International Journal of Astrobiology

Did a gamma-ray burst initiate the late Ordovician mass extinction?

A.L. Melott a1, B.S. Lieberman a2, C.M. Laird a1, L.D. Martin a3, M.V. Medvedev a1, B.C. Thomas a1, J.K. Cannizzo a4, N. Gehrels a4 and C.H. Jackman a5
a1 Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 USA e-mail:
a2 Departments of Geology and Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
a3 Museum of Natural History, University of Kansas, Lawrence, KS 66045, USA
a4 Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA
a5 Laboratory for Atmospheres, NASA Goddard Space Flight Center, Code 916, Greenbelt, MD 20771, USA

Article author query
melott a   [PubMed][Google Scholar] 
lieberman b   [PubMed][Google Scholar] 
laird c   [PubMed][Google Scholar] 
martin l   [PubMed][Google Scholar] 
medvedev m   [PubMed][Google Scholar] 
thomas b   [PubMed][Google Scholar] 
cannizzo j   [PubMed][Google Scholar] 
gehrels n   [PubMed][Google Scholar] 
jackman c   [PubMed][Google Scholar] 


Gamma-ray bursts (GRBs) produce a flux of radiation detectable across the observable Universe. A GRB within our own galaxy could do considerable damage to the Earth's biosphere; rate estimates suggest that a dangerously near GRB should occur on average two or more times per billion years. At least five times in the history of life, the Earth has experienced mass extinctions that eliminated a large percentage of the biota. Many possible causes have been documented, and GRBs may also have contributed. The late Ordovician mass extinction approximately 440 million years ago may be at least partly the result of a GRB. A special feature of GRBs in terms of terrestrial effects is a nearly impulsive energy input of the order of 10 s. Due to expected severe depletion of the ozone layer, intense solar ultraviolet radiation would result from a nearby GRB, and some of the patterns of extinction and survivorship at this time may be attributable to elevated levels of UV radiation reaching the Earth. In addition, a GRB could trigger the global cooling which occurs at the end of the Ordovician period that follows an interval of relatively warm climate. Intense rapid cooling and glaciation at that time, previously identified as the probable cause of this mass extinction, may have resulted from a GRB.

(Published Online August 5 2004)
(Received January 12 2004)
(Accepted April 12 2004)

Key Words: Population and evolution; mass extinction; gamma-ray burst; Ordovician; ultraviolet ozone.