Potential impact events from Near-Earth objects Edit
Near-Earth objects (NEO) are comets, asteroids (>50 meters diameter) and large meteoroids (<50 meters diameter) whose orbit intersects Earth's orbit and which may therefore pose a collision danger.
As of May 2006, NASA has catalogued 57 Near-Earth comets (NEC) and 3999 Near-Earth asteroids (NEA) of which 834 asteroids have diameters greater than 1 kilometer. The rate of detection is about 500 NEOs per year.
Asteroid VD17 - (0.58 km dia.) Current estimates give the asteroid about a 1 in 1,800 chance that it will collide with Earth on May 4, 2102. If that happens, the energy released by the impact would be an estimated 15,000 megatons of TNT, and result in at least regional scale devastation. The asteroid is ranked 2 on the Torino impact hazard scale, currently the highest ranked object tracked by the NASA NEO Program.
Asteroid 99942 Apophis (0.32 km dia.) is ranked 1 on the Torino impact hazard scale. A number of impacts are possible between the years 2036-2054 (April 13, 2036 being the most likely). As of April 2006, this corresponds to a cumulative impact probability of 1 in 6,250. A NASA estimate places the probable impact energy at 880 megatons of TNT. (The 1883 eruption of Krakatoa was the equivalent of roughly 200 megatons.)
Earth Impact Effects Program An interactive web site for estimating the regional environmental consequences of an impact on Earth. This program will estimate the ejecta distribution, ground shaking, atmospheric blast wave, and thermal effects of an impact as well as the size of the crater produced.