PEOPLE KNE FOR a long time t t toer supply reported bringing up alot of strangely deformed rock—“crystalline clast breccia    matrix” and “overtura flap,” as it er described in an official report. ter oo. It    as soft as rainer. Naturally    soft er had never been found in Iowabefore.

        trange rocks and silkeers of curiosity, forty-oneyears eam from ty of Io around to making a trip to ty, to t part of tate. In 1953, after sinking a series of experimental bores, uy geologists agreed tte tributed to some a, unspecifiedvolic a. t it    as.

        trauma to Manson’s geology    from    from at least 100million miles beyond. Sometime in t past,    a mile and a en billion tons and traveling atpermospo t ant a y miles across.

        to elseerated andreplaced by t rocks t so puzzled ter driller in 1912.

        t    t edStates. Of any type. Ever. ter it left be if you stood on oneedge you    be able to see t    and trifling. Unfortunately for lovers of spectacle, 2.5 million years ofpassing ice ss filled ter rigo top ill, tsmoot today t Manson, and for miles around, is as flat as a tabletop.

        er.

        At ted to sion of neiclesand a box of core samples from a 1991–92 drilling program—iively bustle toproduce t you o ask to see t is on display, andnoorical marker.

        to most people in Manson t to ornado t rolled upMain Street in 1979, tearing apart trict. One of tages of all tsurrounding flatness is t you    see danger from a long ually tourned out at one end of Main Street and ado came to ly scampered . Four of t move quite fast enougcalled Crater Days,    u really o do er. Nobody’s figured out a o capitalize on an impact site t isn’t visible.

        “Very occasionally    people ing in and asking er a to see,” says Anna Scoed.”    people,including most Ios it barelyrates a footnote. But for one brief period in t geologicallyexg pla Earth.

        tory begins in t young geologist named Eugeo Meteor Crater in Arizona. today Meteor Crater is t famousimpact site oourist attra. In t didn’t receivemany visitors and ill often referred to as Barringer Crater, after a aked a claim on it in 1903. Barringer believedt ter en-million-toeor, ed    ation t une digging it out.

        Una teor and everyt une, and t ty-six years, cutting tu yielded nothing.

        By tandards of today, crater researcrifle unsopicated, tosay t. tigat. K. Gilbert of bia Uy, modeledts of impacts by flinging marbles into pans of oatmeal. (For reasons I ot supply,Gilbert ducted ts not in a laboratory at bia but in a el room.)Some cluded t ters s—in itself quite a radiotion for time—but t t. Moststists refused to go even t far. to ters voloes and    remained evident o tributed to otreated as fluky rarities.

        By time S Meteor Crater eam explosion. S undergroundsteam explosions—: t exist—but    blast zones. Oneof    jobs out of college o study explosis at ts est sitein Nevada.    t MeteorCrater to suggest volic activity, but t tributions of otuff—anomalous fine silicas and mages principally—t suggested an impact from space.

        Intrigued, o study t in ime.

        first er e David Levy, Sematic survey of tem. t one ory in California looking for objects,asteroids primarily, ories carried t.

        “At time arted, only sligire course of astronomical observation,” Ser in a television intervieronomers iury essentially abaem,” tention uro tars, the galaxies.”

        S t tdeal more—than anyone had ever imagined.

        Asteroids, as most people knos orbiting in loose formation in a beltbeter. In illustrations ting in a jumble, butin fact tem is quite a roomy plad teroid actually a million miles from its    neigely eroids tumbling t t to be probably not lessto be pla never quite made it, oo ttling gravitational pull of Jupiter, hem from coalesg.

        eroids    detected in t day of tury by a Sicilian named Giuseppi Piazzi—t to be plas, andt t took some inspired dedus by tronomer illiam o    t t sized but muceroids—Latin for “starlike”—u like stars at all. Sometimes noely called plaoids.

        Finding asteroids became a popular activity in turyabout a t no oically rect en bee impossible to knopopped into vie ed earlier and t track of. Bytime, too, astrop feronomers ed to devoteto anytoids. Only a feronomers, notablyGerard Kuiper, ter for s is ook any i i all. to    toryin texas, folloer by    t ter in ati andt Arizona, a long list of lost asteroids led doil by tietury only one knoeroid ed for—a called 719 Albert. Last seen in October 1911, it racked doerbeing missing fhty-nine years.

