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Observatory, 125, 319322, 2005 EARTH IN THE COSMIC SHOOTING GALLERY

Summary: Observatory, 125, 319322, 2005
By D.J. Asher1, Mark Bailey1, Vacheslav Emel'yanenko2 and Bill Napier3
1Armagh Observatory, College Hill, Armagh, BT61 9DG
2South Ural University, Chelyabinsk, 454080, Russia
3Cardiff Centre for Astrobiology, Cardiff University, Cardiff CF10 3DY
The terrestrial impact rate appears to be substantially higher than cur-
rent near-Earth object population models imply, consistent with a signifi-
cant unseen cometary contribution to the terrestrial impact hazard.
As a result of a growing number of asteroid and comet discoveries in recent years by dedicated
`Spaceguard' survey programmes aimed at finding Near-Earth Objects (NEOs) on potentially
Earth-colliding trajectories, and as a result too of improved dynamical modelling of the NEO
population, the impact rate by NEOs of various sizes is thought to be fairly well constrained.
The problem can be approached in at least three ways. One is simply to model the whole
population of potential impactors, based on objects discovered during large-scale surveys1,2. A
second is to consider the cratered surfaces of the Earth and Moon, and estimate the flux of
different-sized projectiles by counting craters3,4. A third is to focus attention on objects that
happen to pass very close to Earth. Although there are relatively few such objects, this method
has the advantage of constraining the flux of relatively small and/or faint objects. Moreover,


Source: Armagh Observatory


Collections: Physics