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Comet/Asteroid Impacts and Human Society: An Interdisciplinary Approach
Abstract
In 1908 an atmospheric explosion in northern Siberia released energy equivalent to 15 Mton of TNT. Can a comparable or larger NEO affect us again? When the next NEO strikes Earth will it be large enough to destroy a city? Will the climate change significantly? Can archaeology and anthropology provide insights into the expected cultural responses with NEO interactions? Does society have a true grasp of the actual risks involved? Is the Great Depression a good model for the economic collapse that could follow a NEO catastrophe? This volume provides a necessary link between various disciplines and comet/asteroid impacts.
Chapters (33)
The Earth is the most geologically active of the terrestrial planets and it has retained the poorest sample of the record of hypervelocity impact by interplanetary bodies throughout geologic time. Although the surviving sample of impact structures is small, the terrestrial impact record has played a major role in understanding and constraining cratering processes, as well as providing important ground-truth information on the three dimensional lithological and structural character of impact structures (Grieve and Therriault 2004). Recently, there has been a growing awareness in the earth-science community that impact is also potentially important as a stochastic driving force for changes to the terrestrial environment. This has stemmed largely from: the discovery of chemical and physical evidence for the involvement of impact at the Cretaceous-Tertiary (K/T) boundary and the associated mass extinction event (e.g. Alvarez et al. 1980; Smit and Hertogen 1980; Bohor et al. 1984), and their relation to the Chicxulub impact structure in the Yucatan Peninsula, Mexico (Hildebrand et al. 1991), the recognition of the resource potential of impact structures, some of which are related to world-class ore deposits, both spatially and genetically (Grieve and Masaitis 1994; Grieve 2005), and the recognition of the potentially disastrous consequences of impacts for human civilization (Gehrels 1994).
Humans and cosmic impacts have had a long and intimate relationship. People live in ancient impact craters, such as at Ries and Steinheim in Germany, and use impact breccias for building material. People historically witnessed and venerated fallen meteorites, in some cases the meteorites becoming among the most sacred of objects - such as that kept in the Kaaba at Mecca. People made tools from meteoritic iron, including certain examples from the objects named the tent, woman, and dog by the Greenland Eskimos. And in one of the more peculiar ironies linking humans and cosmic impacts, people carved a portion of an ancient Ohio impact crater into the shape of a Great Serpent. This act not only created one of the more spectacular archaeological sites in North America, but also depicted a symbol used by a number of cultures to represent comets, the very source of some impact craters on the Earth.
The celestial environment has always played a significant role in the shaping of human culture. Written records spanning thousands of years are replete with examples of the importance of the celestial constants (e.g. the Sun, moon, stars, planets) in the basic ideologies and the everyday lives of peoples around the world. Of equal or greater importance are transient celestial phenomena (e.g. eclipses, meteor storms, asteroids, comets). Because of the infrequency, unpredictability, and often fantastic manifestations that are presented by these transient events, they have been viewed as having much greater import than the much more predictable celestial constants.
Master (2001) discovered a ca. 3.4 km diameter circular structure, in the marshes of southern Iraq, on published satellite imagery (Fig. 4.1, after North 1993a), and interpreted it to be a possible meteorite impact crater, based on its morphology (its roughly polygonal outline, an apparent raised rim and a surrounding annulus), which differed greatly from the highly irregular outlines of surrounding lakes. The structure, which is situated in the Al ’Amarah Marshes, near the confluence of the Tigris and the Euphrates Rivers (at 47° 4′ 44.4″ E, 31° 8′ 58.2″ N), was identified by Master (2002) as the Umm al Binni lake, based on a detailed map of the marshes published by Wilfred Thesiger (1964). Following the Gulf War of 1991, Saddam Hussein’s regime embarked on a massive program to drain the Al ’Amarah marshes, by building a huge canal named the “Glory River” parallel to the Tigris River (Fig. 4.3) (North 1993a, b; Wood 1993; Pearce 1993, 2001; Partow 2001a; Naff and Hanna 2002). After the almost complete draining of the marshes since 1993 (Munro and Touron 1997; Partow 2001a, b; Nicholson and Clark 2002) the Umm al Binni Lake has disappeared and in recent Landsat TM and ASTER satellite imagery, it appears as a light colored area, due to surface salt encrustations (Fig. 4.4). Following the Iraq War of 2003, there are moves afoot to re-flood the marshes in an attempt to restore its devastated ecology (Brookings Institution 2003;
Jacobsen 2003; Lubick 2003; Martin 2003; Sultan et al. 2003; Richardson et al. 2005; Lawler 2005).
