the very short-term continuation of our species. Well known are the many films and books devoted to elucidating the damage that would be done to civilizations by the blasts of such weapons. However, few people have explored, at least in any great detail the effects on our planets ecosystem by a nuclear blast.
Most researchers who focus on climatic changes throughout history explain that a change in just a few degrees can and will have lasting planet wide effects-most of these effects are detrimental to life-including human life. One theory suggests that a nuclear exchange would prompt a "nuclear winter." Dr. Carl Sagan and others introduced this idea in 1983 in the journal Science. In this theory, after the explosions of a nuclear exchange have stopped, the real lasting damage will be just beginning. The spread of ash and smoke in the atmosphere from global fires, will block sunlight, darkening the sky, which will lead to lower global wide temperatures of as much as 10-15 degrees centigrade within 5-6 months. The most conservative models show that a change in the temperature of even one degree Centigrade would unbalance the ecosystem, thus directly affecting the survival of many species on Earth, including humanity.
These theories of the effects of all this smoke and ash in the atmosphere are more than an idle theory-a very similar event has happened several times on our planet, the last, being some 65 million years ago. In 1979, Walter Alvarez was sifting through sediments from Gubbio, Italy when he discovered a large amount of a radioactive element that is rare on Earth-but is found in meteors and asteroids. This material called iridium was found in sediments dating to the boundary between the Cretaceous and Tertiary periods, called the K-T boundary. This iridium did not have a terrestrial explanation. Alvarez's research gave support to an already proposed asteroid theory of vast extinctions that have occurred for the past 400 million years or so. We now know that an asteroid, roughly the size of Mount Everest, slammed into what is today the Yucatan Peninsula of Mexico. About once every 30 to 60 million years, something devastating occurs on our planet. As we slowly revolve around our galaxy, our tiny solar system is brought into contact with other space debris, including comets, asteroids, and other objects, both large and small. In addition, every now and then, one of these astral bodies slams into our planet. The resulting devastation from a moderate sized impact is an almost total loss of life on our world. This has occurred about five times in Earth's history. These mass extinctions are what led to the rise of our own species: humanity. Before the impact that led to the extinction of the dinosaurs, which had dominated Earth for more than 150 million years, mammals were small, nocturnal, and secretive. They needed to spend most of their time and energy in evading meat-eating dinosaurs. With the extinction of dinosaurs, the remaining mammals moved into habitats and ecological niches previously dominated by the dinosaurs. Over the next 65 million years, these early mammals evolved into a wide variety of species, assuming many ecological roles and rising to dominate the Earth as the dinosaurs had before them.
The first of these Global Killers slammed into our planet around 440 million years ago in what is known as the Ordovician Period. Because of this impact, the fossil record shows that nearly 90 percent of all the species on Earth became extinct. The second event took place 370 million years ago, near the end of the Devonian Period, which resulted in the loss of over 80 percent of all species. The third and greatest mass extinction, at least so far, happened around 245 million years ago, at the end of the Permian Period. Soon after this enormous impact, nearly 96 percent of all species on Earth were lost. This devastation was so incredible, that paleontologists use this event to mark the end of the ancient, or Paleozoic Era, and the beginning of the middle, or Mesozoic Era, when many new groups of animals evolved. Just over 205 million years ago, near the end of the Triassic Period, the fourth mass extinction claimed over 75 percent of the species alive at the time, including a large number of amphibians, fish and reptile species. The fifth, most well known, and most recent major collision occurred just over 65 million years ago, and would end the Cretaceous Period. This collision with an asteroid resulted in the loss of 75 percent of all species, including the giant marine reptiles, and, the dinosaurs.
This last impact is known to have produced a spray of debris called an ejecta sheet, which was blown from the edge of the crater. This is surmised because traces of an element, common to asteroids called Iridium, has been found over vast regions of North and South America. In fact, material from the impact's explosion was distributed all over the Earth. Although the large amounts of ash in the geological strata suggest that most of North and South America were devastated by fire from the impact, the long-term planet-wide environmental effects were ultimately more deadly. Dust from the impact blocked sunlight from the earth's surface for many months, while sulfur ejected from the impact site, combined with water vapor and chlorine, from the oceans that were flash boiled, and nitrogen from our air produced a worldwide downpour of intense acidic rain. The darkness and acid rain caused plant growth to cease. As a result, both the herbivorous dinosaurs, which were dependent on plants for food, as well as the carnivorous dinosaurs, which fed on the herbivores, died out. On the other hand, animals such as frogs, lizards, and small insect-eating turtles and mammals, which were dependent on organisms that fed on decaying plant material, were more likely to survive.
