, substantial suspension stadiums, street lighting, supertankers, as well as system replaced the wire hwnan subjects such as bicycl ists, skiers, an Olym­ pic luge rider, and current di rector Hornung dem­ rigging (opposite page) onstrating the wind speed of Hurricane Hugo for in 1941. Nightline. And of course automobil es- from land­ Top: Some of the wind tunnel's old timers take a last look speed tecord holders (E&S, J anuary 1982 and No. inside the test section during the day-long decommission­ 1, 1997) to more common veh icles. General Mo­ ing ceremonies in April. tors tested its ea rly Corvette here in 195 3, and more recently the wind tunnel has hosted the likes Bottom: Hoisted out of Guggenheim by crane, the 1941 - of the new EV-l and its predecessors-che Impact vintage test section, diffuser, and a portion of the and the solat Suntaycer (E&S, Wintet 1988). The contraction await transportation to Florida's Fantasy of last test---of a portable helicopter hangar-was Flight. conducted in February 1997. Then a bit of history was carted off to the museums. I I - JD

1997 ENG I NEERING & SCIENU NO. " We live amid a swarm of Radar Observations of Earth­ Approaching Asteroids by Steven J. Ostra

As parr of rheir opposirion to rhe Comprehen­ These are scientifically very precious stones­ sive Test Ban treaty, the Chinese have declared more so than d iamonds!-and taking samples that they would like to hold on to their nuclear of them , unaltered by a fiery passage through our

weapons JUSt in case they have (0 blow up an atmosphere, would tell us a great deal about the approaching asteroid. Are they playing politics? evolution of our solar system. In particular, one Or are they acti ng am of a socieml memory of a type of asteroid-the carbonaceous chondrites­ day in the year 1490 when, according to records fo rmed by condensation 4.5 billion years ago when from the Ming dynasty, s(Ones fell from the sky the solar system did, and they're made out of the and killed thousands of people? Are k iller aster­ same stuff that went on to form the sun, the plan­ oids finally getting some respect? ets, and us. They're called "carbonaceous" because We call these objects Earth-crossing asreroids. up to 6 percent of their weight is complex organic The main asteroid belt lies between Mars and compounds, including amino acids and nitroge­ J upiter, but the Earth-crossers travel in orbits that nous bases, which are the building blocks of pro­ cross thar of our own planet and occasionally col­ teinsl DNA, and RNA. At the other extreme, lide with Earth itself. At that point they become some asteroids come from planetary bodies that

The 70-meter Goldstone meteors 1 and, if they don't burn up in the atmo­ had already condensed, but later melted from antenna is part of the Jet sphere on the way down, meteorites. The first the heat of radioactive elements decaying within Earth-crosser was discovered in 1918 by Max Wolf them. Then, as they cooled , the denser stuff sank Propulsion Laboratory's in Heidelberg l Germany. We now know of a few and the lighter stuff floated, creating a core­ Deep Space Networl<, hundred, most of which have been discovered mantle-crust structure just like Earth's. Some which also includes sites during the past decade. By looking at the size time later, they were blown to smithereens in near Madl'id, Spain, and distribution of craters on the moon, we think we violent collisions with other large asteroids. know what the undiscovered population of these The fragments from the crust and mantle are now Canberra, Australia. The bodies looks like. (The cfatering record also shows stony asteroids, while the fragments from the core three locations al'e that the impact rate hasn't changed dramatically are metallic ones. These objects are actually sam­ approximately 120 degrees over the last 3 billion years, which implies that ples of the insides of small planets, from which we apart, so a spacecraft is as Earrh-crossers hit us and are thus removed from can decipher their histories. circulation, the pool is replenished at an equal As well as being scientifically valuable, these always within view of one rate, presumably mostly from the main belt.) We rocks are potentially a minable resource. The of them. When the believe that there are about 2,000 Earth-crossers at metallic ones are solid hunks of nickel-in;m alloy Goldstone antenna isn 't least as large as a kilometer, which turns Out to be that contain 10 parts per m illion of platinum and onc part per million of gold. And many of them busy talking to spacecraft, an important size. Two thousand is a lot-if you drove far from Los Angeles on a perfectly clearl are unbelievably easy to get to. We dream of it's also used fol' radar moonless night, you could see about 2,000 smrs colonizing the solar system, but the cost of a space astronomy. Cal tech with your naked eyes. The number of smaller mission, regardless of whether there are people on manages JPL for NASA. Earrh-crossers is much larger- there are some board or just robots, depends on how much orbital 100,000 waiting (0 be discovered that are Jarger velocity change you have to introduce to get from than the Rose Bowl, and about 70 or 80 million Earth to your destination and back. Since Earth­ larger than a typical tract house. We live amid a crossing asteroids come so close, a properly timed swarm of small wotlds whose existence was unsus­ launch could essentially just step over to them. pected a century ago, and whose abundances have For economic reasons alone, these are the objects been realized only during the past few decades. we're going to colonize firs t, after the moon.

19 9 7 ENGINEfRlNG & SCIEN{E NO. IS Left: The orbits of 33 Earth-crossing asteroids. The main asteroid belt is shaded yellow. Right: Every now and then, an Earth-crosser becomes an Earth-hitter. Each of the I S6 dots on this map marks an impact crater. Many more, obscured by _"i:' vegetation and erosion, .. : " wait to be discovered. Map courtesy of R. A. F. Grieve, Geological Survey of Canada.

But even if we never go [Q these objects, even­ tually it is inevitable-absolutely inevitable-that they will come to us. The surface of the moon is covered with craters made by asteroid and comet hits. The surface of the Earth doesn 't have as An asteroid hits ar about 20 k ilometers per many craters, even though it has suffered the second-a velocity well beyond human experience. same violent history, only because ours is an active planet. Plate tectonics, volcanism, weather, ero­ sion, and so forth have erased the tecord of long­ ago collisions. But we're still finding the scars, as the little dots on the above map of the world show. When an asteroid hits the Earth, the damage it does depends on how big it is, as shown in the diagram at left. An asteroid hits at about 20 kilometers per second- a velocity well beyond human experience-and all its kinetic energy The damage an Earth­ ,. is released upon impact, The amount of kinetic crosser does when it hits ;:: 101 .! energy depends upon the asteroid's mass, and us depends on its energy , ,. hence its size . We measure the energy release in release, which in turn f ,. megacons, where one megaton (4.2 X IO u joules) & 101 is the energy equivalent of detonating a million depends on its size, both j ,. tons of TNT all at once. The atomic bomb of which are plotted ,. dropped on Hiroshima was a mere 15 kilotons, a logarithmically on the ,. ,. ,. ,. number so tiny that it's way over on the left of the horizontal axes. "Size" is diagram. As we move across the diagram from left to right, at first the objects are toO small even to only roughly equivalent to make it through the atmosphere . These meteors diameter, as many of these Aslorokl DIomot .. do no damage-their energy release JUSt powers _. 'm ,~ ,- .~ 'M ,- objects have irregular (or a light show. But soon the penetration threshold ,- ..... -- - unknown) shapes. The is crossed; slightly larger ones deposit mos[ of their kinetic energy on O[ near the planet's surface penetration threshold -. and devastate larger and larger areas. Should the j ~ ' "" ,- " (shaded) is really more of a } Mllleflium impact leave a crater, it wi ll be 10-20 times the asteroid's size. Then, at a diameter of about a kilo­ transition zone than a ~, meter, we cross a global threshold. Ir no longer sharp threshold. The KIT I ,., matters where an object hits-it will kick so impact is widely believed ,., ". ..•... much dust up into the upper atmosphere that to have killed the ,., m_ the sun will be blotted out worldwide for several ,., "'11: dinosaurs. After Chapman ." , ,. ,. ". ,. yeats, making agriculture impossible and leading 1Mg.wn1 TNT ~hr.""I_ to the starvation of roughly a quarter of the people and Morrison, 1994. on the planet. This is a civilization-ending aster­ oid. At much higher energies-lO-kilometer

,. ENGINEERING & SCI EN(E NO. 1997 several ongoing asteroid searches, but they haven't gOt the resources to be exhaustive. For less than $5 million a year over a 10-year period, we could find more than 90 percent of the kilometer- and larger-sized asteroids. It seems to us very cost­ effective risk reduction-very good insurance­ Kilometer-sized, civilization-ending impacts happen on average once every logical in the same way that life insurance, or fire insurance, or car insurance is logical. NASA's 100,000 years, so the probability that we face one during the next century annual budget is $14 billion a year, so we're completely perplexed as to why NASA does is roughly one in a thousand. "not recommend this program .... " If you feel that such a program would be sensible, tell your congressperson. If we did find a threatening object, what would we do? With currene technology, if we had enough warning, we could set off a nuclear warhead near the asteroid, nudging its orbit so that it would miss the Earth. However, until we discover such an object, most of us feel that devel­ oping a deflection system would be too costly to objects-we cross another threshold where the warrant our actually doing so; also, if we had a devastation is so horrendous that most of the life standby deflection system and actually started to on Earth is eliminated. The most popular mass­ experiment with orbit modifications, the system extinction event was 65 million years ago, of might be accidentally used or even intentionally course, when not just the dinosaurs but some 75 misused to deflect a harmless asteroid intO a percent of the species on the planet were wiped collision course with Earth-an idea that is very out, but there are other such events in the paleon­ popular with some people who write comic books tological record. or design video games. With somewhat more­ So how often do these collisions happen? The advanced technology, we could travel out to the very, very low-energy events-the Hiroshimas­ asteroid and attach a solar sail or some sort of happen maybe once a year. But you hardly ever rocket engine to push it away from us. Everything hear about them, because they leave no trace on would depend on how much warning we might the ground and they generally occur over unpopu­ have. The odds are that we would have enormous lated areas or the ocean, where their fireworks go warning-maybe centuries-but not if we don't unappreciated. Impacts like the Tunguska event, start looking. which happened in Siberia in 1908 and released Coincidentally, on May 19, 1996, an asteroid 15 megatons of energy but left no crater, happen designated 1996JA1, which had been discoveted once every several centuries. The Tunguska aster­ only three days earlier, passed within a haif's oid was about 60 meters across, and it released as bteadth of Eatth-{lfily slightly outside the otbit much energy as a magnitude 8 earthquake. This of the moon. Less than a week later, on May 25, is at the low end, in terms of the number of people asteroid 1996JG (discoveted on May 8) whizzed who could be killed by an asteroid impact. As we by us at eight times the distance to the moon. approach the global threshold, we suddenly get to Both bodies are only a few hundred meters across, the point-because the effects are global-where so they could not have produced global catastro­ the number of fatalities skyrockets. And, finally, phes had they hit us. But if they had landed in mass-extinction events are very rare---once every the ocean (71 percent of Earth's surface is ocean), 100 million years, on average. they might have raised tsunamis that could have Kilometer-sized, civilization-ending impacts wiped out the coastlines of the adjacent conti­ happen on average once every 100,000 years, so nents. Up to 1 percent of the global population the probability tbat we face one during the next would have been killed by such an impact: century is roughly one in a thousand. Those Those two asteroids missed us this time, but odds are extremely low-however, the conse­ where are they going to be in the future? Unfor­ quences are extremely horrible. That fact alone tunately, with just optical measurements, it's hard suggests that it's worth finding all the kilometer­ to predict a newly discovered asteroid's orbit for, sized objects and determining their orbits, just say, the next century. What matters is the uncer­ in case we're unlucky. tainty. It's one thing to sayan asteroid is going This would be very easy to do. Asteroids are to pass one lunar distance from Earth, but quite discovered with wide-field cameras that take time­ another to say that the asteroid is going to come exposures of the sky. The camera pivots to follow within one lunar distance plus or minus 21 lunar the stars, so that they appear as points in the distances. That's very uncomfortable. But if we image. But asteroids, which are moving with use radar observations, there's very little uncer­ respect to the stars, show up as streaks. There are tainty left. Donald Yeomans, Paul Chodas, and