The dates of a series of narrowest ring events (dates where numbers of long-lived oaks showed catastrophically narrow growth rings at the same time) have been identified in a long Irish oak tree-ring chronology (Baillie and Munro 1988). The dates were christened ‘marker dates’ because they were immediately noted to fall in clusters of information relating to traumatic happenings in widely separated areas around the world. For example, one of the Irish oak dates was 207 BC. In China events in 208 BC, and the years following, included a dim Sun, crop failures, famine and high death rates; and a new dynasty, the Han, is believed to have started in 206 (Pang et al. 1987). Meanwhile, in Europe, problems in Rome called for consultation of the Sibylline Books resulting in the return of the Goddess Cybele from Asia Minor; Cybele was manifest as a ‘small black meteorite.’ This latter occurrence made sense of a series of references by Livy to ‘stones falling from the sky’ and strange lights in the sky, ‘prodigies of Jupiter’, et cetera (Forsyth 1990). Clearly, dates around 207 BC might be expected to show up in other records.
The threat posed to our planet and our civilization by future comet and asteroid impacts (CAIs) is now widely recognized and is becoming increasingly well constrained. Recent studies have provided tighter estimates of the numbers of potentially-threatening objects, particularly within the near-Earth space (Near Earth Object Science Definition Team 2003), better approximations of likely frequencies of collision with objects of various diameters (e.g. Chapman 2004), and a more realistic appreciation of the effects of CAIs on society and the environment (e.g. Toon et al. 1997; Morrison et al. 2004). In this regard, the hazard and risk associated with CAIs are now far better comprehended than those linked with other geological and geophysical phenomena capable of affecting the entire planet or impinging in some detrimental way upon the global community. Such global geophysical events (GGEs) form a compendium of low frequency-high magnitude phenomena of which CAIs are just a single element. While far less well understood, and therefore scientifically much more controversial, terrestrial GGEs currently appear at least as hazardous as impacts of kilometer-sized and larger bolides, and to have frequencies that are considerably shorter than CAIs capable of comparable levels of destruction and disruption (Tables 6.1 and 6.2). A miniscule glimpse of this capability was provided by the December 26, 2004 Asian earthquake and tsunami, which claimed an estimated 250 000 lives (including 100 000 children), destroyed close to half a million buildings, and led to eight million people being made homeless, impoverished, displaced or unemployed.
Sometime in the foreseeable future, perhaps during this decade or maybe not until our great-great-grandchildren are adults, an asteroid the size of a large building will crash into the Earth’s atmosphere, exploding in an air-burst with the force of megatons or more of TNT. Most likely, such an event will happen over an ocean or sparsely populated desert; but, if it occurs over an urban area, the consequences could be very destructive and deadly. Actually, small strikes by cosmic grains of sand happen all the time (witness meteors or “shooting stars”, visible in a dark, clear sky several times an hour) and every year many large rocks, called “meteorites”, survive their atmospheric plunge to be collected and exhibited in museums.
The Earth is immersed in a swarm of Near Earth Asteroids (NEAs) capable of colliding with our planet, a fact that has become widely recognized within the past decade. The first comprehensive modern analysis of the impact hazard resulted from a NASA study requested by the United States Congress. This Spaceguard Survey Report (Morrison 1992) provided a quantitative estimate of the impact hazard as a function of impactor size (or energy) and advocated a strategy to deal with such a threat.
Over the last several decades, evidence has steadily mounted that asteroids and comets have impacted the Earth over solar system history. This population is commonly referred to as near-Earth objects (NEOs). By convention, NEOs have perihelion distances q ≤ 1.3AU and aphelion distances Q ≥ 0.983AU (e.g. Rabinowitz et al. 1994). Subcategories of the NEO population include the Apollos (a ≥ 1.0AU; q ≤ 1.0167AU) and Atens (a < 1.0AU; Q ≥ 0.983AU), which are on Earth-crossing orbits, and the Amors (1.0167AU < q ≤ 1.3AU) that are on nearly-Earth-crossing orbits and can become Earthcrossers over relatively short timescales. Another group of related objects that have not yet been considered part of the formal NEO population are the IEOs, or those objects located inside Earth's orbit (Q < 0.983AU). To avoid confusion with standard conventions, I treat the IEOs here as a population distinct from the NEOs. The combined NEO and IEO populations are comprised of bodies ranging in size from dustsized fragments to objects tens of kilometers in diameter (Shoemaker 1983).
Someday, in a not too far away future. A potentially hazardous astronomical object, with an estimated size significantly above 10 meters, is just detected. Quite soon, the probability of its impact with the Earth in, again, a not too far away future, is found to be close to 1. We certainly want to predict with a decent accuracy the effects of the impact and, even better, to tentatively initiate a mitigation strategy.
