NRC 2010 (National Research Council Committee to Review Near-Earth Object Surveys and Hazard Mitigation Strategies, “Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies,” http://www.nap.edu/catalog.php?record_id=12842)
Ground-based telescopes have difficulty observing NEOs coming toward Earth from near the Sun’s direction because their close proximity to the Sun—as viewed from Earth—causes sunlight scattered by Earth’s atmosphere to be a problem and also poses risks to the telescopes when they point toward these directions. Objects remaining in those directions have orbits largely interior to Earth’s; the understanding of their number is as yet very uncertain. In addition, there are objects that remain too far from Earth to be detected almost all of the time. The latter include Earth-approaching comets (comets with orbits that approach the Sun at distances less than 1.3 astronomical units [AU] and have periods less than 200 years), of which 151 are currently known. These represent a class of objects probably doomed to be perpetually only partly known, as they are not likely to be detected in advance of a close Earth encounter. These objects, after the completion of exhaustive searches for NEOs, could dominate the impact threat to humanity. Thus, assessing the completeness of the NEO surveys is subject to uncertainties: Some groups of NEOs are particularly difficult to detect. Asteroids and comets are continually lost from the NEO population because they impact the Sun or a planet, or because they are ejected from the solar system. Some asteroids have collisions that change their sizes or orbits. New objects are introduced into the NEO population from more distant reservoirs over hundreds of thousands to millions of years. The undiscovered NEOs could include large objects like 2009 HC82 as well as objects that will be discovered only months or less before Earth impact (“imminent impactors”). Hence, even though 85 percent of NEOs larger than 1 kilometer in diameter might already have been discovered, and eventually more than 90 percent of NEOs larger than 140 meters in diameter will be discovered, NEO surveys should nevertheless continue, because objects not yet discovered pose a statistical risk: Humanity must be constantly vigilant. Finding: Despite progress toward or completion of any survey of near-Earth objects, it is impossible to identify all of these objects because objects’ orbits can change, for example due to collisions. Recommendation: Once a near-Earth object survey has reached its mandated goal, the search for NEOs should not stop. Searching should continue to identify as many of the remaining objects and objects newly injected into the NEO population as possible, especially imminent impactors.
Despite these failures feasible solutions exist—this outweighs all other impacts
POLYCAPITALIST 10-28-2010 (I am an independent investor with private sector experience in investment banking, strategy consulting and venture capital. I have worked with both multinationals and startups, and I have served on the board of directors of both publicly traded and private companies. My academic training consists of graduate/postgraduate studies in accounting, finance and economic history. “Cheap Insurance Against the Ultimate Black Swan,” http://seekingalpha.com/instablog/489997-the-polycapitalist/105674-cheap-insurance-against-the-ultimate-black-swan)
I thought it could be a nice, light distraction to write about the greatest known threat to life on earth. What is it? Global warming, infectious disease, and thermonuclear war are some of the more common answers to this question. However, there is another threat of perhaps even greater danger which doesn't receive nearly as much airtime, or resources devoted to its prevention. Former astronaut Russell Schweickart recently penned a NY Times piece on the very real risks posed by asteroids to life on earth. I had the pleasure of meeting Mr. Schweickart several years ago, and he is generally considered the leading advocate for increasing awareness and addressing this threat. Asteroids -- as any T-Rex fan will attest -- can be absolutely devastating. Strong scientific evidence suggests that 65 million years ago an asteroid of approximately seven to eight miles in diameter struck near Mexico and wiped out the dinosaurs and over half of all species. It doesn't take an eight mile asteroid to cause significant damage. The 'Tunguska event', which featured an asteroid with a diamater of only 120 feet, leveled approximately 800 square miles of (thankfully) relatively empty Siberian forest. An asteroid much smaller than Tunguska could hit a heavily populated area and cause a loss of life in the millions. Can Anything Be Done? There is some good news. We already possess the technical knowledge to prevent asteroid impact. We can detect asteroids that may collide with earth, sometimes up to a decade in advance of potential impact. We also know what to do once we've spotted one that's on a collision course with our planet. One option can be described simply as using a spacecraft to "rear-end" the asteroid. This alters the asteroid's trajectory away from earth. The bad news is that we are not investing the relative pittance it would take to mitigate asteroid impact risk. Schweickart estimates that it would cost roughly $250-$300 million over the next 10 years to track all asteroids and fully develop the deflection capability. Annual maintenance expense for the program would be $50-$75 million. These figures represent a small fraction of the U.S. federal budget. So, the choice is pretty clear. We can either spend a few hundred millions dollars and mitigate asteroid risk. Or we can continue to roll the dice risking perhaps all life on earth.