Asteroid  Extinction / Short Timeframe

Asteroid  Extinction / Short Timeframe

Extinction level event could come at any time

Though collisions with larger bodies are much less frequent now than in the early stages of planet formation in the Solar System, they do still occur. Very significant events, capable of causing damage at the surface, will happen on scales of a few hundred to a thousand years. But we do not know when the next impact of an object of sufficient size to cause widespread devastation at ground level may occur. At the current state of knowledge, it is about as likely to happen next week as in a randomly selected week a thousand years from now. The Survey In an effort to gain better understanding of this hazard, NASA has been conducting a search of space near the Earth's orbit to understand the population of objects that could do significant damage to the planet should there be a collision. Commonly referred to as the "Spaceguard Survey", NASA's Office of Space Science conducts this research effort on "Near Earth Objects (NEOs)" -- that is, asteroids and comets that come within an astronomically close distance, <50 million kilometers of Earth. The objective of this survey is to detect, within a 10-year period, at least 90% of the NEOs that are greater than 1 kilometer in size and to predict their orbits into the future. The survey officially started in 1998 and to date, over 700 objects of an estimated population of about 1100 have been discovered, so the effort is believed to now be over 70% complete and well on the way to meeting its objective by 2008. A few words of explanation on the parameters and limitations of the survey may be appropriate. The threshold of 1 kilometer in size was accepted for this survey because it is about the size asteroid that current research shows would border on having a devastating worldwide effect should an impact occur. Because of the orbital velocities involved, impact on Earth of an asteroid of this size would instantly release energies calculated to be equivalent to the detonation of almost a 100,000 megaton nuclear device, i.e., more than all the world's nuclear arsenals detonated at the same time. Not only would the continent or ocean where the impact occurs be utterly devastated, but the effects of the super-heated fragments of Earth's crust and water vapor thrown into the atmosphere and around the world would adversely affect the global weather for months to years after the event. Such an event could well disrupt human civilization anywhere from decades to a century after an impact.

Asteroid  Extinction / Inevitable

Extinction-causing asteroid strike is inevitable

Smith ‘2k (Donald Smith, December 20, 2000, National Geographic News, “Getting Serious About Asteroid Strikes,” http://news.nationalgeographic.com/news/2000/12/1220_asteroid.html)

The early space program gave us an image of Earth as a lustrous blue pearl, serenely sailing through space. But a more accurate metaphor might be a goose in hunting season, flying though a hail of bullets. Earth orbits amidst a swarm of potentially threatening asteroids, some large enough to cause a planet-wide disaster should there be a collision. Chances of such a collision are small in the short-term, but inevitable over time, scientists say. The asteroid strike that ended the age of dinosaurs whalloped Earth 65 million years ago at what is today Mexico’s Yucatan Peninsula. However, as recently as 1986, a dangerous asteroid came within six hours of striking Earth, although no one realized how close Earth had come to disaster until much later. “These things have hit the earth in the past, and they will hit the earth in the future,” warned Eugene Shoemaker, the space-probing geologist who first alerted the world to the danger of near-earth asteroids (NEAs) before he died in 1997. “The catastrophe will exceed other natural disasters by a long shot.” The asteroid that ended the age of dinosaurs was at least six miles (10 kilometers) wide, but smaller asteroids can still be devastating. Scientists estimate that the impact of an asteroid with a diameter of one kilometer (0.6 miles) or more could kill at least a quarter of the world’s human population, as well as many other life forms. Less than a century ago a space rock only 330 feet (100 meters) wide exploded over Siberia. It leveled more than a half million acres (2,000 square kilometers) of forest. However remote, the possibility of the end of life as we know it has energized the astronomical community. The search for new asteroids, once considered the realm of space fanatics, has become serious science. OUT THERE Images of the night sky, as seen through powerful telescopes at California’s Palomar Observatory and elsewhere around the world, are systematically sifted for evidence of yet undiscovered threats. Each object that doesn’t look like an asteroid is carefully removed. The process is painstaking. So far only about half of the estimated 1,100 asteroids with a potential for a catastrophic impact with Earth have been discovered. British astronomers recently urged their government to become more actively involved in the effort.

Asteroid  Impact Winter

Impact winter form an asteroid outweighs nuclear winter

Marusek ‘7 (James, nuclear physicist & engineer, American Institute of Aeronautics and Astronautics, “Comet and Asteroid Threat Impact Analysis,” http://www.aero.org/conferences/planetarydefense/2007papers/P4-3--Marusek-Paper.pdf)

It has been theorized that the impact of a large comet or asteroid and the resulting fires would throw up so much dust and ash in the stratosphere that it would shut off sunlight from the surface of the planet. This would plunge the Earth into a period of darkness lasting many months and even years. In the absence of sunlight, solar heating of the Earth’s surface would come to a halt. This will lead to a severe cooling of the continents approximately 70°F (39°C) below normal and lead to an "impact winter".2 An "impact winter" is similar to a "nuclear winter" but more severe, and could lead to a new Ice Age.

Asteroid strike causes impact winter

Marusek ‘7 (James, nuclear physicist & engineer, American Institute of Aeronautics and Astronautics, “Comet and Asteroid Threat Impact Analysis,” http://www.aero.org/conferences/planetarydefense/2007papers/P4-3--Marusek-Paper.pdf)

The blast will eject debris into the upper atmosphere and into space in a ballistic trajectory. At impact, the comet or asteroid will be instantly vaporized along with material from the impact crater/cavity. The diameter of crater/cavity created will typically be 20 times the diameter of the impactor. This debris will be heated to temperatures exceeding 9,000°F (5,000°C).‡‡ The debris following a ballistic trajectory will reach the other side of the planet in 45 to 60 minutes.2 The debris from a large impactor will blot out the sun, the moon and the stars and turn the Earth dark as night. The vaporized rock cloud will rapidly cool and condense in space and form droplets that solidify into spherules (tiny glass beads about 1 mm in diameter). Over the next several hours and days, much of this debris will rain back down over the entire surface of the Earth. This returning debris will be fairly light and will be slowed significantly as it falls through the atmosphere and should not present a significant secondary impact hazard. The area around the impact site will become a major debris field. Some of this debris may be the size of large boulders. Massive debris will be deposited over short distances within the atmosphere. The debris field will taper off as a function of distance from point-of-impact. This debris will cause extensive damage. Whereas an ocean impact will create a vast amount of superheated steam, an impact on land will eject significantly greater solid debris into the atmosphere.

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