- Edward C. T. Chao
Edward C. T. Chao (Edward Ching-Te Chao) (
November 30 ,1919 –February 3 ,2008 ) was one of the founders of the field of impactmetamorphism , the study of the effects ofmeteorite impacts on the Earth's crust.Born in
Suzhou ,China , he was best known for discovering two high-pressure forms ofsilica in nature,coesite andstishovite .Career
Chao came to the
United States in 1945 to teach Chinese to American troops. He then attended theUniversity of Chicago and was granted a PhD in geology in 1948. In 1949, he was employed by theUnited States Geological Survey (USGS), where he spent his entire professional career until retiring in 1994.Scientific contributions
Chao worked on a variety of topics over the course of his USGS career, including
engineering geology ,economic geology , andcoal petrology . However, he was best known for his work on impactgeology andtektite s. Shortly after he began work on tektites in 1960, Chao was given a sample ofsandstone from the vicinity ofMeteor Crater ,Arizona . From this material, he was able to isolate an unusualmineral with highrefractive index , which he showed to be a high-pressurepolymorph ofsilicon dioxide . He named the new mineralcoesite in honor of the scientist who had synthesized the same phase in the laboratory seven years earlier [E. C. T. Chao, E. M. Shoemaker, and B. M. Madsen (1960) First Natural Occurrence of Coesite. Science 132, no. 3421, pp. 220-222 [http://www.sciencemag.org/cgi/content/abstract/132/3421/220] ] [Schaber G.G. (2005) The U.S. Geological Survey, Branch of Astrogeology—A Chronology of Activities fromConception through the End of Project Apollo (1960-1973). USGS Open-file report 2005-1190 [http://pubs.usgs.gov/of/2005/1190/of2005-1190.pdf] ] . Several years later, Chao found a second high-pressure polymorph of silica in these rocks. It too had been previously synthesized in laboratory studies, but was not known to occur in nature. He named this mineralstishovite in honor of the person who had first made it, Russian physicist,Sergei Stishov [Chao, E.C.T. et al (1962), Stishovite, a very high pressure new mineral from Meteor Crater, AZ, Journal of Geophysical Research: 67: 419-421.] . Coesite and stishovite became known as hallmarks ofimpact crater events, which were essentially the only natural processes that produced high enoughpressure s to transform ordinaryquartz into both of thesedense minerals. Chao went on to find coesite and stishovite in rocks from theRies Crater inBavaria ,Germany , establishing that this structure was also produced by impact cratering.Chao made many pioneering studies on tektites, and discovered the occurrence of
iron -nickel metal in specimens from thePhilippines . This helped establish that tektites were produced inmeteorite impacts. He also recognized that tektites showed evidence for passage through Earth's atmosphere, which led him to the conclusion that the impacts responsible for tektites occurred on theMoon , a view that is no longer widely held among scientists.His work on
moon rocks included being a member of preliminary examination teams anda principal investigator during the Apollo 11-17 research programs.Honors
Chao received the Wetherill Medal from the
Franklin Institute and, in 1992, theBarringer Medal from theMeteoritical Society for his work in impact geology. He was a recipient of the Alexander von Humboldt Foundation Senior U.S. Scientist Award, and had an asteroid named for him,3906 Chao . The mineralchaoite , an impact-produced form ofcarbon discovered at the Ries Crater, was also named in his honor.References
External links
* [http://www.washingtonpost.com/wp-dyn/content/article/2008/02/08/AR2008020803834.html Washington Post obituary]
* [http://blog.washingtonpost.com/postmortem/2008/02/hidden_stories.html Story on naming of stishovite]
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