Thomas J. Ahrens, 74

Thomas J. Ahrens, the Fletcher Jones Professor of Geophysics, Emeritus, at Caltech, died at his home in Pasadena on November 24. He was 74. An expert in the behavior and properties of rocks and minerals undergoing shock compression, Ahrens studied the dynamics of high-pressure materials inside Earth and other planets. His research also included planetary impacts and the formation of craters and planets. "Tom was both a highly productive and broadly knowledgeable scientist and a dedicated mentor to dozens of students, postdocs, and visitors who now fill the ranks of mineral physics positions at universities around the world," says Professor of Geology and Geochemistry Paul Asimow, who credits Ahrens as his most important mentor while Asimow was a junior faculty member at Caltech. Together, they ran the Lindhurst Laboratory of Experimental Geophysics, which Ahrens built in 1974 when the Seismological Laboratory moved to South Mudd. "Our relationship was symbiotic," Asimow says.