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

    trange rocks and silken ers ters 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, university geologists agreed tte tributed to some ancient, unspecifiedvolcanic action. 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.

    tone t 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—indeed, tively 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 can see danger from a long ually tourned out at one end of Main Street and cornado came to ly scampered . Four of t move quite fast enougcalled Crater Days,  un doesn’t really o do er. Nobody’s figured out a o capitalize on an impact site t isn’t visible.

    “Very occasionally  people coming in and asking er and ell t to see,” says Anna Scoed.”  people,including most Ios it barelyrates a footnote. But for one brief period in t geologicallyexciting place on Earth.

    tory begins in t young geologist named EugeneS to Meteor Crater in Arizona. today Meteor Crater is t famousimpact site on Eartourist attraction. 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-ton meteor, ed  ation t une digging it out.

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

    By tandards of today, crater researcrifle unsopicated, tosay t. tigator, G. K. Gilbert of Columbia University, modeledts of impacts by flinging marbles into pans of oatmeal. (For reasons I cannot supply,Gilbert conducted ts not in a laboratory at Columbia but in a el room.)Some concluded t ters s—in itself quite a radical notion for time—but t t. Mostscientists refused to go even t far. to ters volcanoes and noters t remained evident on Eart 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 explosion rings at ts nuclear test sitein Nevada.  t MeteorCrater to suggest volcanic activity, but t tributions of otuff—anomalous fine silicas and magnetites principally—t suggested an impact from space.

    Intrigued, o study t in ime.

    orking 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 in tietury essentially abandonedtem,” tention urned to 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 place and teroid actually a million miles from its nearest neigely eroids tumbling t t to be probably not lessto be planets t never quite made it, oo ttling gravitational pull of Jupiter, hem from coalescing.

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

    Finding asteroids became a popular activity in turyabout a t no one ematically recordingt en become impossible to knopopped into vie ed earlier and t track of. Bytime, too, astrop feronomers ed to devoteto anytoids. Only a feronomers, notablyGerard Kuiper, tcronomer for s is named,took any interest in tem at all. to  toryin texas, folloer by  t Center in Cincinnati andtc in Arizona, a long list of lost asteroids led doil by tietury only one knoeroid ed for—anobject called 719 Albert. Last seen in October 1911, it racked doerbeing missing for eighty-nine years.

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

    In a sense it 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 space and  do is beyond guessing. Any asteroid outt  is very likely to her.

    t as a kind of freeepping off t least 90 percent of trians are quite unknoo us. e don’t kno of en t atsome point, at uncertain intervals, trundle across tsixty-six teven Ostro of t Propulsion Laboratory  it,“Suppose t tton you could pus up all teroids larger t ten meters, 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 can’t see it.

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

    According to timoting in times a iced.

    An object a  be picked up by any Eartelescope 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 McDonald’srestaurant. (It is actually some mucrying to get people galvanized about tential dangers oftem, anot——lyunfolding in Italy  from t Doy Laboratory atColumbia University. In ter Alvarez taccione Gorge, near to 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 account for sucic moment in Eartory.

    At time tional  tinction  ury earlier—namely t t overmillions of years. But ted t in Umbria, if1It is Kt rat because C ed for Cambrian. Depending on a or German Kreide. Botly mean “c Cretaceous means.

    noely in tests existed for determining  migaken to accumulate.

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

    Every year tes some ty tric tons of “cosmicsp 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, ecion of clays using a process called neutron activation analysis. trons in a small nuclear reactor and carefully counting t ted; it remely finicky tery, but Alvarez reasoned t 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 confirm irely self-evident to begin  ts ted. Certainly no one expected o yield any dramaticbreakthroughs.

    “ell, terview in 2002.

    “And it seemed an interesting co try. Unfortunately, I  of ot o it.” ed es from t 1:45 p.m.,  a sample in tector. It ran for 224minutes and ting interesting results, 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 probablycataclysmic, ing spike.

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

    t t be subjected to devastating impacts from time to time quite as ne is noimes presented. As far back as 1942, a NorternUniversity astrop named Ralped sucy in 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  unkno Oregon State University, M. . de Laubenfels, ing in tology, ually anticipated ting t t adeat from space, and in 1970 t of tological Society, De ty t an extraterrestrial impact may  knoinction.

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

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

    But it did. It icularly in tological community,as an outrageous heresy.

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

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

    Nor did it  Luis Alvarez emptuous of paleontologists and tributions to scientific kno very good scientists. tamp collectors,” e in times in an article t stings yet.

    Opponents of ternative explanations for ts—for instance, t ted by prolonged volcanic eruptions inIndia called traps—and above all insisted t t tly from t t vigorous opponents ed t ted by volcanic action even  ual evidence of it. As late as 1988 more tologists contacted in a survey continued to believe t tinction of ted to an asteroid or cometary impact.

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

    Geology is a profession t varies from place to place. In Ioate t is flat andstratigrapful, it tends to be comparatively serene. t deposits of oil or precious metals, not a  of a pyroclastic flow.

    If you are a geologist employed by tate of Io of toevaluate Manure Management Plans, e’s “animal confinement operators”—o t of us—are required to file periodically. teen million  of manure to manage. I’m not mocking t all—it’s vital and enlig keeps Ioer clean—but  ’s not exactly 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 specimen stones. (Geologists are never at a lossfor paper to find anytra celepo move stacks of documents 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, producing a small painedsmile.

    “It zke  on. “tually quite a lot of badscience 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 inction. 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 conference in Souta and found people coming up to tic looksand saying: “e  your crater.” It  t Izett and tists  announced refined figures revealing t Manson couldn’t after allinction crater.

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

    “?”

    ty good insigo tractivescience can get ain level.”

    ty of Arizona, met a reporter from ton Co kno a large, unexplained ring formation, 120 miles án Peninsula at Cy of Progreso, 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 satisfaction 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?”

    Conveniently a natural test of t Ser. For t time,o ness a cosmic collision—and ness it very o telescope. Most astronomers, according 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 million megatons—seventy-five times moretence. Nucleus G  tain, but it created  ics of theory.

    Luis Alvarez never kneer or of t, as , ralian outback, o searc sites. On a dirt track in tanami Desert—normally one oftiest places on Eart rise just as anotantly,  of  totor spacecraft. t tered around MeteorCrater.

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

    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 actuallycomparatively pristine.”

    I asked tooday.

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

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

    An asteroid or comet traveling at cosmic 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 crinkle and vanish like cellophane in aflame.

    One second 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 approac since it all building in Omao look in t direction urmoil folloantaneous oblivion.

    ites, over an area stretco Detroit and encompassing 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 cating earto rumble and spesunamis ingly for distant s, and burning rock and oting doing muc ablaze. It imatedt at least a billion and a  day. turbances to t communications systems everyurn. It er. As one commentator  it, fleeing ing a slooll tle affected by any plausible relocation effort, sinceEarty 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 impact and concluded t it affected Earte for about ten thousand years.

    tually used as evidence to support tion t tinction of dinosaurs  and empic—and so it erms. e can only guess y .

    And in all likeli  of a clear sky.

    But let’s assume  coming.   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 housecleaning exercise.

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

    Sing Jupiter in a fairly conspicuous manner since 1929, but ittook over ury before anyone noticed.

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

    For most of time of t’s approac in a kind of cone of uncertainty.

    It ainly be t interesting 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 minor event. Do you knoions ed ?”

    “No idea,” I replied.

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

    Of course, itzke and Anderson added ily and more or less in unison, terrible devastation across muc described, and completeanniion for  life is  none permanentlyperished.

    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.