The space missions of the past decades have shown that impacts represent an ubiquitous phenomenon in the Solar System, and occur at all scales, from dust particles up to planetary bodies. In fact, a clue to the importance of this phenomenon also for our planet has always been available on the heavily cratered surface of the Moon, that testifies to the present and past fluxes of bodies on Earth crossing orbits.
Astronomical and geological investigations initiated in the past century have revealed that the Earth is continually subjected to the infall of a variety of solid solar system debris. Most of this debris is so small that it evaporates harmlessly, as it enters the Earth’s upper atmosphere at high speed. However, an occasional larger object survives atmosphere entry. Small examples of such objects result in meteorites on the surface of the Earth, with harmful consequences only for the rare individuals, who happen to be struck by them. More infrequent, but larger, objects can cause local or even global devastation. A recent report on the number and consequences of such impacts (Team 2003) proposes that the impact frequency can be computed as a function of the energy release, equal to the kinetic energy of the object before it strikes the Earth: $$
T_{RE} (years) = 110E_{MT}^{0.77}
The impact with the Earth's oceans of a relatively small meteoroid, ≈260-300 m diameter, having a mean density of 2,500 kg/m3 and mean velocity of 17.8 km/s, would vaporize and loft sufficient seawater to increase the global stratospheric content of chlorine by 3 ppbv and possibly cause an Antarctic "ozone hole.” Meteoroids of this size or comets having equivalent kinetic energies are estimated to strike the Earth's oceans about once every 29,000-40,000 years. A large, globally distributed ozone depletion is predicted to occur about two to four times less frequently, resulting from the a combination of increased chlorine content (10 ppbv chlorine every 75,000-110,000 yr), increased NOy content (10 ppbv every 75,000-186,000 yr), and increased water vapor content (4 ppmv every 66,000-95,000 yr). The meteoroid diameter required to cause a large globally distributed ozone depletion is in the range 390-660 m for an average density and impact velocity. These hypothesized ozone depletions are predicted to occur with sufficient frequency that it may be possible to detect past asteroid impacts by examining the UV damage to DNA of pollen grains retrieved from ice cores such as the Antarctic Dome C core dating to 740,000 B.P. Model calculations using the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM) to simulate coupled dynamics and chemistry in the altitude range 30-500 km confirm that oxides of nitrogen and water vapor lofted to altitudes above 70 km are rapidly dispersed horizontally. These simulations show that a large fraction of the injected NO and H2O survives the photochemistry of the upper mesosphere and thermosphere
and is transported to the stratosphere, with maximum ozone depletions occurring about three months following the impact.
Tsunamis belong to the long-period oceanic waves generated by underwater earthquakes, submarine or subaerial landslides or volcanic eruptions. They are among the most dangerous and complex natural phenomena, being responsible for great losses of life and extensive destruction of property in many coastal areas of the World’s ocean. The tsunami phenomenon includes three overlapping but quite distinct physical stages: the generation by any external force that disturbs a water column, the propagation with a high speed in the open ocean and, finally, the run-up in the shallow coastal water and inundation of dry land (Gonzalez, 1999). Most tsunamis occur in the Pacific, but they are known in all other areas of the World including the Atlantic and the Indian oceans, the Mediterranean and many marginal seas. Tsunami-like phenomena can occur even in lakes, large man-made water reservoirs and large rivers.
There is a concern that the world we know today will end in a global ecological disaster and mass extinction of species caused by a meteorite impact (Chapman and Morrison 1994; Chapman 2004). We are aware that rare large impacts have changed the face of our planet as reflected by extinctions at the Permian/Triassic (∼251 Ma; Becker et al. 2001), Triassic/Jurassic (∼200 Ma; Olsen et al. 2002) and Cretaceous/Tertiary (∼65 Ma; Alvarez et al. 1980) boundaries. Today astronomers can detect and predict the orbits of the asteroids/comets that can cause similar impacts. Yet, Tunguska, Meteor Crater-size and smaller meteorites that could cause local disasters are unforeseeable. However, while planning to avoid the next bombardment by cosmic bodies we can look at past interactions of human societies, environment and meteorite impacts to understand to what extent human cultures were influenced by meteorite impacts. The question is whether the past examples are relevant in the modern situation, but they are certainly useful. The Kaali crater field in Estonia, in that respect, is an excellent case study area for past human-meteorite interactions. Moreover, Kaali is not the only Holocene crater field in this region: in fact, during the last 10 000 years Estonia has been targeted at least by four crater forming impacts and there are five registered meteorite falls (Fig. 15.1). The two large craters, Neugrund and Kärdla, originate from 535 and 455 Ma, respectively (Suuroja and Suuroja 2000). cr]
The Earth’s atmosphere, ocean and land surface interact together to provide the environmental conditions to which life and society have become accustomed. Society has come to depend on these components working together to provide relatively stable (or at least regularly varying) and livable conditions that are conducive to growing and gathering necessary food, providing sufficient freshwater, limiting the domains and viability of disease vectors and, except on rare occasions, providing safe habitat for living and reproducing.