1997 ENGIHEERING & SCIENce No.2 17 PloOfO by D.lvid Parl«.-r, 1997ISci~na 1'bolO libntry

We can g et IO- meter resolution, which is about

the length of a school bus, and we can m easure

veloci ties of one- tenth of a mill imeter per second,

which is rhe speed of rhe tip of rhe minute hand on

a kitchen clock,

J on Giorgini of Jpr:s Solar Sysrem Dynamics with an asteroid named Castalia, using data we Group can use our radar data to work up an orbit got fro m Arecibo within twO weeks of the aster­ that's good for 100 years or more. We would oid's discovery (by Jpr:s Eleanor Helin at Caltech's immediately know whether we're safe or not. Palomar Observatory) in August 1989. (Castalia We study these asteroids with either of twO very was named for a nymph who, while fl eeing the The radio dish at Arecibo large antennas. One is the 70-meter Goldstone amorous attentions of the god Apollo, dived head­ antenna, about a three-hour drive from Pasadena. long into Mount Parnassus. Instead of making a was carved out of a natural Goldstone is part of the Jet Propulsion Labora­ crater, she left the spring that bears her name.) "punch bowl," or sinkhole, tory's Deep Space Network, so the antenna is Because Castalia was quite close to Earth at the in the limestone karst used primarily for talking to spacecraft, but up time-a mere 11 lunar distances away-this was region of northwestern to 4 percent of its time is devoted ro radar astron­ also the first-ever set of delay-Doppler data with omy. The other is the largesr radio telescope in suffi cient echo strength and resolution to recon­ Puerto Rico. The tele- rhe world, the 305-merer (I,OOO- foo t) Areci bo struCt a shape. (We have since done this with scope is aimed by moving telescope in Puerto Rico. The twO instruments are objects at greater distances.) The resolution the antenna feed system, complementary. The Arecibo telescope is not fuUy is pretty poor, but the important finding is that steerable (Goldstone is), but it's 30 times more Castalia is a double asteroid-a co ntact-binary which hangs from rails on sensitive. But it also has been used for radar only a support structure that is 4 percent of the time. itself suspended over the When we bounce a radar pulse off an asteroid, .... ~ we measure the time it takes the echo to return, ~ .'- dish from three towers. ..,., which tells us how far away the asteroid is, and ... The telescope can see a .. .. the echo's Doppler shift, which tells us how fast cone of sky 40 degrees in the asteroid is movi ng, (Objects moving toward fjii1-- or diameter and centered on us compress the echo to highet frequencies; teced­ 'W ' 'W.., ing objects stretch it out to lower ones.) For an the zenith. The Arecibo .. asteroid about 20 lunar distances from Earch , we .- Observatory is part of the can get lO-meter resolution, which is about the National Astronomy and length of a school bus, and we can measure ~., Ionosphere Center, which is velocities of one-tenth of a millimeter per second , ...... ," which is the speed of the tip of the minute hand .. operated by Cornell on a kitchen clock. That's why radar is so power­ RCl'fimed wilh .,...miuioo from R. S. Hudsoo and S.). Oslro, -Sha.,.. of A & t~roid 4769 University under a ful in refining orbits. ea.",lia (1989 PB) from l"v~[Sion of Radar imag"',- Sci,ru., yolume 263, pp. 940-943, 1994. Copyrigbl 1994 by ,he American Association ror th ~ Advan ce m~m o f Scieoc~. cooperative agreement But wait-there's more! Asteroids appear only as points of light in even the best telescope with the National Science Castalia as modeled by the Hudson inversion looks rather photo--they're just too darn small. But radar ca n Foundation. pick our surface features. A Cal tech grad who's like two biscuits that sat too close together in the oven now at Washington State University, R. Scott and fused. The lobes are roughly 0.8 and 0.9 kilometers in Hudso n [BS '85, PhD '91), developed a technique diameter; at 100 meters or more deep, the cleft between to generate a three-dimensional model of an as ter­ them could swallow a 27-story building. The dimples on oid from a sequence of radar observations, and from this model we can make images that look the model might be craters. The asteroid is seen rotating like photographs. We tried this for the first time through 220 degrees in 20-degree increments.

,. ENGINEERING & SCl lN(E NO. 199 7 "Seeing" Shapes with Radar

- ~ I I ",0 ,I • .0" in the previous picture are " " • side turning away from Earth wi ll shift the echo co lower ftequencies.) Thus, a radar image plots the the three-dimensional ~ ,. 3 • 0 equivalent of this echo's brightness versus its delay time on the ver­ , tica l axis and brightness versus frequency on the shaded bar. Q • • • • horizontal axis to generate what's called a delay­ Bottom: This delay-Doppler Doppler image. In effect, the asteroid has been

"movie" of Castalia con- :> 0> ,. sliced along twO perpendicular planes like a potato • .. I - " being sliced imo French fries. And that's one rea­ sists of 64 images made .., son why these plots don't look exactly like the over 2.S hou rs. The "> .. , -, . , " " asteroid---each point in the image comains the images read from left to _. reflection from borh ends of each French fry. A right, top to bottom. The , , o · • , . I • point may even contain more than two reflections, -. if that particular French fry passes cllCOUgh the colors from blue to red side walls of a crater, or a cleft on the asteroid's , .) 0 ". 0' ~~ l~ represent increasing ," surface! 1r rakes a mathematical analysis, using intensity. Scott Hudson's techniques, of a sequence of delay­ • • I'" , ~ • , • .? • Doppler images to resolve the ambiguities and reconstruct the asteroid's acruai shape.'CJ

1997 ENGINEERING & SCIENCE NO. 19 asteroid, the first ever seen. Such a thing could form only if the tWO lobes mated at a very gentle relative velocity, so that they didn't pulverize each other. Perhaps it formed out of the wreckage of a much larger asteroid. If two shards went sailing out along a common trajecrory dose enough to each other, they might stay gravitationally bound. The tWO lobes could even be physically touching each other, but in no way "cemented" together. The discovery that contact binaries exist has implications for interpreting the cratering record elsewhere in the solar system, and also for defend­ ing ourselves from such objects. If we blew up a nuclear bomb closer to one lobe than the other we would shatter the nearer lobe but leave the ' other one completely intact and the asteroid's

R~ p ri nlnl wilb ~rmilSion from R. S. H udso~ and S. J. 0",0, · Sba~ and Non. Princi(lQo1 Axis Spin Sme of A SI ~ roid 41 79 Tou r. ris: course unaltered. S(JmrI, yolu me 270, pp. 84-86, 199'. Copynght 199' by {he American ~ialio n {or {~ A d Ylnc~ment ofScienc~ . Thre years after the Castalia observations, in December 1992, we did a thtee-week-Iong experi­

ment on another object, called Toutatis. ToutatisJ by the way, is one of the most accessible as teroids. Toutatis as seen at six­ Its orbital plane is almost identical to Earth's; it's hour intervals over the an excellent candidate to collide wi th us sometime during the next several million years. In fact, week beginning at 10:00 that's how it gOt its name. Irs discoverers, a.m. Pasadena time on Christian Poll as, Alain Maury, and their colleagues December 3, 1992. at the Cote d'Azur Observatory, are fans of the Although the long axis has Asterix and Obelix comics. Those ancient Gauls swear by the god Toutatis, and the only thing they essentially returned to its fear is that someday the sky will fall on their original orientation by the heads. Toutatis won't quite fall on our heads in ' end or the sequence, the the year 2004, but it will miss us by a mere four lunar distances, coming dose enough to be visible asteroid's orientation through binoculars. At that point, Earth will be Naming an Asteroid around that axis is not the as large in Touratis's sky as the moon is as seen same-the lobe that was from the Earth. Above left are stills from our three-dimensional When an (optical!) astronomer discovers an pointing downward in the model of Toutatis. It's a much higher-resolution object, the sighting is reporred to the Minor first image is now sticking model than the one of Castalia, and represents an Planet Center at Harvard, which gives it a out toward us. The scale even stranger world. From some orientations it provisional designation (e.g., 1989 AC). looks like a single object. From others, it looks Many aStronomers may then observe the aster­ bar in the lower right like it has two parts. From still orhers, it looks oid, making rhe measurements needed to refine corner is one kilometer like it has three. Geologically, we're at a loss to the orbit. When Brian Marsden of the Minor long. Data are from explain this- we know that collisions were Planet Center considers the orbit secure, he Goldstone and Arecibo, involved, but we don't know exactly how. But gives the asteroid a number (e.g., 4 179) and the strangest aspect ofToutatis is its rotation. then the discoverer(s) can name it (e.g., It doesn't spin around a single axis, but rumbles Touratis). Marsden considers an orbit secure in a manner radically unlike anything else in the when the object is seen again, on a subsequent solar system that we know of. Toutatis rotates approach to Earth, in the location and at the around its long axis once every 5.41 days. ·Mean­ time predicted by that orbit. In some cases, while, this axis is precessing around a direction the object proves to be one that had been seen fixed in space-Toutaris's angular-momentum earlier, but then had been lost before enough vecror-once every 7.35 days. These are non­ observations could be made to pin down its commensurate numbers, which means that orbit. Marsden then decides which "discovery" Toutatis's orientation in space never repeats. countS, i.~ .• who gets naming rights. In There is no truly periodic pattern. How it got Toutatis's case, 1989 AC proved to be 1934 CT, into this rotation, we don'r know. It had to be which had been seen twice by Eugene Delporte a collision, but we don't know what kind of in Uccle, Belgium in 1934; the discovery collision. We do know that it would be a spec­ belongs to the 1989 discoverers, whose data tacular experience to land on Touratis and watch permitted the orbit to be traced backward the sky. Imagine trying to navigate by using the thtough half a century. 0 stars-the "Pole Star" would change daily! Earth

2. EN GINEERING & SCIENCE NO. 1997 R ~printed with p"rmi«ion from S.). as(ro c( aI., "IiKI< ~ m ~ donga(ion of a.t~ roid 1620 GNlgraphos from radar images: N"llm, volum ~ 375, pp. 474- 4n, 1995. Copyright 1995 hy Macmillan Mag01.in .. Ltd.

Above: A 6,OOO ~ ton rock hitting Castalia at the compara­ tively gentle velocity of five kilometers per second has 20 has a fixed north star-fixed on the time scale of percent more force than the Hiroshima bomb. In this set someone reading this, at any rate-because of exterior and cutaway views at one-tenth of a second Earth's rotational axis precesses only once every after impact, the top row shows damage ranging from 26,000 years , but Toutatis's rotation and preces­ I sion rates are comparable to each other. minor (blue) to pulverization (red). The red fingers are At left is Geographos, which is about 5.1 actually hairline fissures-given infinite computing power, kilometers long by 1.8 kilometers wide. It was you'd eventually see these fractures opening up and pieces discovered in 1951 by Albert Wilson [MS '42, PhD '47] and Rudolph Minkowski as part of rhe coming apart near the impact zone. The bottom row Palomar Observatory Sky Survey, which photo­ shows particle velocity (on a logarithmic scale where blue graphed the entire Northern Hemisphere sky over is 0.1 , green is 1.0, and red is 20 centimeters per second) several years. The survey was sponsored by the as the pressure wave propagates through the interior. National Geographic Society, hence the asteroid's name. We don't have a 3-D model of this one yet, Castalia is assumed to be a homogenous, basaltic body. Geographos, as seen from but the radar images, processed by Keith Rosema Below: Although the crater itself takes much longer to above. The central bright [BS '89] at lPL, are good enough for us to see form, the impact fragmentation is all over in three-tenths square marks the north some unusual features. Geographos is parameci­ of a second. The impact severely damages Castalia, but um-shaped- the most elongated body yet discov­ pole, and Geographos is ered. But to my eye the strangest of its features does not blow it apart or appreciably alter its trajectory. spinning clockwise in the are the knobs on each end. Their leading edges plane of the page. The (with respect to Geographos's rotation) are convex radius of curvature of the and their trailing edges are slightly concave, g iv­ ing Geographos's ends a sort of pinwheel look. knobs on either tip of the How did these form? And how can they survive, asteroid is only a few given the constant bombardment they m ust hundred meters; then undergo from other asteroids? Perhaps it has to beyond the gentle do with the asteroid's low gravity, long shape, and rapid, five-hour rotation. The centrifugal force at concavity that defines the Geographos's tips might be just about equal to its knob, the trailing edges g ravitational pull, and the asteroid is almost able are nearly linear for a to fling the material off. When we finish the 3-D experiments. In the frames from an animation by modeling, we can do computational experiments lPL's Eric De long and Shigecu Suzuki (above), kilometer. to test hypotheses about how these protuberances an eight-meter, 6,ODD-ton rock (a small asteroid) The tick marks along the formed. crashes into Castalia. A spray of particles is picture's right edge are Once we have three-dimensional models, ejected, and a shock consisting of a compressional one kilom-eter apart. The we can use them as targets in physically realistic wave followed by a smaller extensional wave (not computer simulations of impacts. Collisions are shown) rips through the body. Exactly what hap­ data were taken at terribly important, and we need to understand pens depends on both Castalia's physical properties Goldstone in August, 1994. their effects if we are to learn how asteroids and its collisional history, because every impact evolve. Erik Asphaug of NASAl Ames has run affects the asteroid's integrity and the way it such simulations, based on our model of Castalia's responds to impact stress. Even this relatively shape and rock properties derived from laboratory small cratering event causes widespread internal

