[ForGod'sSake]

Buy it.< P> Well, OK.

Anyway, an item of curiousity for me is the apparent nastiness visited around Alaska at about the same time(I suspect other places will be discovered). Now, it seems catastrophic events are fairly rare and it would be quite the coincidence if our little planet were to experience two in a relatively short period of time. That is, a supernova's blast reaching us at roughly the same time as an impact from a comet/whatever. A single event is more likely -- whatever it was.

The evidence of gamma ray bombardment I gather is not in dispute? I don't know if it's been pointed out but I found THIS PIECE whilst looking for alternative sources for gamma rays:

BATSE requirements for a colliding comet source of gamma-ray bursts

R. Stephen White

Institute of Geophysics and Planetary Physics, University of California, Riverside, California 92521

The BATSE and Venera results place tight restrictions on possible sources of Gamma Ray Bursts, GRB. Collisions of magnetized comets in the solar system appear to satisfy the conditions of the observed isotropic direction distribution and the measured N(P_max) vs P_max distributions where X is fluence, flux, maximum flux or ratio of count rate at maximum to the threshold count rate. The distances to the bursts (GRB comet cloud), and density of comets is tailored to the observed data. To satisfy observations of N(P_max) vs P_max for the maximum gamma ray fluxes, P_max10^–5 erg cm^–2 s^–1 (about 30 bursts yr^–1), the comet density, n, should increase as n~a¹ from about 40 to 100 AU where a is the comet heliocentric distance. The turnover above 100 AU requires n~a^–1/2 to 200 AU to fit the Venera results and n~a^1/4 to 400 AU to fit the BATSE data. the masses of comets are from: 40–100 AU, about 9 earth masses, m_E; 100–200 AU about 25 m_E; and 100–400 AU, about 900 m_E. The spherical GRB comet cloud is neither the Oort Cloud nor the Kuiper Belt. Current minimum distances to bursts determined from time of arrival of the interplanetary network in combination with Watch on Ulyssus or Comptel or EGRET on CGRO neither verify nor prohibit this burst source. The gamma ray burst flux of 10^–5 erg cm^–2 s^–1 corresponds to a luminosity at 100 AU of 3±10²⁶ erg s^–1. Two colliding Halley's comets at a distance of 100 AU have a combined kinetic energy of 3±10²⁸ erg, a factor of about 100 greater than required by the bursts. Betatron acceleration in the compressed magnetic fields between the colliding comets could accelerate electrons to energies sufficient to produce the observed high energy gamma rays by Bremsstrahlung. Many of the observed features of gamma ray bursts can be explained by the solar comet collision source. ©1994 American Institute of Physics.

...which discusses comet collisions as a viable source. Impacting our atmosphere might work the same way???

I suppose the question is, if the P/H extinctions were caused by a single event, which is most likely?

Gotta run and see about actually getting some work done ;^)

[SunkenCiv]

it seems catastrophic events are fairly rare and it would be quite the coincidence if our little planet were to experience two in a relatively short period of time. That is, a supernova's blast reaching us at roughly the same time as an impact from a comet/whatever. A single event is more likely -- whatever it was.

I wholeheartedly agree. The comet was also debris from the explosion, either directly or indirectly; either the comet made the whole trip, or was pushed by the actual debris into the inner Solar System.