The nature of the bright bolide and the giant explosion that took place on June 30, 1908, in the Podkamennaya Tunguska river basin, Central Siberia, is still being discussed. The area with fallen trees is in excess of 2000 square km (Fast et al. 1967), whereas the kinetic energy deposited by the impactor has been estimated to be ca. 15 million tons of TNT equivalent (or 1500 Hiroshima bombs; Vasiljev 1998). Nevertheless, Kolesnikov et al. (1973) have shown that the explosion could not be of nuclear nature. Its energy release was, in fact, too big to be a nuclear explosion. Two other nuclear hypotheses, one of annihilation and one of thermonuclear origin, have been tested by measuring 39Ar activity in rocks and soil at the explosion epicenter. No excess 39Ar was detected, and this method is much more sensitive than the method of measuring radiocarbon in tree rings (Cowan et al. 1965). Likewise no excess beta activity was observed in 1908, or the following years, in two ice cores from Camp Century nor in an ice core from DYE-3, all three on the Greenland ice sheet (Rasmussen et al. 1984).
Longo G.: "The Tunguska event" . Chapter 18, pp. 303-330 in the book: "Comet/Asteroid Impacts and Human Society, An Interdisciplinary Approach, Bobrowsky, Peter T.; Rickman, Hans (Eds.)." , 546 p., © Springer-Verlag, Berlin Heidelberg New York, 2007
In the early morning of 30th June 1908, a powerful explosion over the basin of the Podkamennaya Tunguska River (Central Siberia), devastated 2 150 ± 50 km2 of Siberian taiga. Eighty millions trees were flattened, a great number of trees and bushes were burnt in a large part of the explosion area. Eyewitnesses described the flight of a fire ball, bright as the sun. Seismic and pressure waves were recorded in many observatories throughout the world. Bright nights were observed over much of Eurasia. These different phenomena, initially considered non-correlated, were subsequently linked together as different aspects of the Tunguska event (TE).
Depending on distance from the event - at (101° 53′ 40″ E, 60° 53′ 09″ N) - the Siberian catastrophe of 30 June 1908 was reported as cannon shots (barisal guns, brontides: Gold and Soter 1979) and/or storms followed by columns of fire, also described as lightning and thunderclaps, after which an area of more than 2000 square kilometers, diameter some 50 km, had its trees debranched, felled, or their tops chopped off, varying with their distance from the center and/or height above the valleys, even with islands of tree survival near the center, and in the valleys. A few tents (tepees), barns (storage huts), and cattle (reindeer) were damaged, hurled aloft, and/or incinerated. The haunting took some ten minutes, variously reported between 2 min and an hour; one man even washed in the bath house to meet the death clean.
It is important to differentiate between a natural hazard and a natural disaster. A natural hazard is an unexpected or uncontrollable natural event of unusual magnitude that threatens the activities of people or people themselves (NHERC 2004). A natural disaster is a natural hazard event that actually results in widespread destruction of property or causes injury and/or death. Only a very small fraction of the actual meteorite events are observed as falls in any given year. It has been predicted that 5800 meteorite events (with ground masses greater than 0.1 kg) should occur per year on the total land mass of the Earth. In a recent work, Cockell (2003) emphasizes the scientific and social importance of giving a coordinated and multidisciplinary response to events related with the entrance of small asteroidal bodies that could potentially collide with the Earth. In fact, it can be said that the recovery of small meteorites between 1 kg to 200 kg is relatively common; in Spain alone there are four meteorites in the collection of the National Museum of Natural History, weighing more than 30 kg (e.g. Colomera iron meteorite). But what would happen if the impact bodies, despite weighing up to 200 kg, would melt?
It would have been ridiculous, not too long ago, to admit openly that you were thinking about asteroids and comets slamming into the Earth. Such events could mean the end of the world as we know it - TEOTWAWKI as millenialists call it - and that kind of talk is often ridiculed. Then again, it would have been ridiculous, not too long ago, to think that two hijacked 767s would slam into the World Trade Center and make both towers fall. Thinking about NEOs is becoming more commonplace, although not entirely normal.