        So from t of vieeroid researcietury ially just along exercise in bookkeeping. It is really only in t fe astronomers o t and keep an eye on t of teroid unity. As of July 2001,ty-six teroids ified— to a billion to identify, t obviously has barely begun.

        In a se ters. Identifying an asteroid doesn’t make it safe. Even if everyasteroid in tem , no one could say urbationsmigling to forecast rock disturbances on our o t in spad    do is beyond guessing. Any asteroid outt    is very likely to her.

        t as a kind of freeepping off t least 90 pert of trians are quite unknoo us. e don’t kno of en t atsome point, at uain intervals, trundle across tsixty-six teven Ostro of t Propulsion Laboratory    it,“Suppose t tton you could pus up all teroids larger t teers, ts in t, you    a couple of tant tars, but millionsupon millions upon millions of nearer, randomly moving objects—“all of    courses t different rates. It    ist ’t see it.

        Altoget is t—t is really only a guess, based orapolating fromcratering rates on t some teroids big enougo imperilcivilized existence regularly cross our orbit. But even a small asteroid—troy a city. tive tiddlers is isalmost certainly in to track.

        t one    spotted until 1991, and t er it    iced as it sailed past us at a distance of 106,000 miles—in ic termst of a bullet passing t toucer, anot larger asteroid missed us by just 90,000 miles—t pass yetrecorded. It, too,    seen until it    warning.

        Acc to timoting in times a iced.

        An object a    be picked up by aelescope untilit    a fe is only if a telescope o be trained on it,. ting analogy t is al tively searceroids is feaff of a typical Mald’srestaurant. (It is actually some mug to get people galvanized about tential dangers oftem, anot——lyunfolding in Italy    from t Doy Laboratory atbia Uy. In ter Alvarez tae Ge, o divided t layers of limestone—onefrom taceous period, tertiary. t knoo geology ast boundary,1and it marks time, sixty-five million years ago, wly vanishe fossil record.

        Alvarez     a ter of an inc could at for sucient iory.

        At time tional    tin    ury earlier— t overmillions of years. But ted t in Umbria, if1It is Kt rat because C ed for Cambrian. Depending on a erman Kreide. Botly mean “c Cretaeans.

        noely is existed for determining    migaken to accumulate.

        In t certainly    t, but luckily ion to someoside    nuclear p;tac to rocks, but trigued    occurred to    t lie in dust from space.

        Every year tes some ty tris of “icsp in plainer language— if you s it intoone pile, but is infinitesimal ingare exotic elements not normally muc iridium, in space t (because, it ist, most of to t was young).

        Alvarez kne a colleague of    tory in California,Frank Asaro, e of clays using a process called ron activation analysis. trons in a small nuclear reactor and carefully ting t ted; it remely finicky tery, but Alvarez reaso if tof one of tic elements in    s annual rateof deposition, t aken to form. On an Octoberafternoon in 1977, Luis and alter Alvarez dropped in on Asaro and asked ests for them.

        It e a presumptuous request. to devote montomaking t painstaking measurements of geological samples merely to firm irely self-evident to begin    ts ted. Certainly no one expected o yield any dramaticbreakthroughs.

        “ell, terview in 2002.

        “And it seemed an iing co try. Unfortunately, I    of ot o it.” ed es from t 1:45 p.m.,    a sample ior. It ran for 224minutes and ting iis, so opped it and had alook.”

        ts ed, in fact, t tists at first t tobe    of iridium in timesnormal levels—far beyond anyt ed. Over to ty    a stretcarted you couldn’t stop,” Asaro explained) analyzing samples, als.

        tests on otarctica—s t ly elevated every, and probablycataclysmig spike.

        After muc, t t plausible explanation—plausible to t any rate— truck by an asteroid or et.

        t t be subjected to devastating impacts from time to time quite as ne is noimes presented. As far back as 1942, a NorternUy astrop named Ralped su anarticle in Popular Astronomy magazine. (icle to run it.) And at least tists, tronomerErnst ?pik and t and Nobel laureate    for tion at various times. Even among paleontologists it    unknon State Uy, M. . de Laubenfels, ing in tology, ually anticipated ting t t adeat from space, and in 1970 t of tological Society, De ty t araterrestrial impact may    knoin.

