Dinosaur Killer - Four Revolutions in the Earth Sciences - page 182

invite investigation of this feature in the light of the meteorite impact-climatic al-
teration hypothesis for the late Cretaceous extinctions.” 12
The science reporter for the Houston Chronicle interviewed Penfield and
Camargo in late 1981 and wrote a front-page article about their report. 13 In March
1982, the magazine Sky and Telescope published an account of the Penfield-
Camargo finding entitled “Possible Yucatán Impact Basin.” It included this state-
ment: “Penfield . . . believes the feature, which lies within rocks dating to Late
Cretaceous times, may be the scar from a collision with an asteroid roughly 10
km across.” 14 But in spite of these prominent articles, neither the proponents nor
the opponents of the Alvarez theory followed up, and the Chicxulub crater had to
be rediscovered a decade later. As we have seen and will see, this is not the only
time that scientists have overlooked a report that they should have taken to heart.
It seems likely that most continued to accept the Chicxulub structure as volcanic;
after all, it was buried beneath half a mile of younger rocks and thus hard to be
sure about.
To test whether Chicxulub was indeed an impact structure, in 1981 William
Phinney of the Johnson Space Center urged Penfield to find samples from the
deep exploration wells that PEMEX, the Mexican oil giant, had drilled in the early
1950s. Despite searching at PEMEX and revisiting the Chicxulub well site, Pen-
field was unable to locate the samples until a decade later, when he finally found
them in storage at the University of New Orleans.
At a 1991 conference, David Kring, Hildebrand, and Boynton presented the res-
ults of a microscopic study of the Chicxulub drill cores. They found quartz that
had undergone high-pressure shock and a rock that they interpreted as an impact
melt, similar to the suevite that Shoemaker had identified at the Rieskessel. “The
Chicxulub structure is probably an impact crater,” they concluded. 15 In a paper in
Geology later that year, the three, together with Penfield and others, followed up
with detailed evidence to back up their conclusion. 16 Surely the discovery of the
Crater of Doom would silence the critics of the Alvarez theory—or would it?