Perhaps the earliest studies of risk perception with regard to natural hazards were conducted by geographer Gilbert White (1945, 1964) and his students (e.g. Burton and Kates 1964). Later, in 1974, this author joined with White and economist Howard Kunreuther to review this early work in the context of new research in cognitive psychology (Kahneman and Tversky 1972; Tversky and Kahneman 1971, 1973) describing the idiosyncratic ways human minds think about probability, uncertainty and risk (Slovic et al. 1974). This research illustrated the workings of Herbert Simon’s theory of “bounded rationality” (1959), which asserts that human cognitive limitations force decision makers to construct a simplified model of the world in order to deal with it.
Estimation of the risk of any natural hazard is problematic when occurrences are very rare and predictions are based on sparse data. While some natural hazards are perceived as totally random phenomenon, in some cases improved monitoring techniques and models have heightened awareness and allowed for better disaster mitigation strategies (e.g. alerts, evacuations, long-term best management practices) to be implemented (e.g. Thouret et al. 1995; Wu and Sidle 1995; La Delfa et al. 2001). Volcanic eruptions are examples of hazards where improved techniques for monitoring dome growth, seismic conditions, air chemistry and even groundwater can help forecast the onset of a major eruption (e.g. Miller and Chouet 1994; Miyabuchi 1999; La Delfa et al. 2001). Now it is often the very infrequent hazards related to volcanic eruptions (e.g. pyroclastic flows, lahars, dome collapses) that inflict the most damage due to their lower predictability (Major et al. 2001; Reid et al. 2001; Sheridan et al. 2001). For most natural disasters, such 'secondary' hazards must be considered in hazard risk assessments and mitigation measures. Although it is known that the Earth has been impacted by asteroids in the past large enough to annihilate most life on the contemporary planet (Sleep et al. 1989; Pope et al. 1994; Tate 2000; Paine, 2001; Chapman 2004), many of these isolated occurrences remain undiscovered.
Until quite recently, research into comet and asteroid hazards was focused on establishing the scale and scope of past impacts, credible estimates of their recurrence, and models for physical impact scenarios. If there is still much to be done, the threat does seem convincingly demonstrated. CAI hazards have moved well beyond the realm of ungrounded speculation and apocalyptic visions. The results represent more than just new findings. They revolutionize, or are about to revolutionize, some basic understandings about the Earth, its history, biological evolution and future. Although human life has had a tiny place in the story so far, our longer term fate seems to be challenged by these forces and may be decided by them.
The possible influence of impacts of celestial bodies on the evolution of life on Earth has been brought to the attention of the scientific community in 1980, with the publication of a famous paper by Alvarez et al. (1980) on the event that caused the mass extinction at the boundary between the Cretaceous and the Tertiary, 65 million years ago.
It is important not to let the potential magnitude of the impact from a comet or asteroid impact (CAI) skew discussion. Without doubt the energy released, hence consequences, from an ocean or terrestrial impact would be very large (McGuire 1999, pp 231-235; McGuire et al. 2002, pp 133-158). An impact in the world ocean (approximately 71% of our planet's surface), could affect much of humanity living in large coastal cities and other coastal settlements. Recent trends in urbanization and migration to coastal areas have placed many hundreds of millions of people in harm's way (Wisner et al. 2004, Chap. 2 and 7). <1> A terrestrial impact on a heavily populated area is highly unlikely since humanity's cities cover such a very small percentage of the Earth's surface (only about 2-3%). Yet their ecological footprint is many times greater - 15 times as great in the case of greater Vancouver (Canada), 13 times in the case of the whole of the densely populated Netherlands (Wackernagel and Rees 1996). So in both the case of destruction of coastal cities by large tsunami and an impact on a major urban area, there arises the question of providing for survivors and displaced evacuees (if current or future tsunami warning systems can provide sufficient warning). The challenge of immediate relief (provision of water, food, shelter, sanitation, and medical assistance to survivors) following a tsunami produced by a CAI can be imagined by multiplying the logistical efforts required by the Asian tsunami (December 2005) or the impact of hurricane Katrina on New Orleans and the Gulf Coast (August 2005) by an order of magnitude.
