No. 54: Nov-Dec 1987
The impact/extinction controvery still rages. A careful evaluation of paleontological evidence has persuaded catas trophists to think in terms of comet showers spread out over a few million years, rather than a single impact per extinction. This short abstract from a Nature article says it all:
"If at least some mass extinctions are caused by impacts, why do they extend over intervals of one to three million years and have a partly stepwise character? The solution may be provided by multiple cometary impacts. Astronomical, geological and palaeontological evidence is consistent with a causal connection between comet showers, clusters of impact events and stepwise mass exi tinctions, but it is too early to tell how pervasive this relationship may be."
(Hut, Piet, et al; "Comet Showers as a Cause of Mass Extinctions," Nature, 329:118, 1987.)
Comment. In other words, the nature of astronomical catastrophism is still up in the air! But, bear in mind that a mere decade ago such a paper would have to look far for a jounal that would publish it.