        As if to underline just ime, in 1979 audio actually produced a movie called Meteor (“It’s five miles ’sing at 30,000 m.p. alieood, Karl Malden, and a very large rock.

        So    a meeting of tion for t of Sce, t tin taken place over millions of years as part of some slosuddenly in a single explosive event, it s have e as a shock.

        But it did. It icularly in tological unity,as an eous heresy.

        “ell, you o remember,” Asaro recalls, “t eurs in ter specializing in paleomagism, Luis ologists t ’s not terribly surprising t t embrace itimmediately.” As Luis Alvarez joked: “e    alise.”

        But tally ab in tt terrestrial processes ural orysiime of Lyell. By tastrop of fas iterally unt geologists tating impact    tific religion.”

        Nor did it    Luis Alvarez emptuous of paleontologists and tributions to stifiood stists. tamp collectors,” e in times in an article t stings yet.

        Oppos of ternative explanations for ts—for insta ted by prolonged volic eruptions inIndia called traps—and above all insisted t t tly from t t vigorous oppos ed t ted by volic a even    ual evidence of it. As late as 1988 more tologists tacted in a survey tio believe t tin of ted to an asteroid or etary impact.

        t    obviously support t    site. Enter Eugene Sion—er-in-laaug ty of Ioo uro Iowa.

        Geology is a profession t varies from place to place. In Ioate t is flat andstratigrapful, it tends to be paratively sere deposits of oil or preetals, not a    of a pyroclastic flow.

        If you are a geologist employed by tate of Io of toevaluate Manure Ma Plans, e’s “animal fi operators”—o t of us—are required to file periodically. teen million    of mao manage. I’m not mog t all—it’s vital and enlig keeps Ioer —but    ’s ly dodginglava bombs on Mount Pinatubo or scrabbling over crevasses on t insearc life-bearing quartzes. So ter of excitement ts tment of Natural Resources ion focused on Manson and its crater.

        trourn-of-tury pile of red brick t y of Ioment and——ts of tment of Natural Resources. No one noee geologists y, but you get t t very accessible.    to be taken outonto a roof ledge and hrough a window.

        Ray Anderson and Brian itzke spend ts, and y spe stones. (Geologists are    a lossfor paper to find anytra celepo move stacks of dots around.

        “Suddenly    ter of told me, gleaming at t,    ime.”

        I asked t Gene So have been universally revered.

        “ a great guy,” itzke replied    ation. “If it    been for ten off t, it took to get it up and running. Drilling’s an expensive business—about ty-five dollars a footback to go do.”

        “Sometimes more t,” Anderson added.

        “Sometimes more t,” itzke agreed. “And at several locations. So you’re talking alot of money. Certainly more t would allow.”

        So    a    collaboration    he U.S.

        Geological Survey.

        “At least    it ion,” said Anderson, produg a small painedsmile.

        “It zke    on. “tually quite a lot of badsce going on t ts t didn’t aland up to scrutiny.” One of ts came at ting of tt and C. L. Pillmore of t ter    age to in. tion attracted a good deal of press attention but unately premature. A more careful examination of ta revealed t Manson    only too small, but also nine million years too early.

        t Anderson or itzke learned of tback to t a feren Souta and found people ing up to tic looksand saying: “e    your crater.” It    t Izett and tists    announced refined figures revealing t Manson couldn’t after allin crater.

        “It ty stunning,” recalls Anderson. “I mean, ant and t    anymore. But even iont t ing    boto sheirnew findings.”

        “?”

        ty good insigo tractivesce    get ain level.”

        ty of Arizona, met a reporter from ton o a large, unexplained ring formation, 120 miles án Peninsula at Cy reso, about 600 miles due soution ally, t Gene S visited Meteor Crater in Arizona—but ts    it he day.

        raveled to te and decided fairly sly t ter. By early1991 it abliso nearly everyone’s satisfa t Csite.

        Still, many people didn’t quite grasp    could do. As Steprong initial doubts about t . . . [] only six miles across er of eighousand miles?”

        vely a natural test of t Ser. For t time,o ness a ic collision—and ness it very o telescope. Most astronomers, acc to Curtis Peebles, expected little,particularly as t    a co sp a string of ty-one fragments. “Mysense,” e one, “is t Jupiter s up    so much as a burp.”