1997 E HGI HEER I NG & SCIENCE No.2 11 consolidated bodies don't propagate stress waves well. A nearby nuclear detonation would basically be "soaked up" by such an asteroid, shattering it into finer pieces instead of pushing it off course. This is a problem , because the overwhelming odds are that any asteroid that could threaten Earth has itself been hit at some time in the past by some­ thing larger than eight meters in diameter. and therefore is probably already fragmented. We also want to understand the dynam ics Ir could bring a whole new dimension to parenting. If yOUT child's of orbits that are very close to small, irregularly shaped, rotating asteroids. Some ejecta will be been bad, instead of "Go to your room! " you could say, "OK, YOll go thrown off tOO slowly to escape from tbe asteroid. into orbit for a while." Daniel Sc heeres of ]PL has found that the geom­ etry of return orbits-orbits that eventually return to the asteroid's surface, or the equivalent of a bal­ listic trajectOry on Earth-is very peculiar. The top row of ill us trations below shows what you would see if you were standing on Castalia and weren't awa re that the asteroid was rotating­ fraccuring. Escape velocity on Castalia is about what we call a Castalia-fixed frame of reference­ one meter per second, but most of the rock we and you threw up a rock that left a trai l. It wan­ pulverized in this simulation attained velocities of ders all over the sky and, depending on where you onl y a few centimeters per second and so remains stood, which way you were facing, and how hard gravi tationally bound together. It's quite d ifferent you threw the rock. you'd get a completely differ­ from what we're used to on Earth. where the self­ ent orbit. This is a realm of geometric complexity gravity between, say, the pieces of a broken saucer that we never appreciated before. If you stood off are negligible. from Castalia and watched it rotate beneath you­ We want to understand the effects of collisions a star-fixed reference frame~the orbit would now not JUSt to make sense of the physical properties be almost planar, but the trajectOry would still go we observe-to connect what we've learned from through a bunch of strange gyrations in space meteorite samples with what we can learn about before returning to the asteroid. And finally, of asteroidal composition through ground-based course, if you threw the rock a little tOO hard, it telescopes- but also to look ahead to the day could whirl around Castalia for several passes be­ when we might have to nuke one of these objects fore escaping and going into orbit around the sun. in self-defense. What thi s and mher simulations These calculations also apply to human and have taught us is that it might be much easier to spacecraft operations in the vicini ty of a small curn an asteroid into a flying rubble pile than to asteroid. Imagine what it would be like to play alter its trajectory by more than one or two centi­ baseball on Castalia-you'd have to have a lot of meters per second. To make matters worse, loosely patience and do a lot of practic ing. If you went

A return orbit around Castalia, seen simultaneously in a Castalia-fixed reference frame (above) and a star-fixed reference frame (below) . Although the reference frame is fixed in each set of images, the point of view sometimes moves in order to highlight some aspect-the planar nature of the orbit in the star-fixed reference frame, for example. The entire orbit takes 16.9 hours to complete.

22 EN GI NEER ING & HIEHCE NO. 1997 deserving of that moment in history, such as send­ ing a human being to an Earth-crossing as teroid and really beginning the manned exploration of the solar system. Of course, such an underraking would be very expensive and isn't li kely to happen by that time. Meanwhile, we'll continue explor­ ing with radar. And if we could fund a serious optical search for these objects, we'd starr discover­ ing them in huge numbers, and eventually we'd get to the point where almost once a week--cer­ tainly once a month- we could have an encounter via radar with a new Earth-crossing asteroid. We could put it on our World Wide Web site (http:// echo.jpl.nasa.govl), so that anybody with a com­ puter could witness the first radar imaging of the object and see the radar movies and eventuall y the three-dimensional models. With a three-dimen­ sional model, you could make virtual visits to the asteroid, putting yourself into orbit around it and trying to land on it. People love to explore out for a walk, and were feeling in good spirits and strange, exotic places-if you could caU your trav­ jumped up, you might go into an orbit that would el agent and book a cruise to Castalia or Touratis take you around the asteroid for days! If you were tomorrow, I'm sure it would sell out. In a few roo light on your feet, or unlucky, you might never years, with high-definition TV and high-resolu­ come back. And parents like to toss their little tion computer models, you could almost vacation kids up into the air and say "Wheeee!" They'd there. You could walk around, playa little catch, have to be really careful about that on Castalia. even hit golf balls into orbit. Our models are the But it could bring a whole new dimension to first step toward that experience, and it's going parenting. If your child's been bad, instead of to be how most of us will explore these worlds. "Go to your room!" you could say, "OK, you go Sooner or later the survival of human civilization into orbit for a while." will depend on how intimately we know these As I mentioned before, Touratis has a weird, near neighbors of ours, but in the meantime, it tumbling rotation like a football during a botched would be possible to make a first-time encounter Above, right: This return pass. Consequently, orbits around Toutatis are with a fantastic new world part of the regular orbit around Toutatis, very different from orbits around Castalia. On experience of everybody on the planet who's shown in a star-fixed frame Castalia, in a star-fixed frame, the return orbir I connected to the Internet. That's my personal of reference, takes 2.9 days showed you had a strange shape, but at least scayed millennial vision. 0 nearly planar. Not so on Toutatis, where return to complete. orbits can form cocoons around it. There are some Above: This family of four orbits that circle hundreds of times before eventu­ "geosynchronous" orbits­ ally making it back to the surface. Above is a star­ fixed view of a shorter return orbit. in which a satellite appears Surprisingly, it is possible to have periodic to hang at a fixed point in orbits around Toutatis. In a star-fixed frame, you Steven J. Ostro earned a BS in ceramic science and an the heavens, as seen from would see a satellite in one of the simplest of these AB in liberal arts from Rutgers in 1969. He went on the orbited body's orbits moving along a nearly elliptical path, juSt to Cornell for a master's degree in engineering physics in like it would around Earth. But if you were stand­ 1974, and earned a PhD from MIT in planetary surface-instead trace out ing on Toutatis, you'd see something completely sciences in 1978. He then returned to CornellJ joining figure-eights in the sky different. For example, a satell ite in what would the astronomy department as an assistant professor. He over Toutatis. From a star- be a geosynchronous orbit around Earth would arrived at)P L in 1984, where he now holds the title trace a giant figure-eight over the surface of fixed point of view, the of senior research scientistJ is the Goldstone Solar-System Toutatis. And some orbits close to rotating Radar project scientistJ is a member of the science team four satellites would be asteroids are highly unstable, which is of concern for the Titan radar-mapping experiment on the Cassini spaced 90 degrees apart in to the NASA engineers flying the NEAR (Near­ mission to SaturnJ andJ in his spare time, teaches a a roughly circular orbit Earth Asteroid Rendezvous) spacecraft toward graduate course at Caltech. The leading authority on Eros, a large Mars-crossing asteroid. If they pick the radar propertier of asteroids, the Jalel/iter of Mars around Toutatis. the wrong orbit, NEAR will collide with Eros or andJupiter, and SaturnJs rings, Ostro has been a escape from it. NEAR was lau nched on February ({regular" at Arecibo and Goldstone for two decades, 17, 1996, and should rendezvous with Eros in late and has bagged 80 near-earth and 'main-helt asteroids. January or early February 1999. He was also one ofseven astronomers to play key roles We're approaching the turn of the millennium. in three NASA workshops on detecting and intercepting I think it would be wonderful to have an event Earth-crossing asteroids.

1997 ENGINEERING & HIENCE No.2 Our brains have to make hypotheses about what we think is our there in the

real world. We hope that these hypotheses are right,

because a mistake could be fatal.

14 ENGINEERIHG & SCIE NCE NO. 1997 How We See by Richard A. Andersen

When we look around us, seeing is so effortless that we think we naturally perceive what is accually out there in the world. But, in face, the brain works very hard at reconstructing its own reality- what we refer to as neural representation. In the well-known Kanizsa triangle shown above, you can see illusory contours that are created by the occlus ions, rhe Lines, and the litcle Pac-Man figures. These "contours," and the perceived variations in bright­ ness lie entirely within your brain and do nor exist in the real physical world. Because the brain is often faced with an ambiguous, ill-defined environment, it's very useful to be able to reconstruct such lines. Our brains have to make hypotheses about what we think is out there in the real world. We hope that these hypotheses are right, because a mistake could be fatal. In terms· of evolutionary pressure, the brain has evolved over time to create its own reality that meshes with the world in such a way as to enable the organism to survive. Neurobiologists believe that at least a third of our approximately one hundred thousand genes are exclusively involved in brain function. With that limited number of genes, we can't completely specify all the complex connec­ tions and structure in the brain, so during some periods of development, the brain has to look to the outside world for assistance in forming its structures. At a very early age, for example, the brain becomes plastic for vision; during this critical period information from the twO eyes, which compete with each othet, is used to actually set up the appropriate neural machinery fot depth perception. Driving down a street The understanding that the visual system actually co nstructs images of reality has led to an exciting revolution not only in neuroscience but also in (as here in La Canada the field of philosophy. A new school of philosophy called neurophilosophy Flintridge, not far from has reconsidered what the nature of reality and the nature of knowledge are, Caltech). generates an based on what we now know about how the brain wotks and about the optical flow of motion changes that occur in our neural networks over the course of development. Vi sual information required to construct this representation of the. world signals. Surrounding comes in through the eyes and is projected on the retina; then the optic nerve objects seem to radiate sends this information to the thalamus, which passes it up to the primary out from the focus point, visual cortex (called VI), where simple aspects of the visual scene are first expanding toward the analyzed. Then information is projected Out to cortical areas around the primary visual cortex, and they process the visual image more elaboratd y; here edges of the field of vision. is where the more complicated cognitive functions take place. The informa­ Processing of these tion travels along two processing streams-one to the upper part of the brain complex signals occurs in and the other to the lower pan. In 1982, two neuropsychologists from che N IMH, More Mishkin and Leslie Ungerieider, proposed chac the pachway to the higher levels of the the upper pare of the brain was the "where" pathway, which tells us the brain. Photo by David location of an object. They labeled the lower route the "what" pachway, Bradley. because it seems to handle informacion about the object itself. Patiencs with

I 9 9 7 ENGIN EERING & SCIENCE NO. 2S "Where"

Left: This schematic view of a monkey brain shows the "what" and "where" pathways. Both pathways "What" begin at the back of the system brain in the primary visual cortex (VI); the "what" pathway proceeds through the visual cortex in the injuries, or lesions, co the upper pathway can iden­ lower part of the brain to tify objects and the differences between objeCts, the inferotemporal cortex but can't tell where they are. With lesions co the (IT), and the "where" lower area a person can tell where things are but can't identify them. Lesions in this area can cause pathway leads to the an interesting syndrome called prosopagnosia, in posterior parietal cortex which people can't identify faces, including their (PPC) in the upper part. own. This objeCt-based pathway is also important for the perception of color. A typical lesion in the upper, or "where," pathway might leave a patient unable co pour a liquid into a glass. He can see the glass and he knows it's a glass, but he can't figure out where the glass is with respeCt co his body. Another one of the deficits from damage co this pathway is the inability CO attend co the area of space opposite to the hemisphere that was damaged. Monkeys have visual funCtions similar to ours. They see color the way we do; they see motion and depth; they perceive objects; they make eye move­ ments in the same ways that we do. So they make ideal animal models for studying the human brain, because we can do experiments with monkeys that we obviously can't do with people. We have several rhesus monkeys who participate in experi­ ments for a period of years. Recently we have been sllccessful in placing them in zoos for their retire­ Above: A microelectrode ment. A common technique for studying the visual system introduces very fine (about the is placed near a neuron to diameter of a human hair) wire eleCtrodes into a record its electrical monkey's cerebral cortex. We park these elec­ activity (photo by Fritz trodes near nerve cells. During the experiments Goro). A recording is the monkeys are awake and performing different tasks that they've been trained co do, such as mov­ shown at right, o.n the ing their eyes coward a stimulus, reaching coward opposite page; the changes a target, or pressing a button for a juice reward. in activity are due to the In trus way the monkeys "tell" us what they see. As they do their tasks, the electrodes record the appearance and disappear­ activity of the nerve cells. Then we can correlate ance of stimuli. the activity of specific cells with the behaviors or perceptual experiences the animals have. The illustration at the bottom of the opposite

2. EilGINEER l ilG & SCIENC[ No.2 1997 To undersrand the btain and how it processes visual images, we not

only have to know what each single element is saying, but also

what the whole ensemble of activity is saying.

