Sky.and.Telescope_

28 August 2014 sky & telescope

History of Astronomy

the centennial of the

outbreak of World War I. At the time, astronomers were

still debating the origin of the Moon’s craters, but most

thought they were volcanic rather than impact features.

In part, this was because no examples of comparable fea-

tures formed by impact on Earth were defi nitively known.

Even Coon Butte in Arizona had been declared a maar,

a volcanic feature produced by a steam explosion, by the

great Grove Karl Gilbert of the U.S. Geological Survey.

This august marks

Scientist

Who Solved

Lunar Craters

By studying World War I battlefi elds,

Charles Gifford developed the theory

that lunar craters were formed by impacts.

But not everyone agreed. In particular, Harvard-

trained mining geologist Daniel Moreau Barringer

presented convincing evidence by 1909 that it had been

formed by a meteorite impact. He was eventually vindi-

cated, and Meteor Crater remains the fi rst-established and

best-known meteorite-impact feature on Earth.

There was one primary objection to the meteorite-

impact theory for lunar craters, which had been proposed

by a number of investigators since the early 19th century.

William Sheehan

The Forgotten