        One , Nature ran an article, “tingt t itute noteor shower.

        ts began on July 16, 1994,    on for a ion of Gene Sed. One fragment, knoruck    six milliooy-five times moretenucleus G    tain, but it created    ics of theory.

        Luis Alvarez never kneer or of t, as , ralian outback, o searc sites. On a dirt tra tanami Desert—normally oiest places o rise just as anotantly,    of    totor spacecraft. t tered aroueorCrater.

        Anderson and itzke no longer er t killed t ill    and most perfectly preserved impact crater iates,”

        Anderson said. (A little verbal dexterity is required to keep Manson’s superlative status. Oters are larger—notably, C site in1994—but to ters of limestone and mostly offs difficult to study,” Anderson on, “’s because it is buried t it is actuallyparatively pristine.”

        I asked tooday.

        “O    be visible to tilit     il it    tmosp onesed before it    talking about sometens of timesfaster test bullet. Unless it elescope, and t’sby no means a certainty, it ake us pletely by surprise.”

        or s depends on a lot of variables—angle of entry, velocity andtrajectory, ing object, among mucer t. But ists    do—and Anderson and itzke    site and calculate t of energy released. From t tplausible sarios of    must happened now.

        An asteroid or et traveling at ic velocities er tmospsuc t couldn’t get out of tly, and temperature belo o some 60,000 Kelvin, or ten times temperature of tant of its arrival in our atmospeor’s patories, cars—would kle and vanish like cellophane in aflame.

        One sed after entering tmospeorite o t before been going about their business.

        teorite itself antly, but t    a ters of rock, earted gases. Every living t been killed by t of entry . Radiating outalmost t ial s.

        For tside te devastation, t inkling of catastrop—test ever seen by ant to aminute or ter by an apocalyptic sigo tire field of vieraveling atts approace it all building in Omao look in t dire urmoil folloantaneous oblivion.

        ites, over aretco Detroit and enpassing y, ties—t, ins—nearly every standing ttened or on fire, and nearly every living to a t and slicedor clobbered by a blizzard of flying projectiles. Beyond a tation fromt would gradually diminish.

        But t’s just tial s teddamage    it    certainly set off a g earto rumble and spesunamis ingly for distant s, and burning rod oting doing muc ablaze. It imatedt at least a billion and a    day. turbao t unications systems everyurn. It er. As one entator    it, fleeing ing a slooll tle affected by any plausible relocation effort, siy to support life would be universally diminished.”

        t of soot and floating as and follo out tainly for monting groitute of tecopes from sediments left from ter Kt impad cluded t it affected Earte for about ten thousand years.

        tually used as evideo support tion t tin of dinosaurs    and empid so it erms. e    only guess y .

        And in all likeli    of a clear sky.

        But let’s assume    ing.     to smit, as Joes, our missiles are not designed for space    to escape Earty and, even if toguide tens of millions of miles of space. Still less could    po t could,Saturn 5, ired years ago and urn launcroyed as part of aNASA houseing exercise.

        Even if    a eroid and blasted it to pieces,t urn it into a string of rocks t o us oer t Ser—but    noensely radioactive. tom Geeroid er at ty of Arizona, t even a year’s    totake appropriate a. ter likeli    see any object—even a et—until it    six montoo late.

        Sing Jupiter in a fairly spianner since 1929, but ittook over ury before aiced.

        Iingly, because t to pute and must incorporate suc margin of error, even if    il nearly t couple of weeks anyway—wain.

        For most of time of t’s approa a kind of e of uainty.

        It ainly be t iing feory of ty if it passed safely.

        “So en does somet zke before leaving.

        “O once every million years on average,” said itzke.

        “And remember,” added Anderson, “tively mi. Do you knoions ed ?”

        “No idea,” I replied.

        “None,” range air of satisfa. “Not one.”

        Of course, itzke and Anderson added ily and more or less in unison, terrible devastation auc described, and pleteanniion for    life is    none permalyperished.

        t appears, is t it takes an a to extinguis ted on. orse still, it isn’t actually necessary tolook to space for petrifying danger. As    to see, Earty of dangerof its own.
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