When this piece of rock struck the Earth it was traveling about 30,000 miles per hour. The resulting impact caused fires on a global scale due to the enormous heat. This would explain the iridium deposits and the fires would explain a surplus of carbon that has also been discovered at the K-T boundary layer. Other researchers studying carbon deposits in sedimentary layers have documented a period in Earth's past when ancient wildfires were widespread. Fossils in the sediments in the K-T boundary also show a strange disappearance of about 60 percent of the animals and plants in this period of time-nearly all animals weighting over a few dozen pounds were wiped out. These ancient fires may provide evidence from Earth's past that give us an idea of how a nuclear war climate might affect the climate. It would be hard to prepare for the striking of an asteroid, however, the threat from a similar event, the detonation of several thermonuclear devices would almost certainly cause similar global destruction.
What about a much feared "all out thermonuclear exchange" implementing tens of thousands of weapons? We strangely enough have a reasonable facsimile to such a catastrophe-the planet Mars. In 1984, a meteorite, later christened ALH84001U, was found in Antarctica. This meteorite, which originated about 4.5 billion years ago on Mars, contained what appear to be fossilized microorganisms, along with other traces of life. The ramifications of these discoveries cannot and must not be dismissed. Life on Earth first appeared about 3.8 billion years ago, at a time when it is believed the planets formed. Mars is almost exactly the same age as Earth, and most probably had the same reducing atmosphere. Observed astronomical evidence is fully consistent with the occurrence of microorganisms on a cosmic scale, in both meteorites as well as comet dust. This may seem at first, unbelievable, however the relative comparisons between the early planetary development of both Mars and the Earth were very similar. One catastrophic event ensured that no higher life would develop on the Red Planet. In the newly published book, Many Worlds, which includes many of the brightest writers and scientists in their fields, and is edited by the renown historian, scientists and author, Stephen J. Dick, there is a section by Christopher P. McKay titled "Astrobiology: The Search For Life Beyond The Earth." On page 51 of Many Worlds, there is a small chart comparing the development of the two planets between 4.5 Billion years ago and today. At some point, about 3.3 billion years ago, some catastrophic event, most probably a huge asteroid collision, snuffed out any beginnings of life. The event would have been far greater than Earth has experienced, thus putting an end to any microbiological life that had begun. The likely candidate is the impact of an asteroid or small moon, causing the crater Hellas Planitia. This crater dwarfs any that have been found on our own planet, measuring 1,243 miles wide and nearly four miles deep. Because of this enormous impact, the process of life would have to be halted. There would be no development of organisms that give off oxygen as a waste product, as on our planet. No more atmosphere of any kind would remain, for it would have been blasted into space by the shock wave. The tremendous heat from the impact would have boiled most of the liquid water away-what remained would be frozen solid by the impending winter.
The crater of the object that formed the KT boundry left a relatively small crater, about 112 miles in diameter, yet its impact leveled most of North and South America's vast forests. As destructive as that rather small impact was, what should happen if an asteroid the size of the rock that formed the Hellas crater hit Earth? That answer is quite simple: there would be no life on Earth today, not even microbes. Humanity currently has in its possession, enough weapons to reproduce such an event. Bomb shelters would be useless. No shelter could withstand such blasts, and if anyone could survive the initial air bursts, radiation, acid rains, plumeting tempersatures, lack of food and drinkable water, the devastation of approximately millions of megaton detonations would destroy all life on our planet. The forests, planet wide, would be rapidly burned to dust by the blast front that would be traveling many times the speed of sound. The heat from the blast front would erase any trace of humanity. Much of the ocean would be heated to the point that oxygen maturation would be unable to support life. Massive earthquakes would contort and twist our planet; volcanic eruptions would begin simultaneously around the globe. However, no creature would be here to know. Between the heat flash, acid rains, radiation and first rising, then quickly dropping temperatures, the Earth would enter into what could be a permanent ice age. The physical planet would go right on spinning at 900 miles an hour. It would still move along with the sun and other planets at over a million miles a day around our tiny galaxy. Nevertheless, life, even the hardiest bacteria or virus, would be utterly eradicated. Some time latter, I would guess about 12-18 months, the dust would settle, and the Earth would be left an arid and cold brown ball. Certainly fossils would exist that would show some alien visitor that we were here, but little else would define planet Earth as the once home of a reasonably advanced civilization. A civilization that had chose, rather than to put aside petty grievances, to self-destruct.