I haven't found anything on line about it yet, but I heard on the television today that in analyzing the Yucatan crater, they've determined that the impact occurred hundreds of thousands of years before the dino extinction, so the original Alverez theory may not be true.

On the other hand, much closer to home, both in distance and time, a paper presented at last week's planetary defense conference speculates that a comet may have caused the Chicago Fire.

Well, that would let Mrs. O'Leary's cow off the hook. Bossy may be exonerated after all these decades.

Either way, it would still be prudent to keep looking for them and to quickly develop the technological capability needed to deal with any that appear to have our number.

The cow story is not generally taken seriously in Chicago, altho the Fire Acadamy is located at the site of the O'Leary residence. The Chicago fire was in fact the second worst fire that day. The fire in Peshtigo Wisconsin was both deadlier and more destructive; when my wee wifey was a cabinetmaker's apprentice she was told that it is still effecting lumber prices.

When one looks at a map of the various fires that day, including smaller ones in Michigan, the comet theory looks reasonable indeed.

Because it occurred on the same night as Chicago's more famous blaze, the deadliest forest conflagration in American history is not well known. Gess and Lutz estimate that about 2,500 people died in the Peshtigo, Wisconsin, fire of 1871, but it is impossible to know the death toll with certainty because the destruction was so complete and the first-person accounts so sparse. Yet the authors creditably reconstruct the extant testimony into a moving narrative of the calamity and its causes. As aficionados of disaster tales appreciate, our attraction to such stories derives in part from incredulity at the element of human complacency or folly involved: at Peshtigo, the rampant logging of the latter 1800s left combustible litter everywhere. An ignored harbinger of doom was smoke wafting eastward from Minnesota prairie fires, accompanied by an increasingly ruddy western sky. Quickening their narrative with an approaching cyclonic weather system, the authors sketch people dropping their daily tasks to attempt to escape from the roaring flames and fireballs. An ably crafted addition to disaster tales that is not for the faint-hearted. Gilbert Taylor
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See! - - > Rampant logging and littering. Where was Ralph Nader when they needed him?

There would need to be some very solid research to pin things down that close. At roughly 65,000,000 years, 300,000 years is a small margin of error - fossils get mixed slightly in soil, as do minerals deposited due to impact. I'd need to see several studies by big names providing good evidence before I took it seriously.

The main evidence for this conclusion is that right at the impact site there is a thick layer of material (which would otherwise correspond to approximately 300,000 years of buildup) between the impact crater layer and the K-T boundary. These folks surmise that this is direct proof that the Chicxulub impact occured several hundred thousand years before the mass extinction event which marks the boundary between the Cretatious and Tertiary Eras (the K-T boundary). The more rational explanation is that this material represents rapid infill due to the backwash from the mega-tsunami created by the impact.

NationalGeographic.com has a good summary of the findings and debate. Essentially, the theory is extraordinarily weak and poorly supported at this point.