Above: The Rose Bowl prank of 1961 is a good example of population coding, one of the brain's strategies for processing visual information. A single perception is stored page shows the type of signal that we record on by 400 pixels, while the brain contains about a one of these electrodes. Time is plotted along the hundred billion cells. Each one of these cells can across many units, but it x-axis, while the y-axis displays the membrane change its activity over a certain range to store a only makes sense when all potential, or eleCtrical activity, coming from one small bit of rhe "picture." A simple example of the units are combined. of these nerve cells. When we shine a light or population coding can be seen in the great Rose present a srimulus to the animal, a cell that is Bowl prank of 1961, where each University of involved in the perception of that stimulus begins Washington fan knew only that he or she was to fire action potentials-pulses that are the com­ holding up a white or a dark card and, fortunately munication method for nerve cells. These signals for the Cal tech students who pulled off the prank, will then be transferred via synapses to other nerve no one person could see the whole message. When cells to which this nerve cell projects. This synap­ they all flipped their cards in unison, they inad­ tic transmission is how messages get sent through vertently spelled out CALTECH. To understand the cerebral cortex, and by tapping into this the brain and how it processes visual images, we system with our electrodes, we can determine the not only have to know what each single element locations of very specific types of visual processing is saying, bur also what the whole ensemble of that the brain uses to reconstruct reality. activity is saying together. The brain uses five basic strategies in its visual A second important feature of how the brain processing: population coding, functionallocaliza­ works is known as functional localization. This tion, parallel processing, hierarchical processing, concept refers to the fact that different parts of the and association. A single neuron in the brain cortex are specialists in particular visual processes. looks at only a small piece of the world. This At the turn of the century, a German neuroanato­ fragmentation actually starts in the retina, which mist, Korbinian Brodmann, divided the human has the image of the whole visual field on it, yet a brain into about 50 different areas simply by single cell receives its input from only a tiny part looking at sections of it under a microscope and of that image. So we have to realize that each time noticing the differences in nerve-cell structure or we record a signal from one of these nerve cells, packing density in different cortical regions. we're seeing only a small part of the entire visual With the advent of microelectrode recording message. This brings us to a concept known as techniques, neurophysiologists in the 1970s began population coding-the idea that a whole percep­ dividing the brain lip into areas based on different tion is stored across many, many units. Our brains functional activities as well. Often these func­ are a bit like TV sets; we can think of neurons as tional areas corresponded to Brodmann's anatomi­ corresponding to the pixels on the screen. Of cal ones; for example, Vi was his area 17. But course, a normal TV screen measures about 600 others, like Brodmann's area 19, turned out to contain many different cortical areas delineated by functional differences. It's also important, in dividing up the cortex, to notice that one area might connect to some areas and not to others, so that different cortical areas have specific connec­ tivities between them. About 35 different cortical areas have been identified as being involved with vision in monkeys, and there are probably even more in our own brains.

1997 ENGINEERING & SCIENCE NO. 17 which is also specialized for color. If area V4 sustains damage, the patient will have difficulty This schematic diagram perce iv ing color in the opposite visual field. illustrates the hierarchy of Another pathway-for marion processing- goes from Vl CO the "thick stripe" region ofV2, and the cortical areas involved then on to an area call ed V5 or MT (for medial in vision. rising from the temporal area, discovered by J ohn Allman, Cal­ primary visual cortex at tech's Hixon Professor of Psychobiology and professor of biology) in the visual association the bottom up to the cortex. An injury to this pathway pcoduces a very highest levels of associative specific marion deficit; a person looking at traffic, processing at the top. The for example, could see the cars, but would be "where" pathway is on the unable to see that they are moving. Each of these parallel streams is also organized left and the "what" hierarchically. Take, for example, the pathway for pathway on the right. motion that I JUSt mentioned. Cells in VI extract (From Fell eman and Van some very basic information about the direcrion of marion, which is maintained in area MT and Essen, The Cerebral shown in the record ing from an MT cell below. Cortex,Yoll , No. I, When something moves up within the ceU's 199 1. By permission of receptive field, this parcicular cell gives a small Oxford University Press.) response, bur it gives a much more vigorous response when something moves downward. This cell is giving information about the direction in which something moves, a very simple and Each one of the boxes in the diagram above basic SOft of function. But, unlike area Vi cells, (created by Dan Felleman and David Van Esse n) cells further up the hierarchy in MT also deal with corresponds to a cortical area that has a particular more complex motion clues that are important for function. The primary visual cortex is at the perceiving the three-dimensional structure of bottom, and information eventually rises to the moving objects. highest levels of processing in the association cor­ Work in my own lab has involved the upper tex, which then connects ro the mOtor cortex to reaches of the "where" pathway-the areas that do direct movements. The areas on the left corre­ the higher-level processing of location and motion. spond to the "where" pathway, and the ones on Our recent research has tested how monkeys per­ the right to the "what" pathway. ceive three-dimensional structure from an object's Of the three remaining strategies, parallel motion. If we were to paint li ttle dots on a hol­ processing divides up information and processes low, glass cylinder and view it with one eye, the it in parallel along separate lines, and hierarchi cal cylinder would look simply like a set of dots until processing transfers information from one level co we turn it; then the three-dimensional shape of the another through more and more complicated glass would immediately pop out. So motion analyses as it moves up the system. The final im­ signals can give us impressions of three-dimen­ portant concept is association- after we've broken sional shape. Instead of using a glass with painted up the image and analyzed it along parallel and hierarchical lines, ultimately we have to combine it again into a si ng le perception. The activity of an MT Parallel processi ng Streams break up and analyze neuron in response to different aspects of a scene. For example, when we different directions of see a red bouncing ball, we perceive it as one thing , ~ , motion is shown at right. - a red bouncing ball. But in our brains some ~ ~ areas are process ing the red, others are simulta­ The cell responded strongly neously processing the spherical shape, and others to downward mot ion and are processi ng its motion. In the last 10 years it's - 000 - weakly to upward motion. been discovered that visual information is imme­ ...... In the plot in the center d iately divided in the primary visual cortex (VI) into parallel streams. For example, within VI are .. (the neuron's ~ unin g curve some repeating little patches, recently discovered 0 OJ for motion direction). the and imaginatively referred to as "blobs," which contain concentrations of nerve cells that are sensi­ ... radius length is propor­ tive to color. These cells preferentially project to a tional to the amount of particular area of V2 called the "thin stripe" area. 1 activity, and the angle to These thin stripes are involved in color processi ng, the direction of motion. and they project in turn into an area called V4,

18 E NGINEERING & SCIENCE NO. 1997 dots, however, we use high-speed, computer animation to generate these 3-D structure-from­ motion stimuli. When we project such an image onto a flat computer monicor sc reen, we lose the depth information that we would normally get from looking at the cy linder with twO eyes, but, amazingly, due to the motion signals, we ca n still perceive a revolving hollow cylinder. This com­ puter simulation demonstrates that the brain is able to use motion signals to reconstruct three­ dimensional depth. It is most interesting, how­ ever, that, since there's no depth information contained in the projected stimulus, the direction in which the cylinder appears to be rotating is ambiguous. Sometimes you may see it rotating clockwise, other times counterclockwise. And it appears to shift directions; we refer to this sponta­ neous shifting as a bistable percept. An example of another bistable percept is illustrated at right: the well-known Necker cube illusion. Some people will see the upper square as being in front, cylinders are unambiguous, and certain cells will and ochers will see the bottom square in front. If prefer certain directions of rotation. For example, you look at it for awhile, you'll see it flip sponta­ when the cyli nder is rotating counterclockwise, it neously. (Sometimes it helps if you concentrate on will generate a lot of act,ivity in a given cell. But The diagram at right one point and then on another to see the flipping.) when it's rotating in the opposite direction, the shows the activity of an Postdoc David Bradley, grad student Grace same cell is much less active. Because of the MT neuron to rotating Chang, and I trained monkeys to tell us with eye stereoscopic depth cues added to the dots, the cell movements which direction they saw the cylinders is sensitive to the thtee-dimensional structure of cylinders. The upper two rotating; we then recorded from their MT neurons. the cylinder. In the bistable state, however, in bar graphs indicate the In some trials we added in stereoscopic depth cues which the cylinder is projected on a two-dimen­ amount of activity (in in the computer display using an anaglyph tech­ sional surface and there is no depth information, action potentials per nique similar to that used in the old 3-D movies the monkey still tells us the direction he thinks of the 1950s. We found that when the monkey the cylinder is rotating. Sometimes he says it's second) when unambig­ looks at a rotating cylinder with depth cues, the rotating one way, sometimes the other. When he uous cylinders containing thinks it's rotating counterclockwise, the nerve depth cues rotated cell reliably reports this by the aCtivity it gener­ counterclockwise (left) and ates corresponding to its petception. This result indicates that we've tapped into the area of the clockwise (right). This MT cortex that is analyzing this depth from motion, cell preferred counter­ and we can actually see in the nerve-cell activity clockwise rotation. The what the monkey is perceiving. And even though the information on his retina remains the same, lower bar graphs Illustrate the cells respond differently, indicating that the activity from this same MT changes in perception-of which way the cylinder neuron, but in both cases Cylinders with disparity is turning- are occurring in this part of the brain. wth the same bistable (unambiguous) If we continue upward along the motion path­ way's hierarchical organization we co me to a tiDY cylinder that lacl(s depth area called MST (medial superior temporal area), cues. When the monkey which is about half the size of the nail on your monkey perceived the cylinder monkey percelvee pinkie finger. Humans and monkeys both,have perceives ~ rotating in the clockwise an MST; it's specialized for helping us to navigate through the world using motion information. direction, the cell was less While you're driving along a highway or walking active (left) than when he along a street, you genetate motion signals. These perceived the identical signals are called optical flow. At the poioc....:.-or ]~ n focus-toward which you're headed, there's very stimulus rotating '-....~/ little motion, but around this foc us point motion counterclockwise (right). appears to radiate out, speeding out toward the edges of the visual field like an expanding circle. Cylinders without disparity We call this spot the focus of expansion; it (bistable) corresponds to the direction in which you're heading, and it gives you useful information about

