LEWIS 1996 - professor of planetary science at the University of Arizona's Lunar and Planetary Laboratory (John S., Rain of Iron and Ice, p. 183-222)
The cost of finding and tracking two-thousand-plus kilometer-sized bodies that cross Earth's orbit is a few million dollars per year. Every estimate of the cost/benefit ratio that I have seen indicates that this is a wise investment. Developing a nearly complete catalog of these larger bodies is also clearly technically feasible, since such large bodies are relatively bright and relatively easily found. In fact, we have located about 10 percent of them already. In down-to-Earth terms, kilometer-sized bodies are global killers: they take die lives of a billion people per impact, and strike with explosive powers of one hundred thousand megatons at a mean rate of four impact events per million years. Thus the long-term average death rate from impacts is four billion people per million years, or four thousand people per year worldwide. The people of the United States make up about 5 percent of the global population, so the average American death rate from global-scale impacts is about two hundred per year. The death rate of American citizens from commercial aircraft crashes is one hunched people per year. The problem with finding and tracking these very large bodies is that evacuation docs not work: the effects of the disasters are global. The leading cause of death is probably famine induced by climate change. If such a body hits Earth, there are no refuges to which people can be relocated. Moving away from the computed impact area means selecting a slow death over a quick one. The death toll would be very little affected by any plausible relocation effort, since Earth's ability to support life would be universally diminished. Finding, tracking, and predicting the orbits of kilometer-sized bodies is neither technically demanding nor fiscally draining; rather, the problem arises when we ask what we would do with the knowledge. We can in fact do nothing meaningful to avoid this threat unless we use space technology to divert or destroy the threatening objects. The prospect of letting one hit our densely populated planet is unacceptable. The scarcity of life in the universe proves both the probability and impact of our advantage
KAZAN 2011 (Casey, Owner of Galaxy Media LLC and graduate of Harvard University, “Tracking the Realtime Threat of Near-Earth Asteroids &comets- could it save the planet?”, The Daily Galaxy, Feb 8, http://www.dailygalaxy.com/my_weblog/2011/02/tracking-the-realtime-threat-of-near-earth-asteroids-will-it-save-the-planet.html)//DT
Stephen Hawking believes that one of the major factors in the possible scarcity of intelligent life in our galaxy is the high probability of an asteroid or comet colliding with inhabited planets. We have observed, Hawking points out in Life in the Universe, the collision of a comet, Schumacher-Levi, with Jupiter, which produced a series of enormous fireballs, plumes many thousands of kilometers high, hot "bubbles" of gas in the atmosphere, and large dark "scars" on the atmosphere which had lifetimes on the order of weeks. Shoemaker-Levy 9 was the first comet discovered to be orbiting a planet, Jupiter, instead of the sun. This enlargement of a 1993 Hubble Space Telescope image above shows the brightest nuclei in a string of approximately 20 objects that comprise Shoemaker-Levy 9 as it hurtled toward its July I994 collision with Jupiter. It is thought the collision of a rather smaller body with the Earth, about 70 million years ago, was responsible for the extinction of the dinosaurs. A few small early mammals survived, but anything as large as a human, would have almost certainly been wiped out.Through Earth's history such collisions occur, on the average every one million year. If this figure is correct, it would mean that intelligent life on Earth has developed only because of the lucky chance that there have been no major collisions in the last 70 million years. Other planets in the galaxy, Hawking believes, on which life has developed, may not have had a long enough collision free period to evolve intelligent beings. While NASA's Wide-field Infrared Survey Explorer, or WISE, is busy surveying the landscape of the infrared sky, building up a catalog of cosmic specimens -- everything from distant galaxies to "failed" stars, called brown dwarfs, closer to home, the NEOWise mission is picking out an impressive collection of asteroids and comets, most of these hang out in the Main Belt between Mars and Jupiter, but a small number are near-Earth objects -- asteroids and comets with orbits that pass within about 48 million kilometers (30 million miles) of Earth's orbit. By studying a small sample of near-Earth objects, WISE will learn more about the population as a whole. How do their sizes differ, and how many objects are dark versus light. "We are taking a census of a small sample of near-Earth objects to get a better idea of how they vary," said Amy Mainzer, the principal investigator of NEOWISE, a program to catalog asteroids seen with WISE. So far, the mission has observed more than 60,000 asteroids, both Main Belt and near-Earth objects, with more than 11,000 are new previously unknown objects. "Our data pipeline is bursting with asteroids," said WISE Principal Investigator Ned Wright of UCLA. "We are discovering about a hundred a day, mostly in the Main Belt." About 190 near-Earth asteroids have been observed to date, of which more than 50 are new discoveries. All asteroid observations are reported to the NASA-funded International Astronomical Union's Minor Planet Center, a clearinghouse for data on all solar system bodies at the Smithsonian Astrophysical Observatory in Cambridge, Mass.