On the evening of June 18, 1178, several witnesses near Canterbury, England saw a spectacular night sky event (Ingram 1999). These observers reported directly to a monk who was keeping detailed records of events occurring in or around Christ Church Cathedral. Fortunately, this diary, the Chronicles of Gervase has survived and provides a detailed description of the strange events of 1178:
This year, on the Sunday before the Birth of Saint John the Baptist, after sunset when the moon had first become visible, a marvellous phenomenon appeared to five or more men while sitting facing it. Now there was a bright new moon, and as usual the horns protruded to the east; and lo, suddenly, the upper horn split in two. From the middle of this division a firebrand burst forth, throwing over a considerable distance fire, hot coals and sparks. Meanwhile the body of the moon which was lower [than this] writhed as if troubled, and in the words of those who told this to me and who saw it with their own eyes, the moon throbbed as a beaten snake. It then returned to its former state. This phenomenon was repeated twelve times and more, the flame assuming various twisting shapes at random then returning to normal. And after these vibrations it became semi-dark from horn to horn, that is, throughout its length. Those men who saw this with their own eyes reported these things to me who writes them; [they are] prepared to give their word or oath that they have added nothing false to the above.
An asteroid or comet will threaten a major urban center sometime in the future. It is very unlikely to happen this year, but some day it will happen. The potential damage will be catastrophic. A typical property insurance policy promises coverage for damage caused by such an impact, but there are limits to the capacity of insurance to pay. Moreover, damage from an asteroid or comet strike in a major urban center does not fit the principles of insurance coverage, so insurers may use the months or years between detection and impact to exclude this peril in insurance policy renewals that take place before the strike occurs. National and international policy makers should develop preparedness plans assuming that they will manage society's recovery from an asteroid or comet strike in a major urban center, including responsibility for financial matters.
The objective of this paper is to investigate the economic consequences of asteroid or comet impacts, referred to here as near Earth objects (NEO). As of September 8, 2005, according to the Near Earth Objects Program of NASA (NASA 2005), there are 3535 NEOs, of which asteroids (NEAs) are 3438. NEAs greater than 1 km in diameter are represented by 797. The number of potentially hazardous asteroids (PHAs) is 720, of which PHAs greater than 1 km are 146. Of these, 3 appear (on September 8, 2005) on the NASA impact risk page. An NEO that is less than 50 meters would have a 5 megaton energy impact, although NEOs of even less than 30 meters could be damaging, depending on their composition and density. From about 50 meters to about 1 km diameter, an impacting NEO can do tremendous damage on a local scale. With an energy level above a million megatons (diameter about 2 km), an impact will produce severe environmental damage on a global scale. Still larger impacts can cause mass extinctions, such as the one that ended the age of the dinosaurs 65 million years ago (15 km diameter and about 100 million megatons). Table 29.1, reproduced from Chapman (Chap. 7 of this volume) is instructive; it summarizes impact energies and possible physical damages.
The first conscious recollection I have from my childhood was an aerial bombing. It was a beautiful summer afternoon in June 1940, in a small French village east of Paris. Fortunately no one in my family was hurt. During the following four years, with other children of my age, I was often pulled out from home and school by siren whistles announcing airplanes approaching. In none of these cases was there panic: the adults and children had been trained to react instantaneously and to seek refuge in vaulted cellars or in trenches.
Although scares associated with potential Earth impacts by specific comets and asteroids date back to quite early in the eighteenth and twentieth centuries, respectively (e.g. Marsden 2004), the era of modern impact scares is frequently considered to have begun with the 1997 XF11 incident in early 1998 (cf. Morrison et al. 2004). Both cited papers discuss that particular incident, as well as some subsequent scares, but in my opinion the second account contains errors. In fact, I published a very detailed discourse on 1997 XF11 several years ago (Marsden 1999a). That paper fully acknowledges that mistakes were made, by several people, in the manner the 1997 XF11 situation was handled at that time.
Astronomy may be the purest of sciences, but even astronomy must interface with the rest of society. First, society influences astronomy: Astronomical research is largely supported by public funds, and political priorities decide which of our favorite projects may become reality. And waste from human activity increasingly limits our ability to distinguish the faint signals from the Universe from such human-generated interference as light pollution, space junk, and radio noise from the ground and from space.
In the last six years, COSPAR has organized consecutively three NEOs-related meetings in its General Assemblies. The main purpose was to focus the attention of the scientific community to the potential impact hazards of NEOs to the global society. If we look back at the presentation materials in these meetings, they could be collected into several categories mirroring the responses on this critical issue. They are: (1) awareness of the threat; (2) analysis of the threat; (3) mitigation of the threat; and (4) utilization of the threat. The last item came about at the end of the NEOs session in COSPAR’s General Assembly in Paris on July 21, 2004. As a final round up of the meeting, several young scientists and PhD students were invited to a panel discussion on the study of NEOs in year 2030. Not surprisingly, the younger the researchers the more optimistic were their opinions. Instead of the roaming catastrophe brought about by an asteroidal or cometary impact, these young researchers were considering topics such as mining of the asteroids and how to build large-scale structures in space to accommodate such an enterprise. Perhaps there is a lesson to be learned here. As we have heard from a Chinese saying that crisis could also mean opportunity, it might be of interest to assess what are the benefits (instead of gloomy images) to be derived from the present discussions in this volume.