1997 ENGINEfRlNG & S(IENCE No.2 29 because that would be the point where the image is now stabilized, with everything else radiating out from it. But we know we don't do that. To find out what's going on in tbe brain during this process, we (David Btadley, Marsha Maxwell, and Krishna The upper stimulus shows Shenoy from my lab; Marcy Banks, a professor at Eyes DC Berkeley; and I) have recorded from nerve cells that when the eyes are StUl: in MST. The tuning curve of such a cell (which still, the focus of expan· Focus describes the frequency of the electrical signal sion corresponds to the = Heading coming from a cell) for an expanding stimulus is direction of heading. The shown at lower left. If the expansion point is straight ahead, this cell is firing at about half lower part of the diagram Eyes activity; if the expans ion paine is over to the right, indicates that when the Moving: the cell is very active, and if it's to the left, the same stimulus is generated Focus cell's not active at all. If we then have the monkey ~Headjtlg by the same self·motion move its eyes so that it shifts the eye's focus in the LINEA R COMBINEO ditection of the eye movement (the equivalent of direction, but the eyes are """""'" looking at the freeway sign), we find that the also tracking to the right, nerve cells shift their tuning curves to compensate generating linear motion where you're going in the world. Cells in MST are for the eye movement. The cell continues to fire tuned to these sortS of expanding stimuli generated at half activity, indicating that the monkey knows to the left, the two by motion and also to the location of the focus. it hasn't changed its heading. W hat we think is motions combine on the Now, a problem occurs when you're moving happening is that the areas in the front parr of the retina to form a pseudo· through the world in one direction but you begin brain that are sending our signals to move the eyes focus displaced in the to track something with your eyes-say a freeway are also sending signals back into the petceptual sign-that may be off to the side. Moving your areas saying: "The eye is moving; shift your direction of the eye eyes introduces a motion of your visual field in the receptive fields to compensate for it so that you movement. This pseudo· opposite direction. For example, if you hold a still perceive locations in the world as being the focus does not correspond finger in front ofyoll and follow it with your eyes same." This mechanism is called efference copy or corollary discharge, and it explains why, when we to the direction of as you move it to the right, you'll notice that everything behind it moves to tbe left. With a move our eyes around and shift the images on our heading, which is still rightward eye movement, you've introduced a eyes, the world still appears stable. We are using straight ahead. leftward motion onro the eye. If you're also information about what we're doing with our eyes moving at the same time, this retinal motion gets ro stabilize the visual world. Thus we can see that combined with the expansion signal, shifting the there is a hierarchy from Vi, which measures focus tOward the direction in which the eye is motion, to MT, which extracts the 3-D structure moving. If our brains were, in fact, using only this of surfaces in motion, to MST, which helps us new focus to guide us through the world, when we navigate through the world. looked at a sign on the freeway we'd run into it, The final processing strategy that I'll discuss is association. The bouncing red ball has now been divided up so that it's processed along three differ­ ent streams-motion, color, and shape. But since we view the world as a unitary entity, at some point we need to begin bringing this information back together again inca one picture. This bind­ ing of features back together occurs at the highest levels of the visual cortex, in the visual association areas. A few years ago, our lab described an area called LIP (lateral interparietal area), which is important for perceiving visual space and is located in the upper "where" processing Stream. LIP is also important for making eye movements by gather­ ing information from the visual cortex and . sending it to the front part of the brain to move the eyes. However, we not only move our eyes to An MST neuron tuning curve superimposed on an expansion pattern shows that the cell locate visual stimuli , but also to identify auditory stimuli. We know that our brains can perceive a responds at half its maximum response when the focus is straight ahead (left). When the sound location as easily as a visual location, but eyes are moving to the right, the focus shifts to the right, but so does the tuning curve of auditory information is collected in a very differ­ the MST neuron (right). ent way. It is assembled from auditory cues

'0 ENGINEERI N G & S(IENCE NO. '997 The schematic diagram of

the brain at right Motor illustrates the pathway of Cortex visual information that leads to visually guided

movements. Visual Primary Visual information first passes arriving ar rhe two ears, while visual information Cortex through the primary visual is imaged on the rerinas in the eyes. The brain has cortex and proceeds to combine these two very different types of sig­ nals to come up with a single, unified spatial through the posterior representation. To this point, we had tested LIP Retina parietal cortex to frontal neutons only with visual signals. We were, how­ lobe structures. The ever, interested in how rhis high-level processing area mighr combine or "associare" features of primary visual cortex is external stimuli to locate them in space. So we responsible for sensation, developed an auditory localization task. and the motor cortex for lr turned out that when Brigitte Stricanne, sending out commands to Pietro Mazzoni, and I recorded from nerve cells in the LIP area (which is a parr of rhe posterior to do one of two tasks when directed by a signal. make movements. parietal correx), we could also map tuning curves On a green signal light they were to reach in the Evidence shows that the or receptive fields for auditory stimuli. We had dark for the remembered location of a briefly early neural correlates of the monkey sit in a room with his head facing flashed target; a red signal light told them to make an eye movement (saccade) to the target plans to make movements straight ahead, keeping his head always in the same position. H e did, however, have to move instead. They had to memorize the target's loca­ appear in this pathway as his eyes to look at three different locations in the tion over a delay of one to one and a half seconds early as the posterior room. We played tones sequentially from speakers before they acted. We measured the activity of parietal cortex. in different locations in order to map the cell's specific neurons during this delay and discovered preferred location in space. When the animals that the neurons fired not only to a specific loca­ looked in the three different directions, rhe pre­ tion in the visual field but also according to ferred auditory location actually shifted in space whether the monkey was planning to look at or reach for the target. Moreover, the cells selective for eye movements were confined to area LIP, the But since we view the world as a unitaty entity, at some point we need to saccade area, and the reach-selective cells were confined to a reach area abutting LIP. This begin bringing this information back together again into one picture. anatomical segregation shows that a motor plan, guided by the visual perception, originates here in the culmination of the "where" pathway, and that by the same amount as the shift in gaze direction. the intended response, rather than the visual infor­ In other words, the selectivity of the cell to the mation, may be the determining factor in organiz­ sound moves with the eye. This finding shows ing how neural computations are made within the thar the auditory signals have been mapped onto area. This may be the place where our thoughts the same coordinate frame as the visual signals, begin to turn into actions, and where our spatial which also move with the eyes. We say that both perception is mapped not only by what our senses the auditory and visual signals are in an eye­ tell us but also by how we plan to use that centered reference frame. Auditory and visual information. D information have been brought together and asso­ ciated in LIP to form a single common perceptual representation of the world. This article was adapted from a talk given by Richard In the last couple of years we have begun to Andersen at Seminar Day in May 1996. Andersen, investigate how sensory signals lead to decisions theJames G. Boswell Professor afNeuroscience, came to and plans for action. Working in such a high­ Caltech in 1993 from MIT, where he had been a mem­ order area as the posterior parietal cortex, with so ber ofthe factllty since 1987. Before that sojourn on the many fascinating neural activities, we have won­ other coast, he had eamed his BS at U C Davis (1973) dered if intentiom might be hatched here. Since and his PhD (1979) at UC San Francisco; he was a the posterior parietal correx lies between sensory postdoc at the Johns Hopkins School of Medicine but areas and motor areas and acts as an interface returned to California as a faculty member at the Salk between them, it seemed a likely candidate for the Institute and UC San Diego. Andersen's research is l oc'~tion of the neural correlates of intention. In supported by the National Eye Institute (part of NIH), experiments published in March in Nature, Larry the Office of Naval Research, the Sloan Foundation, and Snyder, Aaron Batista, and I trained our monkeys the Human Frontiers Scientific Program.

1997 EHGIN£ERING & SCIEHCE No.2 .. Over a 3D -year career, his lab has contr ibuted to numerous branches of

molecular biology and founded a few. Here are some of the highlights.

ENGINEERING & HIENCE No . 2 1997 David Baltimore: A Short P-ortrait of a Long Career by Douglas L. Smith

If you've been reading the papers at all, you in physiology or medicine. doubtless know that David Baltimore, Coctrell Temin and Baltimore independently and simul­ Professor of Molecular Biology and Immunology taneously (the two papers were published back-to­ at MIT, found ing d irector of the Whitehead Insti­ back in the June 27, 1970, issue of Nature) discov­ cute, and former president of Rockefeller Univer­ ered an enzyme dubbed "reverse transcriptase" by sity, has agreed to become Caltech's fifth president. the unfortunately anonymous Nature correspon­ He should fit in admirably here-he has been a dent who wrote up the finding in that journal's virus man all his life, and viruses are abom as "News and Vi ews" seerion. (An enzyme is a small as biological sys tems come, so Cal tech's protei n molecule that expedites a specific chemical diminutive size should have a naeural appeal. And reaction by providing a pocket into which the like Caltech he does small science in a big way­ reactants can nestle in just the right orientation On May 13, it was over a 30-year career, hi s lab has contribuced to for the reaerion to proceed.) Temin had hypoth­ announced to the world numerous branches of molecular biology and esized the existence of reverse transcriptase­ founded a few. Here are some of the highlights. although ooc by that name-in 1964, but the idea that Cal tech's next presi­ Bal timore earned his SA in chemistry from was considered so far-fetched that most biologists dent would be biologist Swanhmore College in 1960, and he fini shed off dismissed it out of hand. Reverse transcriptase and Nobel laureate David his PhD in biology at Rockefeller University in a allows a molecule of ribonucleic acid (RNA) to Baltimore. Here he chats remarkable three years (he actually got the sheep­ copy itself into deoxyribonucleic acid (DNA), skin in '64). Postdoctoral positions foll owed at swimming against the current of information flow. with two of the people MIT and the Alben Einstein College of Med icine By the early 1960s, everyone knew that genes, who persuaded him to for a year each , leading to a three-year stint at the which are the blueprints for making every protein take the job. From left: Salk Institute in La J olla, California, where he an organism will eve r need, are encoded in DNA Kip Thorne (BS '62), co ntinued in the burgeoning field of molecular molecules in the cell's nucleus. The DN A consists biology, specializing in research on the polio vi rus. of two strands carryi ng complementary informa­ Feynman Professor of H e returned to MIT in 1968 as an associate tion, like a photograph and its negative, and the Theoretical Physics and professor, becoming a full professor in 1972. twO strands mesh together like a zipper. At the chair of the faculty search Even then, although Baltimore would spend appropriate time, the nuclear machinery unzips a most of the next three decades at That Other portion of the DNA to expose the gene's negative committee; Baltimore; and Ins titute of Technology, a Caltech connection had strand and makes positive prints in rhe form of Gordon Moore (PhD '54). been form ed. He had spent the summer after his RNA, a chemically very si milar molecule; The chair of the Board of high-school junior year at the Jackson Laboratory messenger RNAs then leave the nucleus and go Trustees. in Bar Harbor, Maine, where Howard Temin was Out into the cytoplasm (the soupy gel that makes the resident guru. Temin, who died in 1994, had up the bulk of the cell) and say co protein-making taken his PhD at Caltech in 1960 under Renato machines called ribosomes, "H ere. Make this." Dulbecco, wh o in turn had come to Caltech in "This" could be a piece of cellular machinery, 1949 to work wi th Max DelbrUck. At Caltech, an intracellular regulator that turns other genes Dulbecco developed (with Marguerite Vogt) the on and off, or even a signal to other cells-for techniques needed to grow animal viruses in instance, it might tell adjoining cells in a develop­ culture. He then headed south to the Salk [osti­ ing embryo that it's time to stan dividing and cute in 1962, where he would become one of become liver tissue. But informa tion, it seemed, Baltimore's mentors. Baltimore, Dulbecco, never traveled backward- there was no way to and Temin would share the 1975 Nobel Prize tOllch up a DN A negative from an RNA print.

199 7 EH GINEER ING & SCIENCE NO. This hunch was verified in short order, which gO t

Baltimore in the lab in the Bal timore thinking further. If a virus could carry

early days. around an enzyme to make R NA, why not one to

make DNA? The tWO molecules are very similar,

after all. Perhaps Temin was on to something.

