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Terrestrial Ozone Depletion due to a Milky Way Gamma-Ray Burst

Thomas, B. C., C. H. Jackman, A. L. Melott, C. M. Laird, R. Stolarski, N. Gehrels, J. K. Cannizzo, and D. P. Hogan (2005), Terrestrial Ozone Depletion due to a Milky Way Gamma-Ray Burst, The Astrophysical Journal, 622, L153-L156.

Based on cosmological rates, it is probable that at least once in the last gigayear the Earth has been irradiated by a gamma-ray burst (GRB) in our Galaxy from within 2 kpc. We have performed the first detailed computation of the effects on the Earth’s atmosphere of one such impulsive event: A 10 s 100 kJ mϪ2 burst penetrates to the stratosphere causing globally averaged ozone depletion of 35%, with depletion reaching 55% at some latitudes. Significant depletion persists for over 5 years after the burst. A 50% decrease in ozone column density leads to approximately 3 times the normal UVB (280–315 nm; a wavelength band that ozone significantly absorbs and that living organisms are sensitive to) flux, and widespread extinctions are likely, based on extrapolation from sensitivity of modern organisms. Additional effects include a shot of nitrate fertilizer and NO2 opacity in the visible, providing a cooling perturbation to the climate over a similar timescale. These results lend support to the hypothesis that a GRB may have initiated the late Ordovician mass extinction (Melott et al.). Subject headings: astrobiology — gamma rays: bursts Online material: color figures, mpeg animation

Research Program: 
Atmospheric Composition Modeling and Analysis Program (ACMAP)