International Journal of Astrobiology

Oceanic hypervelocity impact events: a viable mechanism for successful panspermia?

D.J. Milner a1, M.J. Burchell a1, J.A. Creighton a1 and J. Parnell a2
a1 Centre of Astrophysics and Planetary Science, University of Kent, Canterbury, Kent CT2 7NH, UK e-mail:
a2 Geosciences School, Geology and Petroleum Geology, University of Aberdeen, Aberdeen, UK

Article author query
milner dj   [PubMed][Google Scholar] 
burchell mj   [PubMed][Google Scholar] 
creighton ja   [PubMed][Google Scholar] 
parnell j   [PubMed][Google Scholar] 


The idea that life migrates naturally between planetary bodies has grown in strength in recent years. This idea (panspermia) is believed to be possible via the mechanism of impact events. Previous research on this topic has concentrated on small meteoroids (micrometres to centimetres in diameter), with giant objects (metres to kilometres in diameter) being relatively ignored. This is due to the common belief that the larger objects vaporize on impact with the Earth's surface, which in most studies is taken as rock. Here we examine experimentally whether hypervelocity impacts into water result in significant survival of the impactors. For this study the University of Kent's two-stage light gas gun was used to accelerate millimetre-sized shale projectiles obliquely into a relatively deep water layer, at approximately 5 km s−1. Two shots have been made with surviving fragments being recovered from each. The surviving fragments appear highly shocked and display clear signs of cracking. The fragments that have been isolated contribute to a significant percentage (~10%) of the original unfired projectile mass and are as large as ~20% of the original projectile diameter. This indicates that oceanic hypervelocity impact events of large asteroids may deliver significant volumes of solid material to the Earth and thus provide a possible mechanism for successful panspermia.

(Published Online October 16 2006)
(Received June 27 2006)
(Accepted August 28 2006)

Key Words: oceanic hypervelocity impacts; panspermia; projectile fate.