Alice Huang, an expert on VSv. (Huang joined his lab at the Salk Institute and returned with him to MIT, where they married in 1968. She later became a professor at Harvard Medical School, and is now dean for science at New York University.) Baltimore, Huang, and a graduate student, Martha Stampfer, rapidly discovered that VSV contained a single negative strand of RNA. How, then, could the infection get started? People also knew that RNA can be a repository Simply running the negative RNA strand for genetic information in its own right. A host of through the ribosome won't suffice. Any bit of viruses had been discovered that have no DNA in protein you make will corne out all wrong, but them, but only RNA--either double-stranded like the odds are the ribosome won't get very far along DNA, or a single positive strand. In either case, the negative RNA before running into a so-called the positive RNA strand instructs a ribosome to stop codon. A stop codon shuts down the ribo­ make a protein, called RNA polymerase, that in some and ejects the completed protein and nor­ turn makes a negative RNA srrand---out in the mally appears ar [be [ail end of [he RNA strand. cytoplasm, mind you, not in the nucleus-from But in a world where black is white and white is the original positive RNA print. The RNA black, a StOp codon is JUSt as likely to appear in polymerase then makes many prints from the the middle of the RNA. In fact, it's a sure thing. new negative, and the new prints fan out to all There are no meaningless instructions in the RNA the other ribosomes in the cell, co-opting them code, so the "negative" versions of Stop codons are into making new viruses. Thus, all it takes is valid assembly instructions. Obviously, then, the one positive RNA print at one tibosome to launch "negative" versions of those assembly instructions an infection. No DNA is needed, nor is the cell 's are Stop codons, and as soon as the ribosome comes nucleus involved. In fact, many of these processes across one-and at every step it has roughly a 5 will even occur in cytoplasmic extracts from which percent chance of doing so-it turns itself off. all [he nuclei (and with them, the DNA-handling So at best, you'll get a useless snippet of protein. machinery) have been removed. Since nobody had ever found RNA polymerase But Temin had discovered that the Rous sarco­ in the cytOplasm of a normal, uninfected cell, ma virus, a single-posirive-strand RNA virus that Baltimore concluded that the VSV must be bring­ causes cancer in chickens, can't infect cells whose ing not only a negative RNA strand, but also a DNA-handling apparatus has been shut down. working RNA polymerase molecule into the cell This led him to postulate that the viral RNA in order to get [he infection starred. Once this must somehow be getting translated back into RNA polymerase had used the negative strand DNA as a prerequisi te to converting the cell into as a rem plate for assembling a posi tive copy of a cancer cell. the virus RNA out of ingredients scavenged from Meanwhile, back at MIT, Baltimore was trying the cytoplasm, the prine could run through the to apply the techniques he'd developed for study­ ribosome in the usual way. ing polio (another si ngle-positive-strand RNA This hunch was verified in shorr order, which virus) to vesicular stomatitis virus (VSV), a line got Baltimore thinking fuerher. If a virus could of research catalyzed by his postdoctoral fellow carry around an enzyme to make RNA, why not

34 ENGINEERING & S(IEN([ NO. 199 7 one to make DNA? The two molecules are very that time." The Abelson virus induces leukemia similar, after all. Perhaps Tern in was on to some­ in mice. Leukemia is a cancer of rhe blood, but thing. As Baltimore said in hi s Nobel accepcance instead of che cancerous cells congregating in a Above: The Nobel class of speech, "Luckily, I had no experience in the field rumor, they ci rculate individuall y. Normal cells and so no axe to grind- I also had tremendous divide a fixed number of times-foreordained in '75 in Stockholm. It was a respect for H oward dacing back CO my hi gh school their genes-and then quit reproduci ng and die. large group, as only the days when he had been the guru of a summer Cancer cells, with thei r altered genes, instead go literature and peace prizes school I atcended at the J ac kson Laboracory." And on dividing forever. Leukemia cells are actually were unshared that year. sure enough, Baltimore's lab found chat anocher aberrant white blood cell s, whose oversupply turns cancer-causing single-positive-strand RNA vi rus, the blood milky and gives the disease its name­ From left: Tjalling called the Rauscher virus, co ntai ns a working leukemia is Latin for "white blood." Koopmans (economics), molecule of what has come co be ca ll ed reve rse Naomi Rosenberg , then a postdoc in the Leonid Kantorovich transcriptase. Rather than creating mote RNA, Baltimore lab, developed a method for infecting the reverse transcriptase makes a negative strand of normal mouse cells with the Abelson virus and (economics), Aage Bohr DNA from the posi tive RNA, followed by then culturing them in vitro, in glass petri dishes. (physics), Eugenio Montale positive DNA that binds to the negative DNA in This provided an infinite supply of cells to (literature), Dulbecco, the nor-mal, two-stranded fas hion-aU in the host experiment on, allowing each step of the cancer­ Vladimir Prelog (chemis­ ceU's cy tOplasm. This viral DNA then sneaks into inducing process--of which the introduction of the nucleus and splices itself into the regular a cancer-causing gene, Ot oncogene, into the ceU's try), Ben Mottelson DNA, where it gets handled just like the cell 's DNA is JUSt one facet-to be studied at the (physics), Temin, John own DNA. It's now known that all cancer-causing molecular level. The process by which a healthy Cornforth (chemistry), RN A viruses get their carcinogeni c genes inca cell turns inco one of the undead is a complex Baltimore, and, from the the host cell this way. (Terni n was simultaneously molecular ballet, the choreog raphy of which is still making the same discovery with the Rous sarcoma bei ng charted worldwide. Up to thar point there Caltech class of 1939, Leo virus. Dulbecco was awarded the prize for unre­ had been no easy way to study mammalian leuke­ James Rainwater (physics). lated work that indicated that once a cell has mia in vitro-researchers had to use chi cken cells become cancerous, this new state is genetically instead. But a bi gger payoff awaited--one that stable-a finding that dovetai led nearly with would establish a new branch of immunology. Above, right: Baltimore in Baltimore's and Temin 's d iscovery.) Viruses that One of the body's chief defenses against infec­ a less formal moment, at insinuate their own genes inco the host ce ll 's genes tion is protein complexes called antibodies, which the MIT press conference are now known as retroviruses and include in their constitute about 20 percent of the free protein that followed the number HIV, the AIDS virus. circulating in our blood. Antibodies ferret Out Recalls Baltimore, "After I discovered the alien substances by means of a pocket that recog­ announcement of the reverse transcriptase, I worked for some time nizes and binds to an invadet- fot example, the Nobel Prize in October. on the biochemistry of the enzyme and tried to pocket might fit snugly over a protein that only understand how it actuall y carried Out the process exists as part of a virus's protective coating. The of reverse transcription. That was my first foray bound antibody then summons nearby white into working in cancer-inducing viruses, or cancer blood cells to engulf and devour the intruder. at all. 1 decided that if I was going to go any fur­ Each antibody's pocket is tailor-made to fit one ther, I needed a biological system to work with, specific shape, but the im mune system has to be and I was introduced by a lucky acc ident to the alert fOf an infinite number of porential threats. Abelson virus, which wasn't at all well known at Some of the menacing shapes-viral mutations

1997 ENGINEERIN G & SCIE N CE NO. that might occur in the fueure, for example--don't at around the same time, the Baltimore lab began even exist, yet the sys tem has to be ready for them working on the AIDS virus. It now appears that, when they appea r. Antibodies are secreted by regardless of what N FKB 's "real" job may prove white blood cells called B cells, each of whi ch to be, it also plays a large role in controlling HIV produces an antibody with one specific pocket. production in a class of white blood cells called Bone-marrow tissue continuously cranks out T cells. Says Baltimore, "In active T cells, it generic B-cell prec ursors which, after a few days might contribute 90 percent of HIV production." spent choosing the antibody they'll make for the In all the exci tement of unraveling immuno­ rest of their lives, become mature B cells. So, differentiation, the Abelson oncogene itself hasn't given that a B cell's nucleLL

•• ENGINfERING & SC IENCE No.1 1997 lab had previoLisly discovered. (The kinase itself is SHl, bur people rarely caB it that.) In other words, this binding event is the next step down the signaling pathway initiated by the kinase. "That is a major event in cell signaling," says Baltimore. "We spent a lot of time characterizing Collecti vely, these three domains arc involved in coordinating many :lspecrs of the nature of the interaction, bur it's been largely taken over by structural biologists." cell division , cell differentiarion, and cellular activation- just about every- The other Src-related domain, SH 3, was dis­ covered in the early '90s and was the first example thing a cell would "want" [Q do. of an entirely new class of signaling interactions. SH3 binds to stretches of protein that contain large amounts of the amino acid proline. The notion of using protein-protein interactions as a signaling mechanism had been bruited about for years, but no examples of protein domains designed expressly for that purpose had been found. Again, [he discovery ofSH 3 opened up new avenues of research, as SH3 domains have since been found far and wide. a[(ran or repel water, and their stiffness or floppi­ Collectively, these three domai ns are involved ness, among ocher things. This web of forces folds in coordinating many aspects of cell division, cell the protein up into its preferred shape. Thrusting differentiation, and cellular activation-just about a phosphate group (which has a negative charge, everything a cell would "want" to do. Says Balti­ seeks out water, and is bulky) into the web distorts more, "We're still trying to put these signaling the balance of forces and affects the protein's elements together co understand their integration, shape. And as we've seen over and over again, the as well as what pathways they're involved in. It's protein's shape confers its function-proteins are a long, complicated business." And there are vast built around pockets that are designed to do tracts of the aM gene still to be explored. something. In some cases, the phosphate gtoup With all this goi ng on, it's amazing that completes a missing part of the pocket, turn ing Baltimore gets out at all. Yet he helped develop the protein "on." In other cases, the phosphate national guidelines for genetic research back in the group obstructs or alters the pocket, turning the 1970s, and he has been a prominent figure in the protein "off." public debate over genetic engineering ever since. Other labs had discovered kinases that attach H is work with retroviruses and reverse transcript­ phosphate groups to the ami no acids serine and ase led to his being invited to help plan the threonine, bue this was the first kinase that sought research assault on AIDS in the late '80s. In the out tyrosine. The knowledge that tyrosine-rich early '90s, he was one of the architects of the feder­ proteins are amenable to the same control systems al Human Genome Project, which is now working as serine- and threonine-rich ones has opened up to discover all of the 50,000-plus genes in human new intracellular signaling pathways to explore. DNA. Most recently, in 1996, when the National But the finding has mnch broader implications. Institutes of Health created the AIDS Vaccine Many classes of enzymatic reactions are controlled Research Committee to expedite the search for by the attachment and removal of phosphate a vaccine, Baltimore was tapped to lead it- a groups-a discovery for which Edmond Fischer post he will retain as president of Caltech. and Edwin Krebs won the Nobel Prize in 1992. Baltimore sees co ntinuing to be a public figure Baltimore's lab then went on to discover two as part and parcel of charting Caltech's course into more Abl domains that are very similar to the Src the 21st century. At the press conference that (pronounced "sarc") protein, which is also involved announced his selection, he noted that the pace of in intracellular signaling in as-yet-unknown ways. scientific advance, in fields ranging from cloning The Jre gene, as its name suggests, is also related to computer science, is allowing us to do things co an oncogene, its cancerous cousin havi ng been that were impossible only a few years ago. "I look discovered in the Rous sarcoma virus we met forward to working with the Caltech faculty in earlier. (It's easy to imagine how, if the Src protein advising our society as it adjusts to these changing is part of a signal ing cascade that tells the cell rhat capabilities. I will also work with the leaders of it's time to divide, having a mutated protein stuck government, industry, and academia to help in rhe "on" position can lead to runaway cell prepare society to deal with the profound implica­ division and cancer.) tions of modern science. The role of national One Src-related domain, discovered in 1986 leadership is an important one, and Caltech has a and called Src-homology region twO, or SH2, responsibility to playa role in the debates, as they binds to the tyrosine-phosphate units created by occur, about the development of modern science the tyrosi ne-specific protein kinase the Baltimore and engineering." D

T997 ENGINEERING & SCIENCE NO. l7 Obituaries

Robert B. Leighton 1919 - 1997

Robert B. Leighton, the drawn into Caltec h's strong Even more striking were his William L. Valentine Profes­ cosmic ray g roup under Carl discoveries of a remarkable sor of Physics, Emeritus, Anderso n's leadership. He five-minute oscillation in passed away on the morning played a key rol e in 1949 in local surface velocities and of of March 9, 1997. showing that the mu-meson a "super-granulation pattern" Bob spent his entire scien­ decay products are two neu­ of horizo ntal convection cur­ tific career at Caltech, and he trinos and an electron, and he rents in large ce lls of moving established a dominating made the first measurement material. These solar oscilla­ presence in physics and of the energy spectrum of the tions have subsequently astronomy research and decay electron (at the time, been recognized as internall y teaching here. His work over low statistics experiments trapped acoustic waves, which the years spanned solid state suggested that only one neu­ opened up the whole new physics, cosmic ray phys ics, trino was involved). In 1950, field of so lar seismology, sub­ the beginnings of modern he made the fitst observation sequently pursued by Ken particle physics. solar physics, of stra nge particle decays after Libbrecht. the planets. infrared astron­ the initial discovery of twO In the early 1960s, Leigh­ omy, and millimeter- and cases in England in 1947. ron developed and fabricated submillimeter-wave astron­ Over the next seven years, he a novel , inexpensive infrared omy. In the latter four fields, elucidated many of the prop­ telescope. He and Gerry his pioneering work opened erties-for example, mass, Neugebauer used it co pro­ up entirely new scientific lifetime, decay-modes, and duce the first survey of the areas of research rhat subse­ energies--{)f several of the sky at 2.2 microns. This quently developed into vigor­ new scrange particles, in survey revealed an unexpect­ ous sc ientific communities. particular, the lambda, the xi, edly large number of rela­ In addition. he was a re­ and what were then called rhe tively cool objects. Some of nowned teacher, baving theta particles (K-mesons). these have been found to be edited The Feymllan Lectures AboU[ 1956, Leighton new stars still surrounded by in Physics into their printed became interested in the their dusty prestellar shells. form and authored a highly physics of rhe outer layers of while others are supergiant influential text, Principles of the su n. With characterisric stars in the last stage-s of their Modern Physics. For his con­ imagination and insight, he evolution, embedded in temporaries. he set a high devised Doppler-shift and expanding dusty shells of standard of teaching quality. Zeeman-effect so lar cameras. matter ejected by the scars In addition, he coauthored, They were applied with themselves. with Robbie Vogt, a set of striking success to the inves­ During the middle 1960s problems to accompany the tigation of mag netic and Leighton was the team leader Feynman lectures. velocity fields on the sun. at ]PL for the Imagi ng Sci­ In 1948, Leighton's first With the Zeeman cam era, ence Investigations on the scientific publication con­ Leighton and hi s students Mariner 4, 6, and 7 missions cerned the specific heat of mapped complicated patterns to Mars. As team leader and face-centered cubic crystals, of the sun 's magnetic fi eld an experienced experimental but he had al ready been wi th excellem resolution. physiciSt, Leighton played a

