Edward Chao
The mineralogist who found coesite at Meteor Crater in 1960, the first proof that a crater on Earth was made by an impact.
Key facts
- Born
- 1919
- Died
- 2008
- Nationality
- Chinese-born American
- Field
- Mineralogist
Edward Ching-Te Chao was born in China and moved to the United States to study geology. He joined the US Geological Survey, where he worked on the minerals in rocks under extreme conditions.
In 1953 chemists had made coesite, a dense form of silica, by squeezing quartz at enormous pressures, far higher than in the Earth's crust. Eugene Shoemaker suspected that such a mineral might form when a meteorite strikes. In 1960 Chao examined sandstone from Meteor Crater in Arizona and identified natural coesite in it for the first time.
The discovery gave geologists a test for impacts. Coesite cannot form in ordinary volcanic or tectonic processes near the surface, so finding it is a fingerprint of the shock wave of an impact. A year later Chao and Shoemaker found coesite in rocks from the Nördlinger Ries in Germany, proving that it too was an impact crater. Chao also helped identify stishovite, an even denser form of silica, in nature.
Later, Chao studied lunar rocks brought back by the Apollo missions and described their shock effects. His work turned the study of impact craters on Earth into a precise science.
On the timeline
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Barringer Crater (Meteor Crater) craterNördlinger Ries crater