Summary: Mon. Not. R. Astron. Soc. 000, 000--000 (0000) Printed 13 June 2001 (MN L A T E X style file v1.3)
NEO velocity distributions and consequences for the
Chicxulub impactor
S.V. Jeffers 1;2 , S.P. Manley 1 , M.E. Bailey 1 and D.J. Asher 1
1 Armagh Observatory, College Hill, Armagh, BT61 9DG
2 School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS
last update 2001 May 3
ABSTRACT
An ¨
Opik based geometric algorithm is used to compute impact probabilities and veloc­
ity distributions for various near­Earth object (NEO) populations. The resulting crater
size distributions for the Earth and Moon are calculated by combining these distri­
butions with assumed NEO size distributions and a selection of crater scaling laws.
This crater probability distribution indicates that the largest craters on both the Earth
and the Moon are dominated by comets. However, from a calculation of the fractional
probabilities of iridium deposition, and the velocity distributions at impact of each
NEO population, the only realistic possibilities for the Chicxulub impactor are a short­
period comet (possibly inactive) or a near­Earth asteroid. For these classes of object,
sufficiently large impacts have mean intervals of 100 Myr and 300 Myr respectively,
slightly favouring the cometary hypothesis.

Source: Armagh Observatory

Collections: Physics