). EN GI NE ER ING & SCIENCE NO. 1997 key role in forming and was that he was always will­ guiding the development of ing to try something new and )PL's first digital telev ision different. He felt he should sys tem for use in deep space. never compete with someone, He also contributed to the but always do something fi rst efforts at image process­ unique, something that only ing and enhancement tech­ he could do. It was this niques made possible by the principle and his imagi nation digital form of the imaging that led him into the many data. and various things he did so In the 1970s, Leighton's well. He would always try interest shifted to the devel­ something new, a different opment of latge, inexpensive approach to something old, dish antenna which could be and ie paid off in a large num­ used to pursue millimeter­ ber of fundamental discover­ wave interferometry and ies made possible only by hi s submillimeter-wave as tron­ curiosity and skill. omy. Once again, hi s remark­ The hig hlight of my asso­ able experimental abil ities ciation with Bob was the Two opened a new field of science Micron Survey of the sky. at Cal tech which co ntinues to Bob was my personal friend Bob had the idea of making be vigorously pursued at the and I worked so closely with near-optical-quality mirrors Owens VaUey Radio Observa­ him as his student and then by spi nning liquid epoxy, tory (OVRO) and the Calte ch as his colleague that it is hard then a new material , and Submillimeter Observatory to limit myself to just a few leering it harden while spin­ H e would always try some- (CSO) on Mauna Kea using remembrances. ning in its natural form, a thing new, a different the "Leighton Dishes." When I first met Bob, he parabola. He llsed an air Born in Detroit, September was in the Bridge machine bearing, like one he and Vic app roach to somerhing old, 10, 1919, Dt. Leighton shop working at a lathe. The Neher had used to demon­ received his BS in 1941, his impression of that first meet­ strate frictionless mOtion to and it paid off in a large MS in 1944, and his PhD in ing- that here was a true the fres hmen students, to 1947, all from Cal tech. He "hands-on" experimentalist­ suppOrt the epoxy whi le it number of fundamental continued here as a research las ted as long as I worked was hardening. We built the fellow (1947-1949), assistant with Bob. Only later did I telescope in the Bridge discoveries m ade possible only professor (1949-1953), asso­ learn that to do a complicated mac hine shops. It was truly ciate professot (1953-1959), triple numerical integration Bob's telescope; he had built by his curiosity and skill. professor (1959-1984), the for his thesis, Bob had ma­ an "amateur" telescope at Valentine Professor of Physics chined the complicated shape home, and now he used every (1984-1985), and Valentine out of metal and weighed it. trick he had learned and more Professot, Emeritus (1985- Not only was he a great to design a 62-inch telescope, 1997). Bob served as chair experimentalist, he was a good sile for its day. Every­ of the Division of Physics, clever. thing was done on the cheap, Mathematics and Astronomy As I worked with him, I emphasizi ng Bob's cleverness. from 1970 to 1975. came to appreciate his truly We needed to "chop" to All of us who knew and awesome intellectual capabili­ rapidly sa mple alternating deeply admited Bob Leighton ties. Although an experimen­ pieces of the sky, so Bob made miss him greatly. talist, Bob could keep up the whole telescope shake with essentially any theoreti­ back and forth at 20 cycles Charles Peck cal discussion that had to do per second. Domes are Professor o/Physics with how the world worked; expensive, so Bob led a group Chair, Division of Physics, he loved physics. As a gtad­ of us-including Jerry Nel­ Mathematics and Astronomy uate student under Bob, I did son, an undergrad who would all the problems in his book. later spearhead bui lding the I don't think he was espe­ Keck LO-meter telesco p~s­ cially impressed; he expected to Me. Wilson, and we built you to do all the problems. the roll-off building to house Memorial donations may be made That was how he felt you the rele-scope. Bob had, aftet to the Los Angeles Library learned. all , built hi s own home all by Foundation at 630 West 5th Bob had about the mOst himself. The astronomy pun­ Street, Los A ngeles, California inquisitive mind I ever came dits said that at most the 90071. across. He had to know how survey would detect tens of everything worked. One rule sources; we ended up detect-

1997 ENGINEER I N G & SCIE N CE No.2 l ing thousands. The very first those days the Athenaeum coats were no longer required than generous in giving night we turned the telescope required coats and ties for for lunch. credit. When the Two Micron to the sky we detected the lunch. Although Bob nor­ As 1 said, Bob was wonder­ Su rvey was published, Bob reddest, most extteme source mally wore a coat and tie ful to work with. He pro­ insisted that 1, not he, be the that we found in the entire every day himself, he was vided inspiration for people first author, claiming that I three years of su rveying. It aware of my discomfort and at Caitech ranging from needed the exposure more was typical of Bob's good took pity. Thus one hot day undergrads to senior fac ulty. than he did. For this and luck, good luck he worked Bob took hi s coat off while Mainly he gave suppOrt and many other kindnesses, I'll hard ro have, I mighr add eating lunch at the Athenae­ enco uragemem to a large always be rhankful ro Bob that Bob's 62-inch telescope um. The horrified maitre d' number of young people. He and hope that we ca n in some now is in Washington, DC, in said , "Dr. Leighton, the rule was unstiming in helping way follow in his foots teps. the Air and Space Museum of is that coats are required." people get started. A whole the Smithsonian Institution. Bob calmly replied rhat he crop of people at Caltech got Gerry Neugebauer, PhD '60 Bob was a great friend understood the rules. Clearl y their beginning with Bob or Robert A. Millikan Professor of with a fine sense of humor the mai cre d' had done his carried out projects that Bob Physics and wonderful to know so­ duty, but Bob srood his thought of or thought were ciallyas well as in the lab. In ground and from that dayan, good to do. And he was more

did coo. The answer did not, those who couldn't fo llow an of course, always come in one abstruse line of reasoning he session--even though the was explaining might be sessions could last for many asked, "What do I have to do, hours, past meal times and say it louder?" But never, and I past other appointments that do mean never, was there any you forgot about because you animosity involved in what were so engrossed. His mem­ might seem to some to be ory was prodigious, and when harsh remarks. Nor did Ver­ he encountered a problem he ner's own ego ever intrude. Verner Schomaker 'worried it,' like a dog with a He was selfless, far more so 1914 - 1997 bone. H e might nor have all than almost anyone imagin­ the insight he wanted when able with his level of intellect the question was fits t raised and accomplishment. He was or even during the next few interested in getting things days or weeks-but he t·ight, not in who got the wou ldn't fo rget. You might credit, and was never afraid to encounter him some years admit his errors and his own Verner Schomaker, pos­ later, and he'd say, "I've been limitations, although he sessor of one of the most thinking about what you overestimated them (as he, critical and wide-ranging said, and . . " generously, did the abilities scientifi c intelleCts of our H e was at once fr iendly, of some of his co ll aborators). time, died in Pasadena, open, uncommonly generous, He is best known for his California, on March 30, and extremely bright. He contributions in electron and 1997, of pancreatic cancer. was, to those who were privi­ X-ray diffraction. He What follows is a very leged to work with him or thought that his most impor­ personal account. Many of otherwise benefit from his tant contribution had been in those who worked with or insights, simply without peer the ea rl y days of electron dif­ were closely exposed CO as a one-an-one teacher. In fraction, for development of Verner might have wri tten rhe '40s and '50s, many who techniques for the visual in­ something similar; I am worked with him fel t terpretation of the scattering confident that the general complimented when he of electrons by gas molecules. flavor would be the same. would say, "How can you be None of the structures re­ Every sc ientific question so gocldamned stupid ?" since pocted from his produCtive seemed to interest Verner, we real i zed that he expected us group had later to be revised, and anyone with a knotty to understand and that, frus­ when sector methods gave problem was welcome at hi s trated though he might be greater resolution and pre­ always-open door. And his with our slowness, he would cision. But he published in time was always yours- until not g ive up until we under­ many other fi elds as well­ he, at least, understOod in stood, or left . In his later one of his final papers (with so me depth what you were years, he learned patience and ] Urg Waser) was on the asking, and preferably you mellowed somewhat, and "Global Thermodynamics

40 ENGINEE U NG & i( IEN(E No. 1 1997 of Systems That Include Stressed Solids," and he was saddened that he could not interest any colleague in studying it intently enough to discuss it with him mea n­ ingfully. At least one of his papers became a "citation H e might not have all the insigh t he wanted when the question was firs t classic" in rhe Sc ience Cita­ cion Index. His total publica­ raised or eve n during the next few days or weeks- but he wouldn't forget . tion list, however, probably didn't reach 200 papers, You might encounter him some yea rs lacer, and he'd say, "I've been because he was a perfectionist thinking about what you said, a nd. when writing a paper, and because he was so readily distracted by the incriguing problems presented by chose who sought him out. His generous spirit, his penetrat­ ing incellect, his breadth of interests and curiosity, and Pauling quickly recognized his selflessness led almost his uncommon qualities. I always admired Verner's great brillance and his deep everyone within his orbit to After receiving a PhD in humanity. His analytical and quick mind always went to the use him as a consultant. 1938, he went up tbe aca­ nub of a problem that he faced or was presented with, and he There is little doubt that if demic ladder in chemistry at often quickly solved these problems. His mathematical there were a "Science Advisor Cal tech (taking time out for ability and his structural insights were very great and his Acknowledgment Index," be wartime tesearch from 1942 colleagues as well as industry frequently sought his advice, would have ranked at or very to 1945). In 1958 he left including the great Linus Pauling. He liberally and freely near the top. It has been academic work to join the gave of himself. His mechanical abilities were equally great, es timated that during the Union Carbide Research and premier among the many apparatus he designed, there '40s and '50s, at least one Institute (just notth of New was a fine electron diffraction machine with a rotating sector. third, and perhaps as many as York City), where be spent On a more personal note, 1 well remember a camping trip on one balf, of the papers pub­ seven years-but when it which the car broke down way out in the rules. His me­ lished by the Gates and became apparent rhat the thodical approach quickly located the ptoblem: a part in the CrelLin Laboracories (the initial promise of something distributor had broken down. Whittling a replacement out Cal tech Division of Chemis­ modeled on the Sell Labs or of a twig and carefully cutting a gasket from strong paper try) concluded with a phrase wbat was then tbe Shell readily fixed the problem. such as, "We are grateful to Development Laboratory was Verner was highly critical of ideas presented to him and Professor Verner Schomaker never going to materialize, he could be scathing and scornful. His deep-seated honesty for helpful discussions," or joined the faculty of the would not allow him to pass over any shallow or pretentious "The valuable insights pro­ Department of Chemistry at assertion ligbtly, and his criticism could be blunt. Yet he vided by our colleague Verner the University of Washington was also extremely helpful to everybody, especially to an Schomaker belped to make in Seattle. H e became underdog. Thus he cook under his wing a young fellow this work possible." And professor emeritus in 1984. recently from Switzerland who had come to study under these papets covered the After his retirement, he was Linus Pauling and was quite overwhelmed by the brillance gamut of work in the divi­ also a faculty associate at of the other students and the quality of the research at tbe sion, not just in diffraction, Caltech, dividing his time Institute. but in quantum mechanics, about equally between They say "they don't make them like that any more," but immunochemistry, NMR, Pasadena and Seattle. this is very subjective. It is mainly for us oldsters for whom spectroscopy, thermodynam­ His family has requested the world has become more lonely. I miss you, Verner, .and ics, and inorganic and organic that donations in his memory the many great and heated discussions we had. chemistry. In those years, the be made to the Verner reference "v. Schomaker, Schomaker Memorial Fund, jiirg Wa.rer, PhD '44 unpublished" was extremely California Institute of Profemy of ChemiJtry (1958-75) common-in others' papers Technology, Office of Donor especially. Relations, Mail Code 105-40, A native of Nebraska, Pasadena, California 91125. where he grew up on a farm, The fund wi ll be used to he earned a BS from that support student research. state's university in 1934 and an MS in 1935. He then Kenneth Trueblood, PhD '47 moved co Pasadena, where Professor of ChellliJtry, UCLA

