The Moon’s Face - Four Revolutions in the Earth Sciences - page 156

our desperate experiments with which we try to establish an equality between the
Moon and the Earth” (221).
Like Gilbert, Wegener realized that if impact craters and their debris blanket the
Moon, so must they have once blanketed the Earth. Yet as of the 1920s, geologists
had not identified a single terrestrial impact crater and even the prime candidate,
Meteor Crater, Gilbert had declared to be volcanic. Wegener not only espoused an
impact origin for Meteor Crater, he recognized that “it is highly improbable that
this is the only meteorite crater on Earth.” It seemed to him that “similar magnifi-
centmeteoriteimpactsoccurredrepeatedly,atleastinlatergeologichistory(230).”
Gilbert had said essentially the same thing, but excluded Meteor Crater.
But even these were not the most insightful of Wegener's conclusions. Again
like Gilbert, he realized that his observations led back to the Moon's origin:
The Moon itself was built [from] an accretion of a large number of firm bodies whose paths
were going around the Sun and were close to each other. After some time, all of the available
large objects were consumed and the rate of the process slowly declined. During the culmina-
tion point, impacting was so rapid that the temperature of the bulk of the Moon rose over the
melting point of the rocks. But in the last phase of the process radiation again prevailed and
the new impacts found the seas totally solidified.
(233)
Though Wegener claimed that continental drift was obvious, still it depended on
the interpretation of complex geology. Not so the Moon. Like Gilbert, Wegener
merely looked up, reported what he saw, and drew logical conclusions. Any open-
minded selenologist ought to have given serious consideration to Wegener's ideas
about the Moon. But whereas continental drift eventually drew a great deal of at-
tention, even though most of it led to opposition, Wegener's paper on the origin
of lunar craters vanished with hardly a trace. Wegener was right about drift, right
abouttheoriginoflunarcraters,andheadedintherightdirectionabouttheMoon's
origin. The failure of scientists to heed Alfred Wegener cost both geology and lun-
ar science a half-century of progress.
Cosmic Rather Than Volcanic
The Moon was Robert Dietz's first scientific love. 3 His interest began in high
school when he dreamed of becoming an astronomer, the career of astronaut hav-
ing not yet been invented. As a student at the University of Illinois, Dietz took the
only two astronomy courses available. When it came time to write his Ph.D. thes-
is, he proposed to study the Moon's surface features, but his professors turned him
down, joking that no one would be able to check his fieldwork. 4