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There are many species ending (i.e., the extinction of mankind) catastrophe scenaria. Many people agree that the most likely is the collision of a 10-kilometer or greater diameter asteroid with Earth (estimated annual risk is 10^-8). Other scenaria include pandemics, global warming, and technology itself turning on its creators.

Some potential catastrophes are particularly novel. One of these is based on the production of ( hypothetical ) strangelets at high-energy colliders. If high-energy collisions can produce negatively charged strangelets with long enough half-lives to interact with the protons, the act of one strangelet colliding with an atom’s nucleus could catalyze its conversion to strange matter. This would release energy and produce a larger, more stable strangelet. If this new strangelet, in turn, collides with another nucleus, it could repeat this process, and a chain reaction could ensue. Ultimately, the nuclei of all the atoms of Earth would be converted to a lump of strange matter.

“A critical look at risk assessments for global catastrophes,” by Adrian Kent ( Risk Analysis, Vol. 24, No. 1, 2004. Also see http://arxiv.org/abs/hep-ph/0009204v6 ) offers an interesting discussion of this novel risk. He argues that the imputed risk assigned to this potential catastrophe is 2 x 10^-8 over the ten-year experiment’s life. He goes on the describe that consequences and cost-benefit were never considered in the determination of risk and its acceptability, and he argues for a more reasoned, objective risk analysis process in the future ( e.g., not totally directed by stakeholders ). Kent’s conclusion that “[f]uture policy on catastrophe risks would be more rational, and more deserving of public trust, if acceptable risk bounds were generally agreed ahead of time and if serious research on whether those bounds could indeed be guaranteed was carried out well in advance of any hypothetically risky experiment, with the relevant debates involving experts with no stake in the experiments under consideration” is certainly reasonable.