TUNGUSKA IMPACTOR SIZE REVISION
The 1908 Tunguska airburst from a small asteroid has generally been estimated to have had an energy of 10-15 megatons. The corresponding size for a rocky impactor is roughly 60 meters in diameter. Mark Boslough of Sandia Laboratory, however, has generated new supercomputer simulations that suggest a smaller Tunguska explosion. In part his models require less energy in the explosion because he includes the substantial downward momentum of the rocky impactor, rather then modeling it as a stationary explosion. If this revision (down to an estimated energy of 3-5 megatons, and a corresponding diameter perhaps as low as 40 m) is correct, the expected frequency of such impacts changes, from once in a couple of millennia to once in a few hundred years. If smaller impactors can do the damage previously associated with larger ones, of course, the total hazard from such impacts is increased. Below is a press release from Sandia and a newspaper article discussing this new work.
News Article: Tunguska Revision, and a Possible NEA Impact on Mars
