The Chicxulub collision was more powerful than one billion<\/strong> Hiroshima bombs and left a crater more than 100 miles in diameter, now mostly covered by the Gulf of Mexico.<\/p> While there are a variety of collolary theories regarding other environmental stresses that led up to or followed the impact, the scientific consensus to-date is that this was what triggered the mass extinction that ended the reign of the dinosaurs. Sedimentation layers around the world that correspond to the time of the impact have much higher concentrations than normal of iridium, an element that is rare in the Earth’s crust and relatively abundant in asteroids and comets.<\/p> The impact itself would have generated dust clouds and sulfuric aerosols that blocked the Sun’s light and devastated plant life. This triggered a catastrophic collapse in the food chain. We have also found evidence for the tsunamis generated when the asteroid hit the water, such as marine sand in places where there were no seas, at the time. The heat pulse from the impact and the re-entry of debris cast out into space would have also ignited firestorms across the planet, dumping pollutants into the atmosphere.<\/p> Even if there were multiple impacts that triggered other calamities, as some scientists suggest, the Cretatious-Tertiary extinction event stands as a lesson for us in the fundamental value of having both knowledge and understanding of the workings of our solar system. As one science fiction author once astutely put it, the dinosaurs died because they didn’t have a space program<\/strong>.<\/p> A study of Earth’s geological record will show the evidence of past impacts, some perhaps even larger than that which killed the dinosaurs. An asteroid or comet impact is believed by some scientists to have played a role in the immense Permian-Triassic extinction event 250 million years ago, though we are much less certain about its causes.<\/p> However, we do know that 96% of all marine species and 70% of land-based vertebrates were wiped out. The Permian extinction is also the only known mass extinction of insect species.<\/p> In more recent times, we have actually observed dramatic collisions between asteroids and comets and other planets in our solar system. Perhaps the most notable example is from July 1994, when Comet Shoemaker-Levy 9 was seen striking Jupiter after having been broken up by the planet’s immense gravitational influence.<\/p> The actual impacts occurred on a side of Jupiter pointed away from Earth at the time. The Galileo probe, though, was already en route to Jupiter for its planetary science mission and observed the collision as it happened. The first impact created a fireball of nearly 43,000 degrees Fahrenheit and with a plume nearly 2000 miles high. The Hubble Space Telescope even saw the fireball plume rise over the edge of Jupiter’s visible disc.<\/p> Twenty-one impacts were observed over six days. The largest created a dark spot in Jupiter’s clouds approximately the diameter <\/strong>of the Earth and released energy equivalent to 600 times all of the nuclear weapons on the planet – combined<\/strong>.<\/p> Closer to home, the Tunguska event of 1908 is believed to be an airburst of an asteroid or comet fragment a few miles above the surface of the Earth. The blast was likely equivalent to the most powerful thermonuclear weapons ever built – between 10 and 30 megatons <\/strong>of TNT – and destroyed over 800 square miles of Siberian forest. Such an impact could easily devastate a metropolitan area.<\/p> Asteroids and comets, of which over 1000 are classified as “Potentially Hazardous Objects,” are not our only worry, though. The Ordovician extinction, approximately 440 million years ago, is theorized by some scientists to have been caused by a gamma ray burst from a relatively nearby supernova.<\/p> In such an event, one study showed that a 10-second<\/strong> gamma ray beam could destroy half of the Earth’s ozone and expose life on the surface to intense prompt UV radiation. Following the event, the Earth would be vulnerable to increased absorption of solar radiation, as well. This could have catatrophic effects on the food chain, because of mass die-offs of plants and plankton, and lead to widespread disruption of the biosphere.<\/p> Human beings tend to cluster in groups for mutual benefit and survival. It is an evolutionary strategy that usually works well for us. However, there are always a few who break out on their own to explore new areas and establish new groups. Most do not succeed. However, those that do ensure the continued survival of our species and introduce tremendous growth.<\/p> If fact, I would argue that the United States itself is a perfect example of that. Our nation was founded by people who left the Old World behind to start anew and make something special for themselves. That is how the original Thirteen Colonies were started. That is how “the West was won.” As a nation, we have been at our best when we are out on the frontiers.<\/p> Now, we live in a world with a globalized economy. The leadership of the United States is in question. History is starting to repeat itself. Like many great nations before us, we are becoming fat and complacent, more concerned with entertainment than accomplishment. However, we still have advantages in resources and ingenuity.<\/p> I can think of no more fitting legacy for the United States than to lead the way in what Gerard K. O’Neill, physicist and space advocate, called “the High Frontier.” The problems of space travel, asteroid and comet deflection, and the colonization of other worlds are immense. We are, quite literally, just scratching at the surface.<\/p> The balance here on Earth is tenuous, though. Every human being that has ever lived and died has done so here on this planet. All of our proverbial eggs are in one basket. There are many threats to that balance from within, such as global climate change, natural disasters, and our own propensity for violent political and economic struggle. We cannot assume that our fortune at living in a time relatively conducive to human civilization will continue indefinitely.<\/p> Just as the United States escaped the majority of the devastation of World War II to become the world’s technological and economic powerhouse, I think it likely that our descendants on other worlds will one day be called to do the same by avoiding calamity here on Earth.<\/p> So, what role is there for the government in all of this? That will be the subject of Part II.<\/p> Cross-posted at A World With No Boundaries<\/a>.<\/em><\/p>","protected":false},"excerpt":{"rendered":" There is a strong sentiment held by some these days that America doesn’t necessarily need to explore space or that, if it does, we should leave it entirely to the private sector. I’d like to discuss why I think space … Continue reading ![\"blog](\"http:\/\/contribute.chron.com\/ver1.0\/Content\/images\/store\/0\/14\/209193e9-1a3e-4d95-9ead-89f8ad1f76af.Full.jpg\")
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Artist’s rendition of the Chicxulub impact (NASA)<\/em><\/p><\/a>
Hubble Space Telescope imagery of the fireball (NASA)<\/em><\/p><\/a>
Artist’s rendition of a gamma-ray burst (NASA)
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Put simply, there are things out there in space that can kill us and our only defense is to go out there, study and understand those threats, and develop strategies for mitigation.<\/p><\/a>
Artist’s rendition of an exploration mission to an asteroid (NASA)<\/em><\/p>