Did a triple - or even quadruple - whammy kill the dinosaurs?

Linda and I were among the happy few people I know who actually watched as, day by day, fragments of the comet Shoemaker-Levy slammed into Jupiter. Using a 5" refractor, we were able to plainly see the huge scars the comet's impacts left in the upper atmosphere of the giant planet. It occurred to me at the time that such a series of impacts on the Earth would be a good candidate for the event that wiped out three quarters of our planet's the plant and animal species 65 million years ago.

A few years back I wrote a series of articles and, eventually, a book suggesting that multiple impacts by cometary fragments would be much more likely to result in a sudden global extinction than would a single asteroidal impact.

At the time it wasn't universally acknowledged that even one impact had occurred at the time of the K-T / K-P extinction (Cretaceous - Tertiary / Palaeogene) Recent investigation, however, seems to suggest that there were three, perhaps four impacts at the time:

• Chicxulub, on the Yucatan Peninsula, Mexico
• Boltysh: a large crater in the Ukraine
• The Shiva Structure off the west coast of India
• The Silverpit crater in the North Sea

The Shiva and Silverpit structures are not yet acknowledged by everyone as impact craters, but both have their supporters. (Some evidence suggests that Silverpit may be slightly later)

If even just the Chicxulub and Boltysh Craters were made within a short space of time, this would be very strong evidence that it was a number of cometary fragments rather than an asteroid that was responsible for this - and probably other - global extinction events.