... The explosion, the most energetic since Tunguska, caused 1,500 injuries mostly from shattered glass. In Conway, Yeomans, and Rosenburg's History of Near Earth Objects Research, Tunguska takes up only 3 pages, and Chelyabinsk 2, of a 400 page book-one indication of the scope of the issue both in the past and for the future, not just for scientists but for society at large (Bobrowsky and Rickman, 2007). Funded and published by NASA, the book is a collaboration among the historian at NASA's Jet Propulsion Laboratory (JPL), Erik Conway; astronomer Don Yeomans who was deeply involved in Near Earth Object (NEO) science at JPL; and Meg Rosenburg, a planetary geophysicist who has researched cratered errains on the Moon. ...
... The explosion, the most energetic since Tunguska, caused 1,500 injuries mostly from shattered glass. In Conway, Yeomans, and Rosenburg's History of Near Earth Objects Research, Tunguska takes up only 3 pages, and Chelyabinsk 2, of a 400 page book-one indication of the scope of the issue both in the past and for the future, not just for scientists but for society at large (Bobrowsky and Rickman, 2007). Funded and published by NASA, the book is a collaboration among the historian at NASA's Jet Propulsion Laboratory (JPL), Erik Conway; astronomer Don Yeomans who was deeply involved in Near Earth Object (NEO) science at JPL; and Meg Rosenburg, a planetary geophysicist who has researched cratered errains on the Moon. ...
... It is most important to obtain such estimates for the current stage of geological history, i.e. for the Holocene (the last 10-12 thousand years). The existing estimates, which are used by the community of astronomers and astrophysicists, are based mainly on observations of comets and asteroids, as well as analysis of craters on the Moon and other bodies of the Solar System [8,9] . However, the most reliable data on the probabilities of cosmic bodies falling to the Earth can be obtained from an analysis of the actual statistics of such falls, provided that ground tracks are reliably recorded and there is reliable evidence of their connection with cosmic bodies [10] . ...
An expeditionary study of the area of the alleged impact event that occurred on 3.08.1993 in the area of the Lower Konkuli River (southeast of the Aldan Highlands, Lurikan Range, Russia) was carried out. According to the materials of remote sensing, the places of collision with the earth of a cosmic body are determined. In the area of the impact of the shock wave on the Earth's surface, peat samples were selected, the micro probe analysis of which showed the presence of a cosmogenic substance in concentrations 6-8 times higher than the background. Silicate and magnetite micro spheres, native iron, moissanite, and carbon micro tubes coated with a film consisting of pure nickel were found. Of particular interest were the findings of specific Ni film micro structures that allow us to make an assumption about the cometary nature of the Uchur cosmic body. Most researchers associate the observed flights of fireballs with the subsequent fall of meteorites. Researchers are trying to find the massive body of the fallen space body. However, often, even after many years of searching, a massive cosmic body cannot be found. This happened when studying the site of the fall of the Tunguska cosmic body. In this case, it remains to be assumed that the cosmic body contained microscopic dust particles. The structure and composition of such particles can only be studied using microscopic research methods. When studying the Uchur cosmic body, the authors concluded that it could be of a cometary nature due to the findings of specific particles-thin films of pure nickel on the surface of plant remains of terrestrial origin. This hypothesis arose from the recent discovery of atomic nickel vapors in comets.
... It is most important to obtain such estimates for the current stage of geological history, i.e. for the Holocene (the last 10-12 thousand years). The existing estimates, which are used by the community of astronomers and astrophysicists, are based mainly on observations of comets and asteroids, as well as analysis of craters on the Moon and other bodies of the Solar System [8,9] . However, the most reliable data on the probabilities of cosmic bodies falling to the Earth can be obtained from an analysis of the actual statistics of such falls, provided that ground tracks are reliably recorded and there is reliable evidence of their connection with cosmic bodies [10] . ...
