|Speaker||Talk Date||Talk Series|
|Dave Dearborn (Austin)||11 August 2010||Institute of Astronomy Seminars|
By early 2010, NASA's Spaceguard Survey expanded our solar system's membership by about 500,000 asteroids, of which 6758 are classified as Near Earth Objects (NEOs), and 1086 as Potentially Hazardous Objects (PHOs). More than 200 of these PHOs currently have a small but finite probability of impacting the earth in the next 100 years. We now know that every couple of years, a celestial body impacts the earth with energy near that of the Hiroshima bomb. Fortunately, that energy is usually deposited high in the atmosphere and causes little damage, but on longer timescales, impacts occur with the potential to destroy regions, or whole civilizations.