199 7 ENG INEE k lNG & SCIENCE No.2 41 l control under microgravity conditions and, most recently, hydrogen/air mixing in super­ sonic combustion ramjet propulsion systems, In each of these activities Ed left his characteristic mark of objec­ tive and thorough experimen­ tal research, eschewing the experimentalist's natural diversion from the physical problem toward elegant instrumentation. Edward E. Zukoski In rhe summer of 1961, Ed participated in a fire research 1927 - 1997 study directed by Howard Emmons and sponsored by the National Research Council. The problems of unwanted forest fires and Edward E. Zukoski (MS propulsion in the center inau­ building fires appealed to '51, PhD '54), an all[hority gurated by Professor Tsien him both as a technological on the science and technology Hsue-shen the previous year. challenge and as an important of combustion, a highly It was Ed's good fortune issue of public service. Over respected member of the that experimental combustion the years Ed became a nation­ Caltech faculty fot 40 years, facilities at the J et Propulsion alleader in fire research and, and a bouyant friend co all LaboratOry were available for together with his students who knew him, died on May his use in pursuing his doc­ and his colleague Toshi Ed served as my 26, 1997, of complications toral research, which attacked Kubota, developed a compre­ attending a heart attack an urgent current problem of hensive description of con­ alterconscience; new work, several years ago. Ed pos­ combustion stability in ram­ vective fire plumes that has sessed an exuberance for jet engines and gas turbine become the technological curriculum innovations, novel life and for his work that afterbumers. In addirion to standard. A symposium on was so rich it warmed us and resolving confusion that had the fluid mechanics of fire concepts-rational and brightened our days. When persisted in the field for years, plumes, organized by his irrational-were usually first he was in good voice his Ed's work laid the founda­ former student Baki Cetegen, heatty laugh echoed through­ tions of the flame holding was held in his honot in 1996 unloaded on Ed. Oll[ all of Guggenheim. And mechanism and established at the meeting of the United with the same emotional him as an objective and States/Japan National energy, he fumed against meticulous experi_mentalist. Resources Panel on Fire stupidity and arrogance in Ed's experimental research, Research and Safety in science and in public life. together with the analysis Gaithersburg, Maryland. Ed was botnJune 29, 1927, carried out by his fellow re­ There are other facets in in Birmingham, Alabama, search scudent, Tom Adamson, Ed's life that, I think, high­ into a professionally and opened a latge field of combus­ light some of the essential socially prominent family tion issues in which the fluid attributes that make Caltech that was committed to public mechanical and chemical as­ the unique institution we service and at times espoused peers of the problem could, to know. Ed was my third doc­ liberal causes that might, a certain extent, be separated. toral student; over a period of considering the place and Ed continued his experi­ 45 years we shared a close time, see m unusual CO us and mental combustion research collegial relationship in our certainly to Birmingham at JPL for three years after research, our teaching, and society. Continuing in the completing his doctorate and the supervision of our re­ family tradition, Ed attended joined the Caltech faculty as search students. Ed served Harvard College and received assistant professor of jet pro­ as my alterconscience; new the bachelor's degree of engi­ pulsion in 1957. During his work, curriculum innova­ neering science in 1950. That long career at Caltech, Ed and tions, novel concepts­ same year he was awarded one his students made major rational and irrational-were of the new Guggenheim Fel­ innovative contributions usually first unloaded on Ed, lowships in Jet Propulsion to in other fields: magneto­ During his doctoral studies attend Caltech, studying aero­ gasdynamics, aeroacoustics, until sometime before his nautics with emphasis on jet problems of propellant marriage to Joan Breck-

42 ENGINEERING & ICIEN(E No.2 1997 Fa culty File

en ridge, he was a fixture in the Marble household. He accompanied us on camping HONORS AND AWARDS crips wirh our children, worked with us on remodel­ ling our house, and even filled in as baby-siner. He was a strong swimmer and an avid skin diver. It was not Michael Alvarez, associate recogni zes exceptional prom­ unusual on a late weekend professor of political science, ise in a young person in the afternoon for Ed to show up has been awarded a 1997 field of metallurgy. Haile at our fronc door. still damp Haynes Foundation Faculty studies solid-state ionics, from his activities, with a Fellowship for his proposal, which conduct electricity sack of abalone (those were "Who Governs Southern through ions rather than elec­ the days!) and an expression California: Will the Rise trons and are important in strongly suggesting that it of Latino Political Power fuel cells, which may one day would be great with him if Continue?" provide a clean, alternative my wife would prepare some William Deverell, associate energy source. for dinner. His suggestion Caltech's Moore Laboratory professor of history, has been Wilfred lwan (BS '57, MS was never refused. Our chil­ (above) and Avery House were elected to the board of the '58, PhD '61), professor of dren considered him family, joint ly selected to receive the California Council for the applied mechanics and frequencly more tolerant than Humanities. The Council director of the Earthquake their parencs. When, on one Crown City Award for architectural both administers a competi­ Engineering Research labora­ of our camping trips in Ari­ and/or landscape excellence from tive grants program and con­ tory, has been awarded the zona, Ed engineered the cap­ the Pasadena Beautiful ducts projects of its own, in­ 1997 Nathan M. Newmark ture of a weary tarantula, he Foundation. cluding several planned for Medal ftom the American became their hero. the California Sesquicenten­ Society of Civil Engineers In many ways Edward nial, beginning in 1998. for his contributions to the Zukoski concributed. some­ Kenneth Farley, associate dynamic analysis of buildings times energetically but often professor of geochemistry, has and other structures. quietly and unobtrusively, to been given a five-year fellow­ Jonathan Katz, assistant the quality of our lives in ship by the David and Lu ci le professor of political science. both the Guggenheim and Packard Foundation. has been selected for the 1997 the Thomas LaboratOries. He Donald Heimberger, pro­ Congressional Quarterly Press will be sorely missed. fessor of geophysics, has been Award for the best paper in selected by the American the field of legislative politics Frank E. Marble (Eng '47,PhD Geophysical Union to receive presented at the 1996 Ameri­ '48), Richard L. and Dorothy the 1997 lnge Lehmann can Political Science Associa­ M. Hayman ProJessor oj Mech­ Medal, which is awarded tion meeting. The paper, anical Engineering and Professor for outstanding contributions which he cowrote with Gary ofJet Propulsion, Emeritus to the understanding of the Cox (BS '78, PhD '83), was structure, composition, and entitled "Baker v. Carr ap.d dynamics of the Earth's Incumbency in Postwar U.S. Memorial donatiom may be sent mantle and core. House Elections." to Planned Parenthood oj Sossina Haile. assistant pro­ Wolfgang Knauss (BS '58, Pasadena, 1045 N. Lake Ave., fessor of materials science, has MS '59, PhD '63), professor Pasadena, CA 91107; or to the been chosen by the Minerals, of aeronautics and applied Wilderness Society, c/o Pamela Metals, and Materials Society mechanics, was eleered an Eaton, 7475 Daykin St., SlIite to receive the 1997 Robert Honorary Fellow by the 410, Den",,; CO 80221. Lansing Hardy Medal, which International Congress on

1997 ENGINEERING & HIENCE NO. 4. On May 8, Arnold Beckman (PhD '28) received the "Treasures of Los Angeles" award from LA mayor Richard Riordan and the Central City Association. Beckman, who was a member of the chemistry faculty until 1940 and was chairman of Caltech's Board of Trustees from 1964 to 1974. has given approximately $270 million for the direct support of research, much of it in universities in Southern California. Here he is congratulated at the award ceremony by Harry Gray, the Beckman Professor of Chemistry Fracture for "contributions Institute in Florence, Italy. in dynamic fracture." David Rutledge, professor and director of the Beckman Gordon Moore (PhD '5 4), of electrical engineering, has Institute. chair of Caltech's Board of received the Microwave Trustees and cofounder of Theory and Techniques So­ the Intel Corporation, has ciety's 1997 Distinguished received the Chairman's Educator Award. Award from San Jose's Tech Edward Stolper, the Leon­ Museum of Innovation. The hard Professor of Geology and EVERHART CHAIR ESTABLISHED Chairman's Award recognizes Chair of the Division of extraordinary dedication to Geological and Planetary the museum's educational Sciences, has been named a mission and to the better­ Geochemistry Fellow by the ment of Silicon Valley European Association for In a twist on the familiar story of the retiring executive through philanthropy and Geochemistry for his out­ who departs with the gift of a commemorative chair, Caltech volunteer involvement. Pre­ standing contributions to President Tom Everhart has been given a chair in the full vious recipients are William geochemistry. expectation that he will leave it behind. It is the Thomas E. Hewlett and David Packard. Peer Vogel, senior research and Doris Everhart Professorship, endowed by the Institute Ster! Phinney (BS '80), associate in physics and trustees in recognition of the Everharts' decade of service to professor of theotetical astro­ lecturer in physics, has been Caltech. Trustees Chair Gordon Moore (PhD '5 4) announced physics, has been elected a elected a Fellow of the the creation of the Everhart Chair at a trustees' dinner held in Fellow of the American American Physical Society the Everharts' honor in May. The initial recipient will be in the Physical Society for his for his innovative theoretical biological sciences. contributions to the under­ work in double-beta decay Moore also announced that the trustees have established standing of black hole dy­ and neutrino interactions, the Doris Everhart Award, which will be presented annually namics, active galactic nuclei including his definitive cal­ to an undergraduate who has "actively supported and willingly and quasars, binary and milli­ culations of reactor neutrino worked for organizations that enrich not only student life but second pulsars, and globular spectra. also the campus and/or community as a whole, and who has, in cluster dynamics; and for his Ahmed Zewail, the Pauling addition, exhibited care and concern for the welfare of students method of measuring the Professor of Chemical Physics on a personal level. " intergalactic magnetic field. and professor of physics, has The Everharts' name will also be associated with under­ David Politzer, professor been named the 1997 recipi­ graduate education through the Thomas E. and Doris Everhart of theoretical physics, has ent of the Robert A. Welch Endowed Scholarship Fund, established by the President's Circle been awarded a Guggenheim Award in Chemistry, pre­ of the Caltech Associates. Thus far, more than $400,000 has Fellowship for 1997, one sented by the Welch Founda­ been pledged in endowments, ensuring the creation of a Thomas of only 164.appointed this tion for "outstanding contri­ E. and Doris Everhart Scholarship, which will be awarded to an I year in the U. S. and Canada. butions to chemistry for the outstanding student. Associates President Milton Mohr made Robert Rosenstone, pro­ betterment of humankind." [J the announcement as a surprise to the Everharrs at the fessor of hisrory, has been President's Circle Garden Party in June. selected for the 1997-98 And the Graduate Student Council has named its lecture Florence Fulbright Chair series the T. E. Everhart Distinguished Graduate Student at the European University Lecture Series. n

44 E~GIN[[RING & SCIENCE ~O. ' 997 Tom and Doris Everhart shook hundreds of hands as they said goodbye to the campus during a gala luncheon on the Court of Man June 5. The entire Caltech community­ facu lty, students, and staff-turned out to celebrate the past 10 years and to wish the Everharts well in their new home in Santa Barbara.