An expeditionary study of the area of the alleged impact event that occurred on 3.08.1993 in the area of the Lower Konkuli River (southeast of the Aldan Highlands, Lurikan Range, Russia) was carried out. According to the materials of remote sensing, the places of collision with the earth of a cosmic body are determined. In the area of the impact of the shock wave on the Earth’s surface, peat samples were selected, the micro probe analysis of which showed the presence of a cosmogenic substance in concentrations 6-8 times higher than the background. Silicate and magnetite micro spheres, native iron, moissanite, and carbon micro tubes coated with a film consisting of pure nickel were found. Of particular interest were the findings of specific Ni film micro structures that allow us to make an assumption about the cometary nature of the Uchur cosmic body. Most researchers associate the observed flights of fireballs with the subsequent fall of meteorites. Researchers are trying to find the massive body of the fallen space body. However, often, even after many years of searching, a massive cosmic body cannot be found. This happened when studying the site of the fall of the Tunguska cosmic body. In this case, it remains to be assumed that the cosmic body contained microscopic dust particles. The structure and composition of such particles can only be studied using microscopic research methods. When studying the Uchur cosmic body, the authors concluded that it could be of a cometary nature due to the findings of specific particles—thin films of pure nickel on the surface of plant remains of terrestrial origin. This hypothesis arose from the recent discovery of atomic nickel vapors in comets.
... ! That they may have broken off after water accumulated on an airplane fuselage, or were produced from airplane toilet leakage is not probable as megacryometeors have been observed and recorded in the mid 1800s, long before the invention of airplanes, and as the chunks of ice that occasionally leak from airliner toilets are distinctly blue due to the disinfectant used (Beech, 2006;Bobrowsky & Rickman, 2007). ...
Ice meteors have been reported falling form the skies since the 19th century. The consensus of opinion is they are not meteors at all, but formed under unusual atmospheric conditions effecting the troposphere. Some scientists believe, however, that ice meteors, i.e. Megacryometeors, have an extraterrestrial origin. A review of the literature and arguments pro and con regarding the possible origins of megacryometeors is presented, as well as new data on a ice meteor subjected to electron microscopic, isotope ratio and tritium analysis. The results favor an extraterrestrial origin. Although admittedly speculative, based on this data and a review of the literature, the authors theorize this particular megacryometeor may have originated from Saturn's E ring, or from the surface of Saturn's moon Enceladus.
Environmental processes and phenomena pervade the planet, affecting day‐to‐day and decade‐to‐decade lives and livelihoods. When they are associated with death and destruction, they are seen as environmental hazards. Defining “environmental hazards” followed by classifying them into astronomical, biological/ecological, geological, and hydrometeorological sets the stage for examining human influences on environmental processes and phenomena, especially illustrating how human activity leads environmental processes and phenomena to become hazardous. Overlaps and connections among the four categories are explored, including cascading hazards, coincidental hazards, and the hazard influencer of climate change. The final section explains the importance of living with environmental hazards rather than trying to oppose or combat them, showing how society can use knowledge of environmental processes and phenomena to avoid harm while garnering advantages.
In 1908, thunderous blasts and blazing fires from the sky descended upon the desolate Tunguska territory of Siberia. The explosion knocked down an area of forest larger than London and was powerful enough to obliterate Manhattan. The mysterious nature of the event has prompted a wide array of speculation and investigation, including from those who suspected that aliens from outer space had been involved. In this deeply researched account of the Tunguska explosion and its legacy in Russian society, culture, and the environment, Andy Bruno recounts the intriguing history of the disaster and researchers' attempts to understand it. Taking readers inside the numerous expeditions and investigations that have long occupied scientists, he foregrounds the significance of mystery in environmental history. His engaging and accessible account shows how the explosion has shaped the treatment of the landscape, how uncertainty allowed unusual ideas to enter scientific conversations, and how cosmic disasters have influenced the past and might affect the future.
本文 主 要讲 述 各类 金属 质 小行 星 在轨 处置 前 沿技 术 ，对 核 爆打 击
技术 、 动能 撞 击技 术、 引 力牵 引 技术 等 8 种 在 轨处 置 技 术开 展 研究 ，
分 析 不 同 处 置 技 术 的 发 展 成 本 、 效 能 、 技 术 成 熟 度 以 及 场 景 适 用 性 。
其中 ，本 文还 基 于 动能 撞 击技 术 ，利 用物 质 点法 模 拟了 撞击 器 以不 同
速度 、角度 撞 向金 属质 小 行星 的 防御 过程 ，分析 撞 击器 防御 效 果。小
行星 采 用 了 JC 强度 模型 和 Gruneisen 状 态方 程，撞 击器 采 用 simJC 强
度模 型、Gruneisen 状态 方 程 及 PlaStrain 失 效 模型。结 果显 示，对于
等效 直 径 在 10-20m 的金 属 质小 行 星， 在超 高 速撞 击 作用 下， 撞 击器
完全 碎 裂 ，小 行 星 部分 碎 裂 ，大 部 分 碎片 以 与撞 击 方向 相反 的 速度 向
外喷 射 ，提 高 了小 行星 的 偏移 效 率。
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